ANTXR1 deficiency promotes fibroblast senescence: implications for GAPO syndrome as a progeroid disorder.

ANTXR1 is one of two cell surface receptors mediating the uptake of the anthrax toxin into cells. Despite substantial research on its role in anthrax poisoning and a proposed function as a collagen receptor, ANTXR1's physiological functions remain largely undefined. Pathogenic variants in ANTXR1 lead to the rare GAPO syndrome, named for its four primary features: Growth retardation, Alopecia, Pseudoanodontia, and Optic atrophy. The disease is also associated with a complex range of other phenotypes impacting the cardiovascular, skeletal, pulmonary and nervous systems. Aberrant accumulation of extracellular matrix components and fibrosis are considered to be crucial components in the pathogenesis of GAPO syndrome, contributing to the shortened life expectancy of affected individuals. Nonetheless, the specific mechanisms connecting ANTXR1 deficiency to the clinical manifestations of GAPO syndrome are largely unexplored. In this study, we present evidence that ANTXR1 deficiency initiates a senescent phenotype in human fibroblasts, correlating with defects in nuclear architecture and actin dynamics. We provide novel insights into ANTXR1's physiological functions and propose GAPO syndrome to be reconsidered as a progeroid disorder highlighting an unexpected role for an integrin-like extracellular matrix receptor in human aging.

NLRP6 controls pulmonary inflammation from cigarette smoke in a gut microbiota-dependent manner.

Chronic obstructive pulmonary disease (COPD) is a major health issue primarily caused by cigarette smoke (CS) and characterized by breathlessness and repeated airway inflammation. NLRP6 is a cytosolic innate receptor controlling intestinal inflammation and orchestrating the colonic host-microbial interface. However, its roles in the lungs remain largely unexplored. Using CS exposure models, our data show that airway inflammation is strongly impaired in Nlrp6-deficient mice with drastically fewer recruited neutrophils, a key cell subset in inflammation and COPD. We found that NLRP6 expression in lung epithelial cells is important to control airway and lung tissue inflammation in an inflammasome-dependent manner. Since gut-derived metabolites regulate NLRP6 inflammasome activation in intestinal epithelial cells, we investigated the link between NLRP6, CS-driven lung inflammation, and gut microbiota composition. We report that acute CS exposure alters gut microbiota in both wild-type (WT) and Nlrp6-deficient mice and that antibiotic treatment decreases CS-induced lung inflammation. In addition, gut microbiota transfer from dysbiotic Nlrp6-deficient mice to WT mice decreased airway lung inflammation in WT mice, highlighting an NLRP6-dependent gut-to-lung axis controlling pulmonary inflammation.

Metastatic recurrence in colorectal cancer arises from residual EMP1+ cells.

Around 30-40% of patients with colorectal cancer (CRC) undergoing curative resection of the primary tumour will develop metastases in the subsequent years1. Therapies to prevent disease relapse remain an unmet medical need. Here we uncover the identity and features of the residual tumour cells responsible for CRC relapse. An analysis of single-cell transcriptomes of samples from patients with CRC revealed that the majority of genes associated with a poor prognosis are expressed by a unique tumour cell population that we named high-relapse cells (HRCs). We established a human-like mouse model of microsatellite-stable CRC that undergoes metastatic relapse after surgical resection of the primary tumour. Residual HRCs occult in mouse livers after primary CRC surgery gave rise to multiple cell types over time, including LGR5+ stem-like tumour cells2-4, and caused overt metastatic disease. Using Emp1 (encoding epithelial membrane protein 1) as a marker gene for HRCs, we tracked and selectively eliminated this cell population. Genetic ablation of EMP1high cells prevented metastatic recurrence and mice remained disease-free after surgery. We also found that HRC-rich micrometastases were infiltrated with T cells, yet became progressively immune-excluded during outgrowth. Treatment with neoadjuvant immunotherapy eliminated residual metastatic cells and prevented mice from relapsing after surgery. Together, our findings reveal the cell-state dynamics of residual disease in CRC and anticipate that therapies targeting HRCs may help to avoid metastatic relapse.

