Review
Abstract
Peptidyl arginine deiminases (PADs) catalyze the conversion of arginine residues into peptidyl citrulline, a posttranslational modification known as protein citrullination (or arginine deimination). This process alters the charge of proteins from positive to neutral, thereby affecting their folding, stability, conformation, and function. PAD2 and PAD4 can translocate into the nucleus and citrullinate both cytoplasmic and nuclear proteins. In this Review, we focus on PAD2- and PAD4-mediated citrullination in immune cell subsets within the tumor microenvironment. We discuss how citrullination regulates immune cell function and tumor immunity and explore the potential of targeting citrullination as a strategy for cancer immunotherapy.
Authors
Michael R. Pitter, Weiping Zou
Abstract
The increasing recognition of a new category of encephalitides that occur in association with antibodies against neuronal surface proteins has prompted the use of terms like “autoimmune psychosis” and “autoimmune psychiatric disorders.” However, although psychosis and other psychiatric symptoms can occur in autoimmune encephalitides and systemic autoimmune diseases, evidence for a distinct psychiatric entity beyond these conditions is lacking. A particularly defining condition is anti-NMDA receptor encephalitis, which has been central to promoting concepts such as autoimmune psychosis and autoimmune psychiatric disorders. While anti-NMDA receptor encephalitis can resemble primary psychiatric conditions, certain clinical features often suggest the specific diagnosis. This Review traces the development of the autoimmune psychosis concept and examines the implications of framing it as a separate entity. We discuss leading theories of psychosis and the convergence of the NMDA receptor hypofunction/glutamate hypothesis with anti-NMDA receptor encephalitis mechanisms. The interest generated by such disorders has driven uncontrolled antibody testing in psychiatric populations, often neglecting pretest probability and favoring prevalence over diagnostic specificity. Finally, we highlight the main limitations of current approaches and propose directions for future research.
Authors
José Maria Cabrera-Maqueda, Jesús Planagumà, Mar Guasp, Josep Dalmau
Abstract
Chronic organ disease is often complicated by fibrosis, the excessive accumulation of extracellular matrix, as a consequence of dysfunctional wound healing responses. Fibrosis progressively distorts tissue architecture and eventually leads to loss of organ function, accounting for up to 45% of deaths in developed countries. Moreover, fibrosis is a major risk factor for tumor development. The few approved therapies aimed at preventing or resolving fibrosis show limited efficacy and safety. One reason for the lack of efficient antifibrotic therapies is the fact that the cell circuits driving the disease biology are still only partially understood. The circadian clock is known to regulate the physiological functions of critical organs, including the liver, kidneys, and lungs. Several experimental and clinical studies have established that circadian disruption plays an important role in the development of chronic diseases across organs involving fibrosis. These include metabolic dysfunction–associated steatotic liver disease, chronic kidney disease, and chronic obstructive pulmonary disease. Here, we provide an overview of the circadian mechanisms that play critical roles in mediating physiological functions in the liver, kidneys, and lungs and whose deregulations could predispose toward development of chronic disease of these organs, leading to fibrosis. We also highlight the possible opportunities of chronotherapy for chronic diseases and discuss future perspectives.
Authors
Atish Mukherji, Pierre-Louis Tharaux, David W. Ray, Thomas F. Baumert
Abstract
Rheumatoid arthritis (RA) has a preclinical period of 5–10 years preceding the appearance of joint pain and swelling characteristic of clinical RA. Preclinical RA has been characterized by circulating IgA and IgG classes of autoantibodies targeting citrullinated protein antigens (ACPAs) that are highly specific for future clinical RA, circulating IgA plasmablasts, and autoantibody production at mucosal sites, all of which point toward mucosal tissues as the origin of immune dysregulation. In individuals at risk for developing and with established RA, oral and gut microbial shifts correlate with immune activation. Specific bacterial taxa such as Segatella copri, Subdoligranulum didolesgii, Eggerthella lenta, and Streptococcal species have been shown to contribute to the development and/or perpetuation of RA through mechanisms that include molecular mimicry, antigen citrullination, and disruption of mucosal immunity. Furthermore, microbial metabolites, including short-chain fatty acids, bile acids, and tryptophan derivatives, regulate immune homeostasis and offer potential therapeutic avenues. The gut microbiome also influences therapeutic responses by modulating conventional disease-modifying antirheumatic drugs. This Review synthesizes current knowledge on the bacterial microbiome’s role in RA pathogenesis and treatment responses, highlighting microbiome-targeted interventions as potential strategies for disease prevention and management.
