Type I regulatory T (Tr1) cells are a population of regulatory CD4+ T cells implicated in the suppression of pathological immune responses across multiple diseases, but a unifying transcriptional signature of Tr1 identity across disease contexts has not been characterized. In this issue of the JCI, Edward, Ng, and colleagues identified a conserved transcriptional signature that distinguished Tr1 (IL-10+IFN-γ+) from Th1 (IL-10–IFN-γ+) cells in human and mouse malaria. This signature implicated genes encoding inhibitory receptors — including CTLA-4 and LAG-3 — and transcription factors — including cMAF. The authors identified coinhibitory receptor expression that distinguished Tr1 cells from other CD4+ T cell subsets. Furthermore, cMAF — and, to a lesser extent, BLIMP-1 — promoted IL-10 production in human CD4+ T cells. BLIMP-1 also played a role in supporting the expression of inhibitory receptors. These findings describe a few key features that seem to be conserved by Tr1 cells across multiple species, disease contexts, and marker definitions.
Jason Nideffer, Prasanna Jagannathan
Viperin, an IFN-regulated gene product, is known to inhibit fatty acid β-oxidation in the mitochondria, which enhances glycolysis and lipogenesis during viral infections. Yet, its role in altering the phenotype of cancer cells has not been established. In this issue of the JCI, Choi, Kim, and co-authors report on a role of viperin in regulating metabolic alterations in cancer cells. The authors showed a correlation between clinical outcomes and viperin expression levels in multiple cancer tissues and proposed that viperin expression was upregulated in the tumor microenvironment via the JAK/STAT and PI3K/AKT/mTOR/HIF-1α pathways. Functionally, viperin increased lipogenesis and glycolysis in cancer cells by inhibiting fatty acid β-oxidation. Viperin expression also enhanced cancer stem cell properties, ultimately promoting tumor initiation in murine models. This study proposes a protumorigenic role for viperin and identifies HIF-1α as a transcription factor that increases viperin expression under serum starvation and hypoxia.
Alyssa G. Weinstein, Inês Godet, Daniele M. Gilkes
Atherosclerosis contributes to the majority of deaths related to cardiovascular disease (CVD). Recently, the nonspecific inflammatory biomarker soluble urokinase plasminogen activator receptor (suPAR) has shown prognostic value in patients with CVD; however, it remains unclear whether suPAR participates in the disease process. In this issue of the JCI, Hindy and colleagues report on their evaluation of a multi-ethnic cohort of over 5,000 participants without known CVD. High suPAR levels correlated with incident CVD and atherosclerosis. Genetic analysis revealed two variants associated with the suPAR-encoding gene (PLAUR) with higher plasma suPAR levels. Notably, a mouse model with high suPAR levels possessed aortic tissue with a proinflammatory phenotype, including monocytes with enhanced chemotaxis similar to that seen in atherogenesis. These findings suggest a causal relationship between suPAR and coronary artery calcification and have clinical implications that extend to inflammatory disorders beyond CVD.
Traci T. Goodchild, Zhen Li, David J. Lefer
NK cells are an important subset of innate immune effectors with antiviral activity. However, NK cell development and immune responses in different tissues during acute and chronic HIV infection in vivo have been difficult to study due to the impaired development and function of NK cells in conventional humanized mouse models. In this issue of the JCI, Sangur et al. report on a transgenic MISTRG-6-15 mouse model with human IL-6 and IL-15 knocked into the previously constructed MISTRG mice. The predecessor model was deficient in Rag2 and γ chain (γc) with knock-in expression of human M-CSF, IL-3, GM-CSF, and TPO, and transgenic expression of human SIRPα. The researchers studied tissue–specific NK cell immune responses during HIV infection and clearly show that the endogenous human NK cells in the humanized mouse model suppressed HIV-1 replication in vivo. These findings provide insight into harnessing the innate immune response for clinical antiviral therapies.
Jocelyn T. Kim, Jerome A. Zack
Opioid-induced hyperalgesia (OIH) is a state of paradoxically enhanced pain transmission, termed nociceptive sensitization, described to occur in both humans and animals after repeated administration of opioid drugs, including rapidly acting remifentanil. However, molecular mechanisms of OIH remain understudied. In this issue of the JCI, Yan Jin and colleagues provided strong evidence that hyperexcitable thalamocortical networks drive remifentanil-induced hyperalgesia in a rodent model of postsurgical pain. Furthermore, the authors specifically identified an important role of the CaV3.1 isoform of low-voltage-activated or T-type calcium channels (T-channels) in this process. Further experiments are needed to determine whether thalamic T channels could serve as targets for the treatment of OIH.