Influenza A Virus Agnostic Receptor Tropism Revealed Using a Novel Biological System with Terminal Sialic Acid Knockout Cells.

Avian or human influenza A viruses bind preferentially to avian- or human-type sialic acid receptors, respectively, indicating that receptor tropism is an important factor for determining the viral host range. However, there are currently no reliable methods for analyzing receptor tropism biologically under physiological conditions. In this study, we established a novel system using MDCK cells with avian- or human-type sialic acid receptors and with both sialic acid receptors knocked out (KO). When we examined the replication of human and avian influenza viruses in these KO cells, we observed unique viral receptor tropism that could not be detected using a conventional solid-phase sialylglycan binding assay, which directly assesses physical binding between the virus and sialic acids. Furthermore, we serially passaged an engineered avian-derived H4N5 influenza virus, whose PB2 gene was deleted, in avian-type receptor KO cells stably expressing PB2 to select a mutant with enhanced replication in KO cells; however, its binding to human-type sialylglycan was undetectable using the solid-phase binding assay. These data indicate that a panel of sialic acid receptor KO cells could be a useful tool for determining the biological receptor tropism of influenza A viruses. Moreover, the PB2KO virus experimental system could help to safely and efficiently identify the mutations required for avian influenza viruses to adapt to human cells that could trigger a new influenza pandemic. IMPORTANCE The acquisition of mutations that allow avian influenza A virus hemagglutinins to recognize human-type receptors is mandatory for the transmission of avian viruses to humans, which could lead to a pandemic. In this study, we established a novel system using a set of genetically engineered MDCK cells with knocked out sialic acid receptors to biologically evaluate the receptor tropism for influenza A viruses. Using this system, we observed unique receptor tropism in several virus strains that was undetectable using conventional solid-phase binding assays that measure physical binding between the virus and artificially synthesized sialylglycans. This study contributes to elucidation of the relationship between the physical binding of virus and receptor and viral infectivity. Furthermore, the system using sialic acid knockout cells could provide a useful tool to explore the sialic acid-independent entry mechanism. In addition, our system could be safely used to identify mutations that could acquire human-type receptor tropism.

NLRP6 Inflammasome Modulates Disease Progression in a Chronic-Plus-Binge Mouse Model of Alcoholic Liver Disease.

A considerable percentage of the population is affected by alcoholic liver disease (ALD). It is characterized by inflammatory signals from the liver and other organs, such as the intestine. The NLR family pyrin domain containing 6 (NLRP6) inflammasome complex is one of the most important inflammatory mediators. The aim of this study was to evaluate a novel mouse model for ALD characterized by 8-week chronic-plus-binge ethanol administration and to investigate the role of NLRP6 inflammasome for intestinal homeostasis and ALD progression using Nlrp6-/- mice. We showed that chronic-plus-binge ethanol administration triggers hepatic steatosis, injury, and neutrophil infiltration. Furthermore, we discovered significant changes of intestinal microbial communities, including increased relative abundances of bacteria within the phyla Bacteroidota and Campilobacterota, as well as reduced Firmicutes. In this ALD model, inhibiting NLRP6 signaling had no effect on liver steatosis or damage, but had a minor impact on intestinal homeostasis via affecting intestinal epithelium function and gut microbiota. Surprisingly, Nlrp6 loss resulted in significantly decreased hepatic immune cell infiltration. As a result, our novel mouse model encompasses several aspects of human ALD, such as intestinal dysbiosis. Interfering with NLRP6 inflammasome activity reduced hepatic immune cell recruitment, indicating a disease-aggravating role of NLRP6 during ALD.

CD177 modulates the function and homeostasis of tumor-infiltrating regulatory T cells.

