Role of p38 in the regulation of renal cortical cyclooxygenase-2 expression by extracellular chloride

We have previously shown that in renal cortex, COX-2 expression is localized to macula densa and surrounding cortical thick ascending limb of Henle (cTALH). Dietary salt restriction increases local expression of COX-2, which mediates renin production and secretion. Given that decreased luminal chloride [Cl^–] at the level of the macula densa increases renin production and secretion, we investigated the role of extracellular ion concentration on COX-2 expression. Quiescent rabbit cTALH cells were incubated in a physiological salt solution containing high or low levels of NaCl. Immunoreactive COX-2 expression increased significantly in the low NaCl solution. COX-2 expression also increased after administration of the Na⁺/K⁺/2Cl^– cotransport inhibitor, bumetanide. Selective substitution of chloride led to increased COX-2 expression, whereas selective substitution of sodium had no effect. The p38 MAP kinase inhibitor PD169316 decreased low NaCl-induced COX-2 expression. Low-salt or low-chloride medium induced cultured cTALH to accumulate ≥ 3-fold higher levels of pp38, the activated (phosphorylated) form of p38; low-salt medium also increased pJNK and pERK levels. Feeding rats a low-salt diet for 14 days induced a significant increase in renal cortical pp38 expression, predominantly in the macula densa and cTALH. These results suggest that reduced extracellular chloride leads to increased COX-2 expression, which may be mediated by activation of a p38-dependent signaling pathway.

In the mammalian kidney, the macula densa is involved in regulation of tubuloglomerular feedback and renin release by sensing alterations in luminal chloride (1–4). To our knowledge, Kotchen et al. were the first to consider the possibility that intraluminal chloride concentrations may be the proximate mediator of macula densa regulation of renin secretion (5), and subsequent studies strongly suggested a preeminent role for extracellular chloride in macula densa regulation of renin secretion (6–8). The use of the isolated perfused juxtaglomerular (JGA) preparation provided definitive confirmation of the role of alterations of luminal chloride in regulation of renin secretion (9). Ion substitution experiments of tubular perfusate demonstrated that substitution of other cations for sodium did not affect renin secretion, whereas substitution of other anions for chloride led to increased renin secretion (10). Increasing luminal NaCl from 25 to 80 mmol/L decreased renin secretion sixfold, whereas further increases had no effect on renin secretion, indicating the t_1/2 for Cl^– to be approximately 30 mmol (8).

Macula densa sensing of luminal chloride concentration is dependent on net apical transport, mediated by the luminal Na⁺/K⁺/2Cl^– cotransport (11). The Na⁺/K⁺/2Cl^– cotransporter possesses a high affinity for Na⁺ and K⁺, such that minimal alterations in transport occur with physiological changes of Na⁺ or K⁺ concentrations; however, the affinity for chloride is lower and falls within the range of loop chloride values, thereby resulting in an uptake mechanism that is very sensitive to any change in luminal chloride (12). The role of the Na⁺/K⁺/2Cl^– cotransport in this macula densa sensing is further supported by the observation that loop diuretics, which inhibit Na⁺/K⁺/2Cl^– cotransport, increase renin activity, even in the absence of volume depletion (8, 13, 14).

Studies in experimental animals and in humans have indicated that prostaglandins are important mediators of this macula densa–regulated renin release (15–18), and studies using the isolated perfused JGA preparation demonstrated that nonselective nonsteroidal antiinflammatory drugs (NSAIDs) prevented the increases in renin release mediated by macula densa sensing of decreases in luminal NaCl (19). NSAIDs inhibit the enzymatic activity of cyclooxygenases, which prevent conversion of arachidonic acid to prostaglandin G₂ and thence to prostaglandin H₂ (20). There are two separate gene products with cyclooxygenase activity, cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). The gene for the “constitutive” cyclooxygenase, COX-1, encodes a 2.9-kb transcript, and the gene for COX-2, the “inducible” cyclooxygenase, encodes a 4.5-kb transcript and increases in response to inflammatory or mitogenic stimuli. In the kidney, COX-1 has been localized to mesangial cells, arteriolar endothelial cells, parietal epithelial cells of Bowman’s capsule, and cortical and medullary collecting ducts, but not to macula densa or cortical thick ascending limb of Henle (cTALH). In contrast, in all mammalian species examined to date (rat, mouse, dog, rabbit, human), there is localized and regulable COX-2 expression in macula densa cells and surrounding cTALH cells (21–25).