Authors
Jing Li, Kristine A. Kuhn
Abstract
Trained immunity (TRIM) is a form of long-lasting functional reprogramming of innate immune cells and their progenitors that enhances responsiveness to subsequent stimuli. Although first characterized in myeloid cells, TRIM was recently extended to nonmyeloid cell types, including endothelial and glial cells, which also exhibit stimulus-driven, memory-like behavior. While initially recognized as a protective mechanism, particularly in the context of vaccines and acute infections, TRIM can also become maladaptive, promoting chronic inflammation, immune dysfunction, and disease. This Review focuses on virus-induced TRIM while also addressing microbial, metabolic, and endogenous inducers. We examine key ligands and receptors that initiate TRIM and dissect the associated signaling and epigenetic pathways. Importantly, we argue that maladaptive TRIM arises not from a specific ligand, receptor, or molecular event, but from contextual factors such as stimulus persistence, dose, tissue microenvironment, and preexisting inflammation. The nature of the secondary challenge also shapes whether a trained response is adaptive or maladaptive. We further discuss TRIM induction in the bone marrow, involvement of both myeloid and nonmyeloid cells, and the role of lipid rafts in sustaining TRIM. We review maladaptive TRIM’s potential contribution to systemic diseases, such as atherosclerosis, diabetes, sepsis, cancer, and autoimmunity, along with its influence on viral vaccine responses. Finally, we outline potential strategies to redirect maladaptive TRIM and propose key outstanding questions for future research.
Authors
Dmitri Sviridov, Mihai G. Netea, Michael I. Bukrinsky
Abstract
Air pollution comprises a complex mixture of gaseous and particulate components. Particulate matter (PM) air pollution is associated with 4.7 million premature deaths per year. Among modifiable risk factors, air pollution exposure contributes to 8% of disability adjusted life years and ranks above factors such as high blood pressure, smoking, and high fasting plasma glucose. As the site of entry, exposure to PM air pollution causes respiratory symptoms and is a significant cause of respiratory morbidity and mortality. In this Review, we discuss the studies that link air pollution exposure with respiratory diseases. We review the epidemiological evidence linking PM exposure and lung diseases including asthma, chronic obstructive pulmonary disease, pulmonary fibrosis, pneumonia, acute respiratory distress syndrome, and lung cancer. We also provide an overview of current knowledge about the mechanisms by which PM exerts its biological effects leading to adverse health effects in the respiratory system.
Authors
Robert B. Hamanaka, Gökhan M. Mutlu
Abstract
The immune system must identify genuine threats and avoid reacting to harmless microbes because immune responses, while critical for organismal survival, can cause severe damage and use substantial energy resources. Models for immune response initiation have mostly focused on the direct sensing of microorganisms through pattern recognition receptors. Here, we summarize key features of the leading models of immune response initiation and identify issues they fail to solve individually, including how the immune system distinguishes between pathogens and commensals. We hypothesize and argue that surveillance of disruption to organismal homeostasis and core cellular activities is central to detecting and resolving relevant threats effectively, including infection. We propose that hosts use pattern recognition receptors to identify microorganisms and use sensing of homeostasis disruption to assess the level of threat they pose. We predict that both types of information can be integrated through molecular coincidence detectors (such as inflammasomes or others not yet discovered) and used to determine whether to initiate an immune response, its quality, and its magnitude. This conceptual framework may guide the identification of novel targets and therapeutic strategies to improve the progression and outcome of infection, cancer, autoimmunity, and chronic conditions in which inflammation plays a critical role.