Regulatory T (Treg) cells are one of the major immunosuppressive cell types in cancer and a potential target for immunotherapy, but targeting tumor-infiltrating (TI) Treg cells has been challenging. Here, using single-cell RNA sequencing of immune cells from renal clear cell carcinoma (ccRCC) patients, we identify two distinct transcriptional fates for TI Treg cells, Fate-1 and Fate-2. The Fate-1 signature is associated with a poorer prognosis in ccRCC and several other solid cancers. CD177, a cell surface protein normally expressed on neutrophil, is specifically expressed on Fate-1 TI Treg cells in several solid cancer types, but not on other TI or peripheral Treg cells. Mechanistically, blocking CD177 reduces the suppressive activity of Treg cells in vitro, while Treg-specific deletion of Cd177 leads to decreased tumor growth and reduced TI Treg frequency in mice. Our results thus uncover a functional CD177+ TI Treg population that may serve as a target for TI Treg-specific immunotherapy.

Siglec-H-Deficient Mice Show Enhanced Type I IFN Responses, but Do Not Develop Autoimmunity After Influenza or LCMV Infections.

Siglec-H is a DAP12-associated receptor on plasmacytoid dendritic cells (pDCs) and microglia. Siglec-H inhibits TLR9-induced IFN-α production by pDCs. Previously, it was found that Siglec-H-deficient mice develop a lupus-like severe autoimmune disease after persistent murine cytomegalovirus (mCMV) infection. This was due to enhanced type I interferon responses, including IFN-α. Here we examined, whether other virus infections can also induce autoimmunity in Siglec-H-deficient mice. To this end we infected Siglec-H-deficient mice with influenza virus or with Lymphocytic Choriomeningitis virus (LCMV) clone 13. With both types of viruses we did not observe induction of autoimmune disease in Siglec-H-deficient mice. This can be explained by the fact that both types of viruses are ssRNA viruses that engage TLR7, rather than TLR9. Also, Influenza causes an acute infection that is rapidly cleared and the chronicity of LCMV clone 13 may not be sufficient and may rather suppress pDC functions. Siglec-H inhibited exclusively TLR-9 driven type I interferon responses, but did not affect type II or type III interferon production by pDCs. Siglec-H-deficient pDCs showed impaired Hck expression, which is a Src-family kinase expressed in myeloid cells, and downmodulation of the chemokine receptor CCR9, that has important functions for pDCs. Accordingly, Siglec-H-deficient pDCs showed impaired migration towards the CCR9 ligand CCL25. Furthermore, autoimmune-related genes such as Klk1 and DNase1l3 are downregulated in Siglec-H-deficient pDCs as well. From these findings we conclude that Siglec-H controls TLR-9-dependent, but not TLR-7 dependent inflammatory responses after virus infections and regulates chemokine responsiveness of pDCs.

PLXNA2 knockdown promotes M2 microglia polarization through mTOR/STAT3 signaling to improve functional recovery in rats after cerebral ischemia/reperfusion injury.

Ischemic stroke is an acute cerebrovascular disease characterized by high mortality, morbidity and disability rates. Ischemia/reperfusion is a critical pathophysiological basis of motor and cognitive dysfunction caused by ischemic stroke. Microglia, innate immune cells of the central nervous system, mediate the neuroinflammatory response to ischemia/reperfusion. PlexinA2 (PLXNA2) plays an important role in the regulation of neuronal axon guidance, the immune response and angiogenesis. However, it is not clear whether PLXNA2 regulates microglia polarization in ischemic stroke or the underlying mechanism. In the present study, we investigated the role of PLXNA2 in rats with middle cerebral artery occlusion/reperfusion (MCAO/R) and BV2 microglia cells with oxygen and glucose deprivation/reoxygenation (OGD/R). A battery of behavioral tests, including the beam balance test, forelimb placement test, foot fault test, cylinder test, CatWalk gait analysis and Morris water maze test were performed to evaluate sensorimotor function, locomotor activity and cognitive ability. The expression of M1/M2-specific markers in the ischemic penumbra and BV2 microglia cells was detected using immunofluorescence staining, quantitative real-time PCR analysis and Western blot analysis. Our study showed that PLXNA2 knockdown accelerated the recovery of motor function and cognitive ability after MCAO/R. In addition, PLXNA2 knockdown restrained proinflammatory cytokine release and promoted anti-inflammatory cytokine release, and the mammalian target of rapamycin (mTOR)/signal transducer and activator of transcription 3 (STAT3) pathway was involved in PLXNA2 regulated microglia polarization. Taken together, our results indicate that PLXNA2 knockdown reduces neuroinflammation by switching the microglia phenotype from M1 to M2 in the ischemic penumbra of MCAO/R-injured rats, which may be due to the inhibition of mTOR/STAT3 signaling. Treatments targeting PLXNA2 may be a promising therapeutic strategy for ischemic stroke.