Conditions in which the macula densa has been shown to mediate renin expression and secretion, such as dietary salt deficiency, renovascular hypertension, or treatment with angiotensinogen-converting enzyme (ACE) inhibitors or with loop diuretics, all increase macula densa/cTALH COX-2 expression (21, 26–29), and COX-2–selective inhibitors blunt increases in renin in response to salt-deficient diets (30), ACE inhibition (26), and experimental renovascular hypertension (27). Direct evidence for a role of COX-2 in macula densa–mediated renin release has recently been provided by Traynor et al., who determined that in an isolated JGA preparation, increased renin release in response to lowering the perfusate NaCl concentration was blocked by a COX-2–selective inhibitor but not by a COX-1–selective inhibitor (31). Although these studies indicated that COX-2–derived prostaglandins are involved in macula densa–mediated renin release, the signals regulating COX-2 expression have not yet been determined. The present studies therefore examined whether extracellular ionic composition might influence COX-2 expression.

To determine the role of alterations in extracellular ions on expression of COX-2, quiescent cultured cTALH cells were incubated in solutions of varying ionic composition, indicated in Table 1. Immunoreactive COX-2 was expressed as the fold increase compared with quiescent control cells maintained in DME/F12.

Table 1

Composition of incubation solutions

When cTALH were incubated in low-salt medium for 6 hours, immunoreactive COX-2 expression increased significantly (3.9 ± 0.4–fold control; n = 13; P < 0.01) (Figure 1). When the cells were incubated in the same solution in which 100 mM NaCl had been added (NaCl solution), COX-2 expression was not different than in cells incubated in DME/F12 (1.1 ± 0.2–fold control; n = 5). Similarly, when 100 mM choline chloride was added (final [Cl^–] = 107 mM), COX-2 expression was not increased above base line (1.1 ± 0.3–fold control; n = 5). In contrast, when additional sodium was added with either Na gluconate or Na isethionate, COX-2 expression was significantly increased (3.1 ± 0.4– and 3.9 ± 0.6–fold control, respectively; n = 5; P < 0.01 compared with control) (Figure 1). Similar increases were seen with NaNO₃ substitution (2.5 ± 0.15–fold control; n = 3; P < 0.02 compared with control). A time course of COX-2 expression after exposure of cTALH cells to low-salt solution indicated detectable increases in expression within 1 hour, an apparent peaking within 6 hours (3.9 ± 0.4–fold control), and increased expression for up to 16 hours (3.4 ± 0.5–fold control; P < 0.01) (Figure 2).

Figure 1

Decreased extracellular [Cl^–] increases immunoreactive COX-2 (irCOX-2) expression in cultured cTAL cells. Quiescent primary cultured rabbit cTAL cells were incubated with various media (described in Table 1) for 6 hours: control, low salt, NaCl, Na gluconate, Na isethionate, and choline chloride. ^AP < 0.01 compared with control. Inset: representative experiment.

Figure 2

Time course of COX-2 expression in cTAL induced by low-salt medium. Primary cultured cTAL cells were incubated in low-salt medium for the indicated time. (n = 4–13). ^AP < 0.05, ^BP < 0.01 compared with base line. Inset: representative experiment.

To investigate whether decreases in extracellular osmolarity were involved in the increased COX-2 expression in response to low extracellular NaCl, 200 mM mannitol was added to low-salt medium. Under these conditions, COX-2 expression was still significantly increased (3.0 ± 0.1–fold control; n = 3, P < 0.05) (Figure 3). cTALH cells exposed to bumetanide (50 μM) in the NaCl solution increased immunoreactive COX-2 expression significantly (2.4 ± 0.1–fold control; n = 4; P < 0.01 compared with control) (Figure 4).

Figure 3

Effects of mannitol addition to low-salt medium. Lane 1, control; lane 2, low salt; lane 3, Low salt + NaCl; lane 4, low salt + 200 mM mannitol. ^AP < 0.01 compared with control. Inset: representative experiment.

Figure 4

Bumetanide increases COX-2 expression in cultured cTAL. Lane 1, control; lane 2, bumetanide (50 μM) in NaCl solution; lane 3, low salt. ^AP < 0.01 compared with control. Inset: representative experiment.

To identify possible signaling pathways involved in the induction of COX-2 expression by altered extracellular ionic content, cTALH cells were incubated in low-salt solution in the presence of kinase inhibitors. As indicated in Figure 5, incubation with the protein kinase C inhibitor, H7 (1 μM); the protein kinase A inhibitor, H8 (1 μM); or the adenylate cyclase inhibitor, dideoxyadenosine (100 μM), failed to attenuate significantly the elevated immunoreactive COX-2 expression (2.8 ± 0.7–, 2.8 ± 0.8–, and 3.0 ± 0.5–fold control, respectively; n = 5; P < 0.05 compared with control). In contrast, the p38 mitogen-activated protein kinase–specific (MAPK-specific) inhibitor, PD169316 (1 μM), significantly blocked COX-2 upregulation induced by low-salt medium (1.0 ± 0.3–fold control; n = 5; P < 0.05 compared with low salt only). The MEK1 inhibitor, PD98059 (1 μM), produced numerical but not statistically significant decreases in COX-2 expression (2.2 ± 0.4–fold control; n = 5; P = NS compared with low salt only).