Slobodan M. Todorovic
Fibroblastic reticular cells (FRCs) maintain the architecture of secondary lymphoid organs, which optimize interactions between antigen-presenting dendritic cells and reactive naive T cells. In this issue of the JCI, Zhao, Jung, and colleagues investigated CD4+FoxP3+ regulatory T cell development and long-term heart allograft survival in recipients treated with peritransplant costimulatory blockade to inhibit CD40/CD40 ligand (CD40L) signaling. Treatment with an anti-CD40L monoclonal antibody (mAb) increased the lymph node (LN) population of Madcam1+ FRCs and altered their transcription profile to express immunoregulatory mediators. Administration of nanoparticles, containing the anti-CD40L mAb and a targeting antibody against high endothelial venules, delivered the treatment into LNs of allograft recipients. Direct LN delivery of the costimulatory blockade allowed decreased dosing and increased the efficacy in extending graft survival. The results provide insights into mechanisms by which FRCs can promote donor-reactive tolerance, and establish a strategy for administering costimulation-blocking reagents that circumvent systemic effects and improve allograft outcomes.
Robert L. Fairchild
Muscle fibers express particular isoforms of contractile proteins, depending on the fiber’s function and the organism’s developmental stage. In the adult, after a muscle injury, newly generated fibers transition through embryonic and neonatal myosins, prior to selecting their distinctive adult myosin isoform. In this issue of the JCI, Wang et al. discover a checkpoint that regulates the neonatal-to-adult myosin isoform transition. They found that HIF-1α regulated this checkpoint, with elevated HIF-1α levels blocking progression, while HIF-1α knockout accelerated the transition. They further related these findings to centronuclear myopathy, a disease in which HIF-1α is similarly elevated and neonatal myosin expression is maintained. These findings highlight a maturation checkpoint that impacts the skeletal muscle regeneration following ischemic injury, providing a pharmacologically accessible pathway in injury and diseases such as centronuclear myopathy.
Rahagir Salekeen, Michael Kyba
Androgen deprivation therapy (ADT) is the longstanding treatment for advanced prostate cancer (PC) because androgen receptor (AR) is the key therapeutic vulnerability for this disease. Bipolar androgen therapy (BAT) — the rapid cycling of supraphysiologic androgen (SPA) and low serum testosterone levels — is an alternative concept, but not all patients respond and acquired resistance can occur. In this issue of the JCI, Sena et al. developed a gene signature indicative of high AR activity to predict patient response to BAT, including a decline in both serum prostate-specific antigen (PSA) and tumor volume. Preclinical models showed that AR-mediated suppression of MYC, known to drive PC, was associated with decreased cell growth following SPA treatment. Because BAT eventually leads to resistance, the authors tested cycling between SPA and AR antagonism in a patient-derived xenograft and observed a delay in tumor growth. These findings represent a major step toward the informed use of BAT for advanced PC.
Nahuel Peinetti, Marijo Bilusic, Kerry L. Burnstein
Myeloid-derived suppressor cells (MDSCs) hinder antitumor immunity in multiple cancer types. While brequinar (BRQ), an inhibitor of dihydroorotate dehydrogenase, shows cytotoxicity in hematological malignancy, it has not yet been adapted to attenuate MDSCs by augmenting bone marrow progenitors in breast cancer. In this issue of the JCI, Colligan et al. demonstrate that BRQ restored terminal differentiation of MDSCs. Using in vivo models of immunotherapy-resistant breast cancer, the authors uncovered a mechanism by which BRQ promoted myeloid cell differentiation by limiting their suppressive function and enhancing the efficacy of immune checkpoint blockade therapy. The findings offer insight into the biogenesis of MDSCs, provide an alternative avenue for cancers that remain unresponsive to conventional therapies, and may be extended to future translational studies in patients.
Natalie K. Horvat, Gregory B. Lesinski
Understanding the cellular mechanisms underlying chronic kidney disease (CKD) progression is required to develop effective therapeutic approaches. In this issue of the JCI, Taguchi, Elias, et al. explore the relationship between cyclin G1 (CG1), an atypical cyclin that induces G2/M proximal tubule cell cycle arrest, and epithelial dedifferentiation during fibrogenesis. While CG1-knockout mice were protected from fibrosis and had reduced G2/M arrest, protection was unexpectedly independent of induction of G2/M arrest. Rather, CG1 drove fibrosis by regulating maladaptive dedifferentiation in a CDK5-dependent mechanism. These findings highlight the importance of maladaptive epithelial dedifferentiation in kidney fibrogenesis and identify CG1/CDK5 signaling as a therapeutic target in CKD progression.
Benjamin D. Humphreys
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