MIR21-induced loss of junctional adhesion molecule A promotes activation of oncogenic pathways, progression and metastasis in colorectal cancer.

Junctional adhesion molecules (JAMs) play a critical role in cell permeability, polarity and migration. JAM-A, a key protein of the JAM family, is altered in a number of conditions including cancer; however, consequences of JAM-A dysregulation on carcinogenesis appear to be tissue dependent and organ dependent with significant implications for the use of JAM-A as a biomarker or therapeutic target. Here, we test the expression and prognostic role of JAM-A downregulation in primary and metastatic colorectal cancer (CRC) (n = 947). We show that JAM-A downregulation is observed in ~60% of CRC and correlates with poor outcome in four cohorts of stages II and III CRC (n = 1098). Using JAM-A knockdown, re-expression and rescue experiments in cell line monolayers, 3D spheroids, patient-derived organoids and xenotransplants, we demonstrate that JAM-A silencing promotes proliferation and migration in 2D and 3D cell models and increases tumour volume and metastases in vivo. Using gene-expression and proteomic analyses, we show that JAM-A downregulation results in the activation of ERK, AKT and ROCK pathways and leads to decreased bone morphogenetic protein 7 expression. We identify MIR21 upregulation as the cause of JAM-A downregulation and show that JAM-A rescue mitigates the effects of MIR21 overexpression on cancer phenotype. Our results identify a novel molecular loop involving MIR21 dysregulation, JAM-A silencing and activation of multiple oncogenic pathways in promoting invasiveness and metastasis in CRC.

(Pro)renin Receptor Knockdown Attenuates Liver Fibrosis Through Inactivation of ERK/TGF-ß1/SMAD3 Pathway.

BACKGROUND & AIMS: Activation of the (pro)renin receptor (PRR) up-regulates the expression of profibrotic genes in the kidney and heart. We aimed to investigate the role of PRR in hepatic fibrogenesis. METHODS: Human hepatic PRR levels were measured in patients with or without liver fibrosis. PRR expression was analyzed in primary mouse hepatic stellate cells (HSCs). Experimental fibrosis was studied in thioacetamide (TAA)-treated or methionine choline-deficient (MCD) diet-fed C57BL/6 mice. Lentivirus-mediated PRR short hairpin RNA was used to knockdown hepatic PRR expression. Lentiviral vectors expressing PRR short hairpin RNA or complementary DNA from the α-smooth muscle actin promoter were used for myofibroblast-specific gene knockdown or overexpression. RESULTS: PRR is up-regulated in human and mouse fibrotic livers, and in activated HSCs. Hepatic PRR knockdown reduced liver fibrosis by suppressing the activation of HSCs and expression of profibrotic genes in TAA or MCD diet-injured mice without significant changes in hepatic inflammation. Renin and prorenin increased the expression of PRR and production of TGF-ß1 in human activated HSC Lieming Xu-2 cells, and knockdown of PRR inactivated Lieming Xu-2 cells with decreased production of transforming growth factor (TGF)-ß1 and Mothers against decapentaplegic homolog 3 (Smad3) phosphorylation. Myofibroblast-specific PRR knockdown also attenuated liver fibrosis in TAA or MCD diet-injured mice. Mice with both myofibroblast-specific and whole-liver PRR knockdown showed down-regulation of the hepatic extracellular signal-regulated kinase (ERK)/TGF-ß1/Smad3 pathway. Myofibroblast-specific PRR overexpression worsened TAA-induced liver fibrosis by up-regulating the ERK/TGF-ß1/Smad3 pathway. CONCLUSIONS: PRR contributes to liver fibrosis and HSC activation, and its down-regulation attenuates liver fibrosis through inactivation of the ERK/TGF-ß1/Smad3 pathway. Therefore, PRR is a promising therapeutic target for liver fibrosis.