Figure 5

The p38 specific inhibitor, PD169316, prevents increases in the COX-2 expression in cTAL cells exposed to low-salt medium. Quiescent cTAL cells were maintained in DME/F12 medium (lane 1), incubated for 6 hours in low-salt medium alone (lane 2), or in low-salt medium in the presence of MEK1 inhibitor, PD98059 (1 μM) (lane 3); p38 MAP kinase inhibitor, PD169316 (1 μM) (lane 4); PKA kinase inhibitor, H8 (1 μM) (lane 5); PKC kinase inhibitor, H7 (1 μM) (lane 6); or adenylate cyclase inhibitor, dideoxyadenosine (100 μM) (lane 7) (n = 5). ^AP < 0.01 compared with control. Inset: representative experiment.

Immunostaining with an antibody that recognizes specifically the phosphorylated form of p38 indicated that pp38 expression increased significantly in cultured cTALH incubated for 6 hours in low-salt medium (3.4 ± 0.4–fold control; n = 8; P < 0.01 compared with control) (Figure 6a). There were no increases in COX-2 expression in cells incubated in NaCl or choline chloride solutions (0.9 ± 0.1– and 1.2 ± 0.2–fold control; n = 5; P = NS compared with control), but selective removal of extracellular chloride (Na iºsethionate) induced the same increase in pp38 expression as low salt (3.3 ± 0.2–fold control; n = 5; P < 0.01 compared with control). Total immunoreactive p38 expression was unchanged (data not shown). p38 activity in cultured cTALH was also measured using ATF-2 as a substrate. p38 activity was low in cTALH in DME/F12 or NaCl or choline chloride solutions but was increased when incubated in low-salt or Na isethionate solutions (Figure 6b).

Figure 6

(a) Decreased extracellular [Cl^–] increases pp38 expression in cultured cTAL cells. Cultured cTAL cells were incubated in the indicated solution for 6 hours. (lane 1) control; (lane 2) low salt; (lane 3) Na isethionate; (lane 4) choline chloride; (lane 5) NaCl. ^AP < 0.01 compared with control; n = 5. Inset: representative experiment. (b) Decreased extracellular [Cl^-] increases p38 kinase activity in cTAL cells. cTAL cells were incubated in different media for 6 hours, and p38 kinase activity was measured as described in Methods, using ATF2 as substrate. (lane 1) control; (lane 2) low salt; (lane 3) NaCl; (lane 4) Na isethionate; and (lane 5) choline chloride. (c) Time course of pp38 expression in cTAL incubated in low-salt medium. Cells were incubated in low-salt medium 0–16 hours (n = 3). ^AP < 0.01 compared with base line. (d) Time course of pJNK and pERK expression in cTAL incubated in low-salt medium.

pp38 expression increased in response to low salt by 30 minutes, with a peak at 3–6 hours (3.0 ± 0.3–fold and 3.4 ± 0.4–fold, respectively; n = 3; P < 0.01 compared with control) (Figure 6c). Determination of the time course of expression of the activated forms of other MAPKs, activated jun kinase (pJNK) and activated ERK (pERK) indicated relatively small increases in expression above base line, with early and transient peak increases (pJNK: 1.7 ± 0.4–fold control at 30 minutes; pERK: 1.3 ± 0.1–fold control at 15 minutes; n = 3) (Figure 6d).

To determine whether alterations in p38 activity are observed in vivo in conditions in which macula densa/cTALH COX-2 expression is increased, rats were placed on a salt-deficient diet for 14 days. In renal cortex, a low-salt diet induced a significant increase in immunoreactive pp38 expression (3.9 ± 0.6; n = 3; P < 0.05 compared with control) (Figure 7). In control rat cortex, immunoreactive pp38 expression was predominantly localized to the macula densa and cTALH (Figure 8, a and c). The localization of pp38 expression was similar in the animals on a low-salt diet, but the intensity of expression was increased (Figure 8, b and d), consistent with the increases detected by immunoblotting and in a similar distribution as renal cortical COX-2 expression (Figure 8, e and f).

