Pericyte MyD88 and IRAK4 control inflammatory and fibrotic responses to tissue injury

Targeting inflammation in perivascular cells and neuroimmune interactions for treating kidney disease

Inflammation plays a crucial role in the pathophysiology of various kidney diseases. Kidney perivascular cells (pericytes/fibroblasts) are responsible for producing proinflammatory molecules, promoting immune cell infiltration, and enhancing inflammation. Vascular adhesion protein-1, expressed in kidney perivascular cells, is an ectoenzyme that catalyzes the oxidative deamination of primary amines with the production of hydrogen peroxide in the extracellular space. Our study demonstrated that blocking this enzyme suppressed hydrogen peroxide production and neutrophil infiltration, thereby reducing renal ischemia-reperfusion injury. Sphingosine 1-phosphate (S1P) signaling was also observed to play an essential role in the regulation of perivascular inflammation. S1P, which is produced in kidney perivascular cells, is transported into the extracellular space via spinster homolog 2, and then binds to S1P receptor-1 expressed in perivascular cells. Upon injury, inflammatory signaling in perivascular cells is enhanced by this pathway, thereby promoting immune cell infiltration and subsequent fibrosis. Furthermore, inhibition of S1P transport by spinster homolog 2 reduces kidney fibrosis. Hypoxia-inducible factor-prolyl hydroxylase inhibitors can restore the capacity for erythropoietin production in kidney perivascular cells. Animal data suggested that these drugs could also alleviate kidney and lipid inflammation although the precise mechanism is still unknown. Neuroimmune interactions have been attracting significant attention due to their potential to benefit patients with inflammatory diseases. Vagus nerve stimulation is one of the most promising strategies for harnessing neuroimmune interactions and attenuating inflammation associated with various diseases, including kidney disease. Using cutting-edge tools, the vagal afferents-C1 neurons-sympathetic nervous system-splenic nerve-spleen-kidney axis responsible for kidney protection induced by vagus nerve stimulation was identified in our study. Further research is required to decipher other crucial systems that control kidney inflammation and to determine whether these novel strategies can be applied to patients with kidney disease.

The protective role of vagus nerve stimulation in ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) encompasses the damage resulting from the restoration of blood supply following tissue ischemia. This phenomenon commonly occurs in clinical scenarios such as hemorrhagic shock, severe trauma, organ transplantation, and thrombolytic therapy. Despite its prevalence, existing treatments exhibit limited efficacy against IRI. Vagus nerve stimulation (VNS) is a widely utilized technique for modulating the autonomic nervous system. Numerous studies have demonstrated that VNS significantly reduces IRI in various organs, including the heart, brain, and liver. This article reviews the pathological processes during IRI and summarizes the role and possible mechanisms of VNS in IRI of different organs. Furthermore, this review addresses the current challenges of VNS clinical applications, providing a novel perspective on IRI treatment.

The fate and role of the pericytes in myocardial diseases

The adult mammalian heart contains a large population of pericytes that play important roles in homeostasis and disease. In the normal heart, pericytes regulate microvascular permeability and flow. Myocardial diseases are associated with marked alterations in pericyte phenotype and function. This review manuscript discusses the role of pericytes in cardiac homeostasis and disease. Following myocardial infarction (MI), cardiac pericytes participate in all phases of cardiac repair. During the inflammatory phase, pericytes may secrete cytokines and chemokines and may regulate leukocyte trafficking, through formation of intercellular gaps that serve as exit points for inflammatory cells. Moreover, pericyte contraction induces microvascular constriction, contributing to the pathogenesis of 'no-reflow' in ischemia and reperfusion. During the proliferative phase, pericytes are activated by growth factors, such as transforming growth factor (TGF)-β and contribute to fibrosis, predominantly through secretion of fibrogenic mediators. A fraction of pericytes acquires fibroblast identity but contributes only to a small percentage of infarct fibroblasts and myofibroblasts. As the scar matures, pericytes form a coat around infarct neovessels, promoting stabilization of the vasculature. Pericytes may also be involved in the pathogenesis of chronic heart failure, by regulating inflammation, fibrosis, angiogenesis and myocardial perfusion. Pericytes are also important targets of viral infections (such as SARS-CoV2) and may be implicated in the pathogenesis of cardiac complications of COVID19. Considering their role in myocardial inflammation, fibrosis and angiogenesis, pericytes may be promising therapeutic targets in myocardial disease.

Mechanisms of inflammation modulation by different immune cells in hypertensive nephropathy

Hypertensive nephropathy (HTN) is the second leading cause of end-stage renal disease (ESRD) and a chronic inflammatory disease. Persistent hypertension leads to lesions of intrarenal arterioles and arterioles, luminal stenosis, secondary ischemic renal parenchymal damage, and glomerulosclerosis, tubular atrophy, and interstitial fibrosis. Studying the pathogenesis of hypertensive nephropathy is a prerequisite for diagnosis and treatment. The main cause of HTN is poor long-term blood pressure control, but kidney damage is often accompanied by the occurrence of immune inflammation. Some studies have found that the activation of innate immunity, inflammation and acquired immunity is closely related to the pathogenesis of HTN, which can cause damage and dysfunction of target organs. There are more articles on the mechanism of diabetic nephropathy, while there are fewer studies related to immunity in hypertensive nephropathy. This article reviews the mechanisms by which several different immune cells and inflammatory cytokines regulate blood pressure and renal damage in HTN. It mainly focuses on immune cells, cytokines, and chemokines and inhibitors. However, further comprehensive and large-scale studies are needed to determine the role of these markers and provide effective protocols for clinical intervention and treatment.