Inactivation of Interleukin-4 Receptor α Signaling in Myeloid Cells Protects Mice From Angiotensin II/High Salt-Induced Cardiovascular Dysfunction Through Suppression of Fibrotic Remodeling.

Background Hypertension-induced cardiovascular remodeling is characterized by chronic low-grade inflammation. Interleukin-4 receptor α (IL-4Rα) signaling is importantly involved in cardiovascular remodeling, however, the target cell type(s) is unclear. Here, we investigated the role of myeloid-specific IL-4Rα signaling in cardiovascular remodeling induced by angiotensin II and high salt. Methods and Results Myeloid IL-4Rα deficiency suppressed both the in vitro and in vivo expression of alternatively activated macrophage markers including Arg1 (arginase 1), Ym1 (chitinase 3-like 3), and Relmα/Fizz1 (resistin-like molecule α). After angiotensin II and high salt treatment, myeloid-specific IL-4Rα deficiency did not change hypertrophic remodeling within the heart and aorta. However, myeloid IL-4Rα deficiency resulted in a substantial reduction in fibrosis through the suppression of profibrotic pathways and the enhancement of antifibrotic signaling. Decreased fibrosis was associated with significant preservation of myocardial function in MyIL4RαKO mice and was mediated by attenuated alternative macrophage activation. Conclusions Myeloid IL-4Rα signaling is substantially involved in fibrotic cardiovascular remodeling by controlling alternative macrophage activation and regulating fibrosis-related signaling. Inhibiting myeloid IL-4Rα signaling may be a potential strategy to prevent hypertensive cardiovascular diseases.

Interleukin 4 promotes anti-inflammatory macrophages that clear cartilage debris and inhibits osteoclast development to protect against osteoarthritis.

OBJECTIVE: Osteoarthritis (OA), the leading cause of joint failure, is characterized by breakdown of articular cartilage and remodeling of subchondral bone in synovial joints. Despite the high prevalence and debilitating effects of OA, no disease-modifying drugs exist. Increasing evidence, including genetic variants of the interleukin 4 (IL-4) and IL-4 receptor genes, implicates a role for IL-4 in OA, however, the mechanism underlying IL-4 function in OA remains unknown. Here, we investigated the role of IL-4 in OA pathogenesis. METHODS: Il4-, myeloid-specific-Il4ra-, and Stat6-deficient and control mice were subjected to destabilization of the medial meniscus to induce OA. Macrophages, osteoclasts, and synovial explants were stimulated with IL-4 in vitro, and their function and expression profiles characterized. RESULTS: Mice lacking IL-4, IL-4Ra in myeloid cells, or STAT6 developed exacerbated cartilage damage and osteophyte formation relative to WT controls. In vitro analyses revealed that IL-4 downregulates osteoarthritis-associated genes, enhances macrophage phagocytosis of cartilage debris, and inhibits osteoclast differentiation and activation via the type I receptor. CONCLUSION: Our findings demonstrate that IL-4 protects against osteoarthritis in a myeloid and STAT6-dependent manner. Further, IL-4 can promote an immunomodulatory microenvironment in which joint-resident macrophages polarize towards an M2 phenotype and efficiently clear pro-inflammatory debris, and osteoclasts maintain a homeostatic level of activity in subchondral bone. These findings support a role for IL-4 modulation of myeloid cell types in maintenance of joint health and identify a pathway that could provide therapeutic benefit for osteoarthritis.