Figure 7

Expression of pp38 in rat renal cortex in response to dietary salt restriction. Male Sprague-Dawley rats (250 g) were maintained on normal chow or a salt-deficient diet for 14 days. Renal cortical pp38 increased significantly in low-salt rats. ^AP < 0.05 compared with control; n = 3. Inset: representative experiment.

Figure 8

Localization of pp38 in rat renal cortex in response to dietary salt. Immunoreactive pp38 expression was detected at low (×10) (a and b) and higher (×32) power (c and d) in rats maintained on normal chow (a, c, and e) or a salt-deficient diet for 14 days (b, d, and f). Note restriction of pp38 expression to cTALH and tubular expression in the animals on the salt-deficient diet (arrowheads in a and b). Low salt increased pp38 expression in macula densa and surrounding cTALH (arrows in c and d). For comparison, increased macula densa/cTALH COX-2 expression is presented (e and f). (Figure widths: a and b: 700 μm; c–f: 212 μm).

Inhibition of renin expression and secretion after administration of COX-2–selective inhibitors suggests a direct role for COX-2–derived prostanoids in renin regulation. PGE₂ and PGI₂ have been shown to mediate renin secretion in in vitro preparations (15, 16, 18, 36) and in primary cultures of juxtaglomerular cells (37), and inhibition of prostaglandin production with selective COX-2 inhibitors inhibits renin production and secretion (26, 27, 30, 31). In vitro studies in cultured mesangial cells previously demonstrated the existence of a Ca²⁺-activated Cl^– conductance and determined that decreased ambient Cl^– attenuated the responsiveness of mesangial cells to vasoactive agonists such as angiotensin II and vasopressin and increased prostaglandin and nitric oxide production (38, 39). However, in normal kidney, extraglomerular mesangial cells do not express COX-2, making it less likely that these cells are the source of the renin-regulating prostanoids. In contrast, COX-2 expression in macula densa and surrounding cTALH increases significantly in high renin states (21, 26–29).

The increase in cTALH/macula densa COX-2 expression in high renin states suggested that the signals mediating increased renin, namely decreased luminal chloride, might also be involved in mediating increased COX-2 expression. In the present studies, decreasing extracellular NaCl or selectively decreasing extracellular Cl^– stimulated COX-2 expression in cultured cTALH cells. Increased COX-2 expression was not secondary to alterations in extracellular osmolarity and could be mimicked by administration of bumetanide, suggesting that ion transport via Na⁺/K⁺/2Cl^– cotransport was involved in regulating COX-2 expression.

Studies with kinase inhibitors indicated complete inhibition of the increased COX-2 expression in response to decreased extracellular NaCl with the p38 inhibitor, PD169316 (40, 41), suggesting a role for p38 in the COX-2 regulation. Our studies further determined that pp38 expression and p38 activity increased in cultured cTALH response to low-NaCl or low-chloride media, that pp38 was localized predominantly to cTALH and macula densa in vivo, and that expression increased in animals on a low-salt diet.

Although we did not observe significant increases in ERK phosphorylation, p98059 did partially inhibit increased COX-2 expression. PD98059 has been reported to be a specific inhibitor of MEK1, which selectively activates ERKs (42). The trend toward partial inhibition with PD98059 suggests either a role for ERK activation or the possibility that in the cultured cTALH cells, PD98059 may also inhibit kinases involved in p38 and/or JNK activation or have other, nonspecific effects (43). As noted, we also observed a transient early increase in pJNK, raising the possibility that JNK may also be involved in the initial signaling to increase COX-2 expression. The lack of specific inhibitors of the JNK pathway will necessitate alternative approaches, such as transfection with dominant negative mutations, to determine definitively the role of JNK in the low Cl^–-induced activation.

The mechanism by which low ambient Cl^– activates p38 and other MAPKs in cTALH and macula densa has not yet been determined. MAPKs are activated by sequential phosphorylation of an MEK activator and an MEK (MAPK activator), which activates MAPK by dual phosphorylation of tyrosine and threonine residues (44, 45). In general ERKs regulate cell growth and differentiation and are activated by mitogens, whereas JNK and p38 pathways participate in stress responses and are activated by cellular stresses such as ultraviolet light, x-rays, free radicals, heat and osmotic shock, and withdrawal of growth factors, as well as by inflammatory cytokines such as TNF and IL-1β. (46, 47). It is noteworthy that the yeast homologue of p38, HOG, is activated by hyperosmolarity, and in mammalian cells, p38 has been shown to be activated by both hypo- and hyperosmolarity (46–49). The present studies are the first to our knowledge to demonstrate that p38 can be activated in response to altered extracellular Cl^–, even under isosmotic conditions. Increased p38 activity was observed when either relatively impermanent (isethianate, gluconate) or permeant (nitrate) anions were substituted for Cl^–.