Authors
Katharina Willmann, Luis F. Moita
Abstract
A central challenge in cancer therapy is the effective delivery of anticancer treatments while minimizing adverse effects on patient health. The potential dual impact of therapy is clearly illustrated in cancer-associated cachexia, a multifactorial syndrome characterized by involuntary weight loss, systemic inflammation, metabolic dysregulation, and behavioral alterations such as anorexia and apathy. While cachexia research often focuses on tumor-driven mechanisms, the literature indicates that cancer therapies themselves, particularly chemotherapies and targeted treatments, can initiate or exacerbate the biological pathways driving this syndrome. Here, we explore how therapeutic interventions intersect with the pathophysiology of cachexia, focusing on key organ systems including muscle, adipose tissue, liver, heart, and brain. We highlight examples such as therapy-induced upregulation of IL-6 and growth-differentiation factor 15, both contributing to reduced nutrient intake and a negative energy balance via brain-specific mechanisms. At the level of nutrient release and organ atrophy, chemotherapies also converge with cancer progression, for example, activating NF-κB in muscle and PKA/CREB signaling in adipose tissue. By examining how treatment timing and modality align with the natural trajectory of cancer cachexia, we underscore the importance of incorporating physiological endpoints alongside tumor-centric metrics in clinical trials. Such integrative approaches may better capture therapeutic efficacy while preserving patient well-being.
Authors
Tuba Mansoor Thakir, Alice R. Wang, Amanda R. Decker-Farrell, Miriam Ferrer, Rohini N. Guin, Sam Kleeman, Llewelyn Levett, Xiang Zhao, Tobias Janowitz
Abstract
As the use of molecular profiling of tumors expands, cancer diagnosis, prognosis, and treatment planning increasingly rely on the information it provides. Although primarily designed to detect somatic variants, next-generation sequencing (NGS) tumor-based profiling also identifies germline DNA alterations, necessitating careful clinical interpretation of the data. Traditionally, germline risk testing has depended on prioritizing individuals based on physical exam findings consistent with known hereditary cancer syndromes, tumor-specific features, age at diagnosis, personal history, and family history. As NGS-based molecular profiling is used increasingly to diagnose, prognosticate, and follow cancer progression, DNA variants that are likely to be of germline origin are identified with increased frequency. Because pathogenic/likely pathogenic germline variants are critical biomarkers for risk stratification and treatment planning, consensus guidelines are expanding to recommend comprehensive germline testing for more cancer patients. This Review highlights the nuances of identifying DNA variants of potential germline origin incidentally at the time of NGS-based molecular profiling and emphasizes key differences between comprehensive germline versus tumor-based platforms, sample types, and analytical methodologies. In the growing era of precision oncology, clinicians should be adept at navigating these distinctions to optimize testing strategies and leverage insights regarding germline cancer risk surveillance and management for all people with cancer.
Authors
Diana Jaber, Jessica Zhang, Lucy A. Godley
Abstract
Endometriosis is an estrogen-dependent chronic inflammatory syndrome characterized by viable endometrial tissue outside the uterine cavity and associated with pain and infertility. Endometriosis, as tissue or a pathological process, is dynamic in that its establishment and progression require repeated episodes of retrograde travel of shed endometrial tissue, which implants in the lower abdominal cavity following ovulatory cycles and survives. Estrogen-rich follicular fluid released onto peritoneal surfaces during ovulation may also support endometriotic implants. DNA evidence indicates that endometriosis originates from eutopic endometrial tissue, which may reach the abdominal cavity in a retrograde manner primarily via the uterine tubes. Unlike uterine bleeding associated with non-ovulatory circumstances, retrograde menstruation following an ovulation maximizes shedding of epithelial cells localized to deep invaginations of the basalis portion of the endometrium, which likely carry somatic cancer-driver mutations such as KRAS. The attached endometrial stromal cells are mostly mutation free but display epigenetic defects including overexpression of aromatase and estrogen receptor-β and downregulation of progesterone receptor, causing estrogen excess and progesterone resistance. These tissue clones may form implants in involuting ovarian corpus luteum cysts and peritoneal surfaces and induce tissue remodeling and fibrosis, manifested as deep-infiltrating endometriosis. The first-line treatment for chronic pelvic pain associated with endometriosis is suppression of ovulation, with the goal of relieving pain. Infertility is often managed using in vitro fertilization, which improves the embryo quality and alters endometrial development.
Authors
Serdar E. Bulun
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