CLEC5A knockdown protects against cardiac dysfunction after myocardial infarction by suppressing macrophage polarization, NLRP3 inflammasome activation, and pyroptosis.

Increasing evidence has shown that the NOD-like receptor protein 3 (NLRP3) inflammasome and pyroptotic cell death play vital roles in the pathophysiology of myocardial infarction (MI), a common cardiovascular disease characterized by cardiac dysfunction. C-type lectin member 5A (CLEC5A) has been reported to be strongly associated with activation of the NLRP3 inflammasome and pyroptosis. In this study, an in vivo MI model was established by ligation of the left anterior descending coronary artery in male C57BL/6 mice, and CLEC5A knockdown was further achieved by intra-myocardial injection of adenovirus delivering shRNA-CLEC5A. CLEC5A was found to be highly expressed in the left ventricle of MI mice, while CLEC5A knockdown alleviated cardiac dysfunction in MI mice. In addition, MI-induced classical activation of macrophages was significantly inhibited after CLEC5A silencing. Additionally, CLEC5A knockdown dramatically inhibited MI-triggered activation of NLRP3 inflammasome, pyroptosis, and NF-κB signaling in the left ventricle of mice. In vitro experiments further validated that CLEC5A knockdown suppressed M1 polarization in LPS/IFNγ-stimulated RAW264.7 cells and inhibited the polarized RAW264.7-induced activation of NLRP3 inflammasome/pyroptosis signaling in co-cultured cardiomyocytes. In conclusion, CLEC5A knockdown protects against MI-induced cardiac dysfunction by regulating macrophage polarization, NLRP3 inflammasome, and cell pyroptosis.

Loss of Soluble (Pro)renin Receptor Attenuates Angiotensin-II Induced Hypertension and Renal Injury.

[Figure: see text].

Tissue-selective alternate promoters guide NLRP6 expression.

The pryin domain (PYD) domain is involved in protein interactions that lead to assembly of immune-sensing complexes such as inflammasomes. The repertoire of PYD-containing genes expressed by a cell type arms tissues with responses against a range of stimuli. The transcriptional regulation of the PYD gene family however is incompletely understood. Alternative promoter utilization was identified as a mechanism regulating the tissue distribution of human PYD gene family members, including NLRP6 that is translationally silenced outside of intestinal tissue. Results show that alternative transcriptional promoters mediate NLRP6 silencing in mice and humans, despite no upstream genomic synteny. Human NLRP6 contains an internal alternative promoter within exon 2 of the PYD, resulting in a truncated mRNA in nonintestinal tissue. In mice, a proximal promoter was used that expanded the 5' leader sequence restricting nuclear export and abolishing translational efficiency. Nlrp6 was dispensable in disease models targeting the kidney, which expresses noncanonical isoforms. Thus, alternative promoter use is a critical mechanism not just for isoform modulation but for determining expression profile and function of PYD family members.

Cilia and polycystic kidney disease.

Polycystic kidney disease (PKD), comprising autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD), is characterized by incessant cyst formation in the kidney and liver. ADPKD and ARPKD represent the leading genetic causes of renal disease in adults and children, respectively. ADPKD is caused by mutations in PKD1 encoding polycystin1 (PC1) and PKD2 encoding polycystin 2 (PC2). PC1/2 are multi-pass transmembrane proteins that form a complex localized in the primary cilium. Predominant ARPKD cases are caused by mutations in polycystic kidney and hepatic disease 1 (PKHD1) gene that encodes the Fibrocystin/Polyductin (FPC) protein, whereas a small subset of cases are caused by mutations in DAZ interacting zinc finger protein 1 like (DZIP1L) gene. FPC is a type I transmembrane protein, localizing to the cilium and basal body, in addition to other compartments, and DZIP1L encodes a transition zone/basal body protein. Apparently, PC1/2 and FPC are signaling molecules, while the mechanism that cilia employ to govern renal tubule morphology and prevent cyst formation is unclear. Nonetheless, recent genetic and biochemical studies offer a glimpse of putative physiological malfunctions and the pathomechanisms underlying both disease entities. In this review, I summarize the results of genetic studies that deduced the function of PC1/2 on cilia and of cilia themselves in cyst formation in ADPKD, and I discuss studies regarding regulation of polycystin biogenesis and cilia trafficking. I also summarize the synergistic genetic interactions between Pkd1 and Pkhd1, and the unique tissue patterning event controlled by FPC, but not PC1. Interestingly, while DZIP1L mutations generate compromised PC1/2 cilia expression, FPC deficiency does not affect PC1/2 biogenesis and ciliary localization, indicating that divergent mechanisms could lead to cyst formation in ARPKD. I conclude by outlining promising areas for future PKD research and highlight rationales for potential therapeutic interventions for PKD treatment.