MAPKs have been demonstrated to increase COX-2 expression in other cell types, including activation by ERKs (50, 51), JNK (51–53), and p38 (50–52, 54–56). It has been suggested that MAPKs mediate COX-2 transcription via activation of a cyclic AMP–response element (CREB) in association with either C/EBP (57) or ATF1 sites (58). In addition, p38 has also been shown to increase COX-2 expression by posttranscriptional regulation (mRNA stabilization) (56). Preliminary studies in which cultured cTALH were transiently transfected with a construct containing the mouse COX-2 promoter coupled to GFP indicate increased COX-2 transcription in response to decreased extracellular NaCl (H.-F. Cheng and R.C. Harris, unpublished results), but further studies will be required to determine mechanisms of transcriptional activation and to explore whether posttranscriptional regulation of COX-2 is also involved. Another unanswered question requiring further investigation is whether expression of other proteins important for cTALH and macula densa function, such as nNOS and ion transporters, is also regulated by p38 and/or other MAPKs. It remains possible that the observed increases in COX-2 expression may result from increased production of other mediators of COX-2 activity, such as NO (34), in addition to or instead of direct alteration of COX-2 gene transcription by p38.

Immunoisolation of cTALH cells was originally described by Allen et al. (32) and has been used to attain primary cultured cells that retain characteristics of CTLAH in vivo (26, 33, 34, 59). We have previously determined that these cells express immunoreactive COX-2 (26) and nNOS (34); however, they also express Tamm Horsfall, which is characteristic of cTALH but not macula densa cells. Although both COX-2 and nNOS are expressed by macula densa in vivo (21, 60), the surrounding cTALH are also capable of expressing both enzymes, especially in high renin states (21, 61–63). It is noteworthy that under these conditions, COX-2 expression occurs at the distal end of the loop of Henle, at the point where luminal chloride concentration is lowest. Therefore, the in vitro observation that decreased extracellular Cl^– induced increased expression of COX-2 in cTALH offers an explanation why COX-2 expression in vivo occurs at the macula densa and surrounding cTALH, the site of the thick limb with the lowest luminal NaCl concentration, and why macula densa and cTALH COX-2 expression increases with salt depletion and decreases with volume expansion.

In summary, these results suggest that alterations in extracellular chloride may increase COX-2 expression in macula densa and surrounding cTALH at least in part by increasing p38 activity. Increased COX-2 expression in these conditions may be one mechanism by which the macula densa regulates renin expression.

This work was supported by the Vanderbilt George O’Brien Kidney and Urologic Diseases Center (NIH grant DK-39261) and by funds from the Department of Veterans Affairs.

1. Persson, AEG, et al. Macula densa function. Kidney Int 1991. 32(Suppl. 32):S39-S44.
2. Schlatter, E, Salomonsson, M, Persson, AEG, Greger, R. Macula densa cells sense luminal NaCl concentration via furosemide sensitive Na⁺2C1^-K⁺ cotransport. Pflugers Arch 1989. 414:286-290.
   View this article via: PubMed CrossRef Google Scholar
3. Harris, RC. The macula densa: recent developments. J Hypertens 1996. 14:815-822.
   View this article via: PubMed CrossRef Google Scholar
4. Schnermann, J. Juxtaglomerular cell complex in the regulation of renal salt excretion. Am J Physiol 1998. 274:R263-R279.
   View this article via: PubMed Google Scholar
5. Kotchen, TA, Galla, JH, Luke, RG. Failure of NaHCO3 and KHCO3 to inhibit renin in the rat. Am J Physiol 1976. 231:1050-1056.
   View this article via: PubMed Google Scholar
6. Lorenz, JN, Weihprecht, H, Schnermann, J, Skott, O, Briggs, JP. Renin release from isolated juxtaglomerular apparatus depends on macula densa chloride transport. Am J Physiol 1991. 260:F486-F493.
   View this article via: PubMed Google Scholar
7. Scholz, H, Gotz, KH, Hamann, M, Kurtz, A. Differential effects of extracellular anions on renin secretion from isolated perfused rat kidneys. Am J Physiol 1994. 267:F1076-F1081.
   View this article via: PubMed Google Scholar
8. He, XR, Greenberg, SG, Briggs, JP, Schnermann, J. Effects of furosemide and verapamil on the NaCl dependency of macula densa-mediated renin secretion. Hypertension 1995. 26:137-142.
   View this article via: PubMed Google Scholar
9. Skott, O, Briggs, JP. Direct demonstration of macula densa-mediated renin secretion. Science 1987. 237:1618-1620.
   View this article via: PubMed CrossRef Google Scholar
10. Lorenz, JN, Weihprecht, H, Schnermann, J, Skott, O, Briggs, JP. Characterization of the macula densa stimulus for renin secretion. Am J Physiol 1990. 259:F186-F193.
    View this article via: PubMed Google Scholar
11. Salomonsson, M, Gonzalez, E, Westerlund, P, Persson, AE. Chloride concentration in macula densa and cortical thick ascending limb cells. Kidney Int 1991. 32(Suppl.):S51-S54.
12. Greger, R. How does the macula densa sense tubule function? Nephrol Dial Transplant 1997. 12:2215-2217.
    View this article via: PubMed CrossRef Google Scholar
13. Martinez-Maldonado, M, Gely, R, Tapia, E, Benabe, JE. Role of macula densa in diuretics-induced renin release. Hypertension 1990. 16:261-268.
    View this article via: PubMed Google Scholar
14. Modena, B, et al. Furosemide stimulates renin expression in the kidneys of salt-supplemented rats. Pflugers Arch 1993. 424:403-409.
    View this article via: PubMed CrossRef Google Scholar
15. Francisco, LJ, Osborn, JL, DiBona, GF. Prostaglandins in renin release during sodium deprivation. Am J Physiol 1982. 243:261-268.
16. Linas, SL. Role of prostaglandins in renin secretion in the isolated kidney. Am J Physiol 1984. 246:F811-F818.
    View this article via: PubMed Google Scholar
17. Frolich, JC, et al. Suppression of plasma renin activity by indomethacin in man. Circ Res 1976. 39:447-452.
    View this article via: PubMed Google Scholar
18. Ito, S, Carretero, OA, Abe, K, Beierwaltes, WH, Yoshinaga, K. Effect of prostanoids on renin release from rabbit afferent arterioles with and without macula densa. Kidney Int 1989. 35:1138-1144.
    View this article via: PubMed CrossRef Google Scholar
19. Greenberg, SG, Lorenz, JN, He, XR, Schnermann, JB, Briggs, JP. Effect of prostaglandin synthesis inhibition on macula densa-stimulated renin secretion. Am J Physiol 1993. 265:F578-F583.
    View this article via: PubMed Google Scholar
20. Needleman, P, Turk, J, Jakschik, BA, Morrison, AR, Lefkowith, JB. Arachidonic acid metabolism. Annu Rev Biochem 1986. 55:69-102.
    View this article via: PubMed CrossRef Google Scholar
21. Harris, RC, et al. Cyclooxygenase-2 is associated with the macula densa of rat kidney and increases with salt restriction. J Clin Invest 1994. 94:2504-2510.
    View this article via: JCI PubMed CrossRef Google Scholar
22. Komhoff, M, Seyberth, HW, Nusing, RM, Breyer, MD. Cyclooxygenase-2 expression is associated with the macula densa in kidneys from patients with Bartter like syndrome. J Am Soc Nephrol 1999. 10:437A. (Abstr.)
    View this article via: CrossRef Google Scholar
23. Komhoff, M, et al. Cyclooxygenase-2-selective inhibitors impair glomerulogenesis and renal cortical development. Kidney Int 2000. 57:414-422.
    View this article via: PubMed Google Scholar
24. Guan, Y, et al. Cloning, expression, and regulation of rabbit cyclooxygenase-2 in renal medullary interstitial cells. Am J Physiol 1997. 273:F18-F26.