Myeloid interleukin-4 receptor α is essential in postmyocardial infarction healing by regulating inflammation and fibrotic remodeling.

Interleukin-4 receptor α (IL4Rα) signaling plays an important role in cardiac remodeling during myocardial infarction (MI). However, the target cell type(s) of IL4Rα signaling during this remodeling remains unclear. Here, we investigated the contribution of endogenous myeloid-specific IL4Rα signaling in cardiac remodeling post-MI. We established a murine myeloid-specific IL4Rα knockout (MyIL4RαKO) model with LysM promoter-driven Cre recombination. Macrophages from MyIL4RαKO mice showed significant downregulation of alternatively activated macrophage markers but an upregulation of classical activated macrophage markers both in vitro and in vivo, indicating the successful inactivation of IL4Rα signaling in macrophages. To examine the role of myeloid IL4Rα during MI, we subjected MyIL4RαKO and littermate floxed control (FC) mice to MI. We found that cardiac function was significantly impaired as a result of myeloid-specific IL4Rα deficiency. This deficiency resulted in a dysregulated inflammatory response consisting of decreased production of anti-inflammatory cytokines. Myeloid IL4Rα deficiency also led to reduced collagen 1 deposition and an imbalance of matrix metalloproteinases (MMPs)/tissue inhibitors of metalloproteinases (TIMPs), with upregulated MMPs and downregulated TIMPs, which resulted in insufficient fibrotic remodeling. In conclusion, this study identifies that myeloid-specific IL4Rα signaling regulates inflammation and fibrotic remodeling during MI. Therefore, myeloid-specific activation of IL4Rα signaling could offer protective benefits after MI.NEW & NOTEWORTHY This study showed, for the first time, the role of endogenous IL4Rα signaling in myeloid cells during cardiac remodeling and the underlying mechanisms. We identified myeloid cells are the critical target cell types of IL4Rα signaling during cardiac remodeling post-MI. Deficiency of myeloid IL4Rα signaling causes deteriorated cardiac function post-MI, due to dysregulated inflammation and insufficient fibrotic remodeling. This study sheds light on the potential of activating myeloid-specific IL4Rα signaling to modify remodeling post-MI. This brings hope to patients with MI and diminishes side effects by cell type-specific instead of whole body treatment.

Glucocorticoid Receptor Activation Restores Learning Memory by Modulating Hippocampal Plasticity in a Mouse Model of Brain Vitamin B12 Deficiency.

Cobalamin (Cbl, vitamin B12) deficiency or inborn errors of Cbl metabolism can produce neurologic disorders resistant to therapies, including cognitive dysfunction, mild mental retardation, memory impairment, and confusion. We used Cd320 KO mouse as a model for studying the pathological mechanisms of these disorders. Cd320 encodes the receptor (TCblR) needed for the cellular uptake of Cbl in the brain. The Cd320-/- mouse model presented an impaired learning memory that could be alleviated by a moderate stress, which produced also a greater increase of plasma corticosterone, compared to wild type animals. The present study investigated such a putative rescue mechanism in Cbl-deficient mice. At the molecular level in the brain of Cd320-/- mouse, the decreased methylation status led to a downregulation of glucocorticoid nuclear receptor (GR)/PPAR-gamma co-activator-1 alpha (PGC-1α) pathway. This was evidenced by the decreased expression of GR, decreased methylation of GR and PGC1α, and decreased dimerization and interaction of GR with PGC1α. This led to altered synaptic activity evidenced by decreased interaction between the NMDA glutamatergic receptor and the PSD95 post-synaptic protein and a lower expression of Egr-1 and synapsin 1, in Cd320-/- mice compared to the wild type animals. Intraperitoneal injection of hydrocortisone rescued these molecular changes and normalized the learning memory tests. Our study suggests adaptive influences of moderate stress on loss of memory and cognition due to brain Cbl deficiency. The GR pathway could be a potential target for innovative therapy of cognitive manifestations in patients with poor response to conventional Cbl treatment.