    View this article via: PubMed Google Scholar
25. Khan, KN, et al. Interspecies differences in renal localization of cyclooxygenase isoforms: implications in nonsteroidal antiinflammatory drug-related nephrotoxicity. Toxicol Pathol 1998. 26:612-620.
    View this article via: PubMed Google Scholar
26. Cheng, HF, et al. Angiotensin II attenuates renal cortical cyclooxygenase-2 expression. J Clin Invest 1999. 103:953-961.
    View this article via: JCI PubMed CrossRef Google Scholar
27. Wang, JL, Cheng, HF, Harris, RC. Cyclooxygenase-2 inhibition decreases renin content and lowers blood pressure in a model of renovascular hypertension. Hypertension 1999. 34:96-101.
    View this article via: PubMed Google Scholar
28. Yang, T, et al. Regulation of cyclooxygenase expression in the kidney by dietary salt intake. Am J Physiol 1998. 274:F481-F489.
    View this article via: PubMed Google Scholar
29. Jensen, BL, Kurtz, A. Differential regulation of renal cyclooxygenase mRNA by dietary salt intake. Kidney Int 1997. 52:1242-1249.
    View this article via: PubMed CrossRef Google Scholar
30. Harding, P, et al. Cyclooxygenase-2 mediates increased renal renin content induced by low-sodium diet. Hypertension 1997. 29:297-302.
    View this article via: PubMed Google Scholar
31. Traynor, TR, Smart, A, Briggs, JP, Schnermann, J. Inhibition of macula densa-stimulated renin secretion by pharmacological blockade of cyclooxygenase-2. Am J Physiol 1999. 277:F706-F710.
    View this article via: PubMed Google Scholar
32. Allen, ML, et al. Immunodissection of cortical and medullary thick ascending limb cells from rabbit kidney. Am J Physiol 1988. 255:F704-F710.
    View this article via: PubMed Google Scholar
33. Dai, LJ, Quamme, GA. Intracellular Mg2+ and magnesium depletion in isolated renal thick ascending limb cells. J Clin Invest 1991. 88:1255-1264.
    View this article via: JCI PubMed CrossRef Google Scholar
34. Cheng, H-F, Wang, J-L, Zhang, MZ, McKanna, JA, Harris, RC. Nitric oxide regulates renal cortical cyclooxygenase-2 expression. Am J Physiol Renal Physiol 2000. 279:F122-F129.
    View this article via: PubMed Google Scholar
35. Sheikh-Hamad, D, et al. p38 kinase activity is essential for osmotic induction of mRNAs for HSP70 and transporter for organic solute betaine in Madin-Darby canine kidney cells. J Biol Chem 1998. 273:1832-1837.
    View this article via: PubMed CrossRef Google Scholar
36. Whorton, A, et al. Prostaglandins and renin release. I. Stimulation of renin release from rabbit renal cortical slices by PGI₂. Prostaglandins 1977. 14:1095-1104.
    View this article via: PubMed CrossRef Google Scholar
37. Jensen, BL, Schmid, C, Kurtz, A. Prostaglandins stimulate renin secretion and renin mRNA in mouse renal juxtaglomerular cells. Am J Physiol 1996. 271:F659-F669.
    View this article via: PubMed Google Scholar
38. Okuda, T, Naruse, M, Kurokawa, K. Mesangial cell function and chloride ions. Kidney Int 1991. 39(Suppl. 32):S65-S67.
39. Tsukahara, H, Krivenko, Y, Moore, LC, Goligorsky, MS. Decrease in ambient [Cl-] stimulates nitric oxide release from cultured rat mesangial cells. Am J Physiol 1994. 267:F190-F195.
    View this article via: PubMed Google Scholar
40. Kummer, JL, Rao, PK, Heidenreich, KA. Apoptosis induced by withdrawal of trophic factors is mediated by p38 mitogen-activated protein kinase. J Biol Chem 1997. 272:20490-20494.
    View this article via: PubMed CrossRef Google Scholar
41. Ito, T, et al. p38 MAP kinase is required for vasopressin-stimulated HSP27 induction in aortic smooth muscle cells. Hypertension 2000. 35:673-678.
    View this article via: PubMed Google Scholar
42. Alessi, DR, Cuenda, A, Cohen, P, Dudley, DT, Saltiel, AR. PD 098059 is a specific inhibitor of the activation of mitogen-activated protein kinase kinase in vitro and in vivo. J Biol Chem 1995. 270:27489-27494.
    View this article via: PubMed CrossRef Google Scholar
43. Lagaud, GJ, Lam, E, Lui, A, van Breemen, C, Laher, I. Nonspecific inhibition of myogenic tone by PD98059, a MEK1 inhibitor, in rat middle cerebral arteries. Biochem Biophys Res Commun 1999. 257:523-527.
    View this article via: PubMed CrossRef Google Scholar
44. Schaeffer, HJ, Weber, MJ. Mitogen-activated protein kinases: specific messages from ubiquitous messengers. Mol Cell Biol 1999. 19:2435-2444.
    View this article via: PubMed Google Scholar
45. Widmann, C, Gibson, S, Jarpe, MB, Johnson, GL. Mitogen-activated protein kinase: conservation of a three-kinase module from yeast to human. Physiol Rev 1999. 79:143-180.
    View this article via: PubMed Google Scholar