Overexpression of TGF-ß1 induces renal fibrosis and accelerates the decline in kidney function in polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the presence of numerous fluid-filled cysts, extensive fibrosis, and the progressive decline in kidney function. Transforming growth factor-ß1 (TGF-ß1), an important mediator for renal fibrosis and chronic kidney disease, is overexpressed by cystic cells compared with normal kidney cells; however, its role in PKD pathogenesis remains undefined. To investigate the effect of TGF-ß1 on cyst growth, fibrosis, and disease progression, we overexpressed active TGF-ß1 specifically in collecting ducts (CDs) of phenotypic normal (Pkd1RC/+) and Pkd1RC/RC mice. In normal mice, CD-specific TGF-ß1 overexpression caused tubule dilations by 5 wk of age that were accompanied by increased levels of phosphorylated SMAD3, α-smooth muscle actin, vimentin, and periostin; however, it did not induce overt cyst formation by 20 wk. In Pkd1RC/RC mice, CD overexpression of TGF-ß1 increased cyst epithelial cell proliferation. However, extensive fibrosis limited cyst enlargement and caused contraction of the kidneys, leading to a loss of renal function and a shortened lifespan of the mice. These data demonstrate that TGF-ß1-induced fibrosis constrains cyst growth and kidney enlargement and accelerates the decline of renal function, supporting the hypothesis that a combined therapy that inhibits renal cyst growth and fibrosis will be required to effectively treat ADPKD.

The DARC-null trait is associated with moderate modulation of NK cell profiles and unaltered cytolytic T cell profiles in black South Africans.

The Duffy Antigen Receptor for Chemokines (DARC)-null trait, common among persons of African descent and associated with lower absolute neutrophil counts (ANCs), may be linked to increased risk to certain infections including HIV-1 but the underlying causes are poorly understood. We hypothesized that DARC-null-linked neutropenia may negatively impact neutrophil immunoregulatory modulation of other immune cells such as natural killer (NK) and CD8+ T cells leading to altered phenotype, functionality and homeostatic activity of these immune cells. HIV-1 uninfected (n = 20) and HIV-1 chronically infected (n = 19) participants were assessed using multi-parametric flow cytometry to determine NK and CD8+ T cell counts, phenotypic profiles, and cytokine production and degranulation. Annexin V and carboxyfluorescein succinimidyl ester (CFSE) staining were used to examine NK cell survival and NK cell and CD8+ T cell proliferation respectively. Participants were genotyped for the DARC-null polymorphism using allelic discrimination assays and ANCs were measured by full blood count. In HIV uninfected individuals, a reduction of total NK cell counts was noted in the absence of DARC and this correlated with lower ANCs. HIV uninfected DARC-null subjects displayed a less mature NK cell phenotype. However, this did not translate to differences in NK cell activation or effector functionality by DARC state. Whilst HIV-1 infected subjects displayed NK cell profiling that is typical of HIV infection, no differences were noted upon DARC stratification. Similarly, CD8+ T cells from HIV infected individuals displayed phenotypic and functional modulation that is characteristic of HIV infection, but profiling was unaffected by the DARC-null variant irrespective of HIV status. Overall, the data suggests that the DARC-null polymorphism and lower ANCs does not impede downstream cytolytic cell priming and functionality.