46. Ichijo, H. From receptors to stress-activated MAP kinases. Oncogene 1999. 18:6087-6093.
    View this article via: PubMed CrossRef Google Scholar
47. English, J, et al. New insights into the control of MAP kinase pathways. Exp Cell Res 1999. 253:255-270.
    View this article via: PubMed CrossRef Google Scholar
48. Roger, F, Martin, PY, Rousselot, M, Favre, H, Feraille, E. Cell shrinkage triggers the activation of mitogen-activated protein kinases by hypertonicity in the rat kidney medullary thick ascending limb of the Henle’s loop. Requirement of p38 kinase for the regulatory volume increase response. J Biol Chem 1999. 274:34103-34110.
    View this article via: PubMed CrossRef Google Scholar
49. Watts (III), BA, Di Mari, JF, Davis, RJ, Good, DW. Hypertonicity activates MAP kinases and inhibits HCO-3 absorption via distinct pathways in thick ascending limb. Am J Physiol 1998. 275:F478-F486.
    View this article via: PubMed Google Scholar
50. LaPointe, MC, Isenovic, E. Interleukin-1beta regulation of inducible nitric oxide synthase and cyclooxygenase-2 involves the p42/44 and p38 MAPK signaling pathways in cardiac myocytes. Hypertension 1999. 33:276-282.
    View this article via: PubMed Google Scholar
51. Subbaramaiah, K, Chung, WJ, Dannenberg, AJ. Ceramide regulates the transcription of cyclooxygenase-2. Evidence for involvement of extracellular signal-regulated kinase/c-Jun N-terminal kinase and p38 mitogen-activated protein kinase pathways. J Biol Chem 1998. 273:32943-32949.
    View this article via: PubMed CrossRef Google Scholar
52. Guan, Z, Buckman, SY, Miller, BW, Springer, LD, Morrison, AR. Interleukin-1beta-induced cyclooxygenase-2 expression requires activation of both c-Jun NH2-terminal kinase and p38 MAPK signal pathways in rat renal mesangial cells. J Biol Chem 1998. 273:28670-28676.
    View this article via: PubMed CrossRef Google Scholar
53. Xie, W, Herschman, HR. Transcriptional regulation of prostaglandin synthase 2 gene expression by platelet-derived growth factor and serum. J Biol Chem 1996. 271:31742-31748.
    View this article via: PubMed CrossRef Google Scholar
54. Shalom-Barak, T, Quach, J, Lotz, M. Interleukin-17-induced gene expression in articular chondrocytes is associated with activation of mitogen-activated protein kinases and NF-kappaB. J Biol Chem 1998. 273:27467-27473.
    View this article via: PubMed CrossRef Google Scholar
55. Bartlett, SR, Sawdy, R, Mann, GE. Induction of cyclooxygenase-2 expression in human myometrial smooth muscle cells by interleukin-1beta: involvement of p38 mitogen-activated protein kinase. J Physiol (Lond) 1999. 520:399-406.
    View this article via: PubMed CrossRef Google Scholar
56. Ridley, SH, et al. A p38 MAP kinase inhibitor regulates stability of interleukin-1-induced cyclooxygenase-2 mRNA. FEBS Lett 1998. 439:75-80.
    View this article via: PubMed CrossRef Google Scholar
57. Wadleigh, DJ, Reddy, ST, Kopp, E, Ghosh, S, Herschman, HR. Transcriptional activation of the cyclooxygenase-2 gene in endotoxin-treated RAW 264.7 macrophages. J Biol Chem 2000. 275:6259-6266.
    View this article via: PubMed CrossRef Google Scholar
58. Caivano, M, Cohen, P. Role of mitogen-activated protein kinase cascades in mediating lipopolysaccharide-stimulated induction of cyclooxygenase-2 and IL-1 beta in RAW264 macrophages. J Immunol 2000. 164:3018-3025.
    View this article via: PubMed Google Scholar
59. Pizzonia, JH, et al. Immunomagnetic separation, primary culture, and characterization of cortical thick ascending limb plus distal convoluted tubule cells from mouse kidney. In Vitro Cell Dev Biol 1991. 27A:409-416.
    View this article via: PubMed Google Scholar
60. Wilcox, CS, et al. Nitric oxide synthase in macula densa regulates glomerular capillary pressure. Proc Natl Acad Sci USA 1992. 89:11993-11997.
    View this article via: PubMed CrossRef Google Scholar
61. Vio, CP, Cespedes, C, Gallardo, P, Masferrer, JL. Renal identification of cyclooxygenase-2 in a subset of thick ascending limb cells. Hypertension 1997. 30:687-692.
    View this article via: PubMed Google Scholar
62. Bosse, HM, Bohm, R, Resch, S, Bachmann, S. Parallel regulation of constitutive NO synthase and renin at JGA of rat kidney under various stimuli. Am J Physiol 1995. 269:F793-F805.
    View this article via: PubMed Google Scholar
63. Kihara, M, et al. Expression of neuronal type nitric oxide synthase and renin in the juxtaglomerular apparatus of angiotensin type-1a receptor gene-knockout mice. Kidney Int 1998. 53:1585-1593.
    View this article via: PubMed CrossRef Google Scholar