The role of cardiac pericytes in health and disease: therapeutic targets for myocardial infarction

Millions of cardiomyocytes die immediately after myocardial infarction, regardless of whether the culprit coronary artery undergoes prompt revascularization. Residual ischaemia in the peri-infarct border zone causes further cardiomyocyte damage, resulting in a progressive decline in contractile function. To date, no treatment has succeeded in increasing the vascularization of the infarcted heart. In the past decade, new approaches that can target the heart's highly plastic perivascular niche have been proposed. The perivascular environment is populated by mesenchymal progenitor cells, fibroblasts, myofibroblasts and pericytes, which can together mount a healing response to the ischaemic damage. In the infarcted heart, pericytes have crucial roles in angiogenesis, scar formation and stabilization, and control of the inflammatory response. Persistent ischaemia and accrual of age-related risk factors can lead to pericyte depletion and dysfunction. In this Review, we describe the phenotypic changes that characterize the response of cardiac pericytes to ischaemia and the potential of pericyte-based therapy for restoring the perivascular niche after myocardial infarction. Pericyte-related therapies that can salvage the area at risk of an ischaemic injury include exogenously administered pericytes, pericyte-derived exosomes, pericyte-engineered biomaterials, and pharmacological approaches that can stimulate the differentiation of constitutively resident pericytes towards an arteriogenic phenotype. Promising preclinical results from in vitro and in vivo studies indicate that pericytes have crucial roles in the treatment of coronary artery disease and the prevention of post-ischaemic heart failure.

The role and mechanism of RIPK1 in vascular endothelial dysfunction in chronic kidney disease

Endothelial dysfunction is common in patients with chronic kidney disease (CKD) and cardiovascular events, but the mechanism is unclear. In our study, we found elevated levels of RIPK1 in patients with CKD and cardiovascular events through bioinformation analysis. Elevated RIPK1 levels were found in serum samples of CKD patients and were associated with vascular endothelial dysfunction and renal function. We constructed the five of six nephrectomy of CKD mice model, finding that RIPK1 expressions were elevated in abdominal aorta endothelial cells. After RIPK1 inhibition and overexpression, it was found that RIPK1 could regulate the expression of endothelial nitric oxide synthase (eNOS) and cell adhesion molecule 1 (ICAM-1), and activation of inflammatory responses and endoplasmic reticulum (ER) stress. In addition, uremic toxin induced abnormal expression of RIPK1 in vitro. We observed RIPK1-mediating endothelial dysfunction and inflammation responses by ER stress pathways through gain and loss of function. In order to explore the specific mechanism, we conducted co-immunoprecipitation and expression regulation of RIPK1 and IKK, finding that RIPK1 formed complex with IKK and regulated IKK expression. In conclusion, we demonstrated that RIPK1 levels were closely associated with vascular endothelial dysfunction in patients with CKD. With uremic toxins, RIPK1 expression was elevated, which led to the activation of inflammation through the ER stress pathway, resulting in vascular endothelial injury. Besides, activation of RIPK1-IKK-NF-κB axis was a key driver of endothelial dysfunction in CKD. Our study provides a new perspective for the study of cardiovascular events in CKD.

Role of perivascular cells in kidney homeostasis, inflammation, repair and fibrosis

Perivascular niches in the kidney comprise heterogeneous cell populations, including pericytes and fibroblasts, with distinct functions. These perivascular cells have crucial roles in preserving kidney homeostasis as they maintain microvascular networks by stabilizing the vasculature and regulating capillary constriction. A subset of kidney perivascular cells can also produce and secrete erythropoietin; this ability can be enhanced with hypoxia-inducible factor-prolyl hydroxylase inhibitors, which are used to treat anaemia in chronic kidney disease. In the pathophysiological state, kidney perivascular cells contribute to the progression of kidney fibrosis, partly via transdifferentiation into myofibroblasts. Moreover, perivascular cells are now recognized as major innate immune sentinels in the kidney that produce pro-inflammatory cytokines and chemokines following injury. These mediators promote immune cell infiltration, leading to persistent inflammation and progression of kidney fibrosis. The crosstalk between perivascular cells and tubular epithelial, immune and endothelial cells is therefore a key process in physiological and pathophysiological states. Here, we examine the multiple roles of kidney perivascular cells in health and disease, focusing on the latest advances in this field of research.

Divergent Actions of Renal Tubular and Endothelial Type 1 IL-1 Receptor Signaling in Toxin-Induced AKI

SIGNIFICANCE STATEMENT

Activation of the type 1 IL-1 receptor (IL-1R1) triggers a critical innate immune signaling cascade that contributes to the pathogenesis of AKI. However, blockade of IL-1 signaling in AKI has not consistently demonstrated kidney protection. The current murine experiments show that IL-1R1 activation in the proximal tubule exacerbates toxin-induced AKI and cell death through local suppression of apolipoprotein M. By contrast, IL-1R1 activation in endothelial cells ameliorates AKI by restoring VEGFA-dependent endothelial cell viability. Using this information, future delivery strategies can maximize the protective effects of blocking IL-1R1 while mitigating unwanted actions of IL-1R1 manipulation.

BACKGROUND

Activation of the type 1 IL-1 receptor (IL-1R1) triggers a critical innate immune signaling cascade that contributes to the pathogenesis of AKI. IL-1R1 is expressed on some myeloid cell populations and on multiple kidney cell lineages, including tubular and endothelial cells. Pharmacological inhibition of the IL-1R1 does not consistently protect the kidney from injury, suggesting there may be complex, cell-specific effects of IL-1R1 stimulation in AKI.

METHODS

To examine expression of IL-1 and IL-1R1 in intrinsic renal versus infiltrating immune cell populations during AKI, we analyzed single-cell RNA sequencing (scRNA-seq) data from kidney tissues of humans with AKI and mice with acute aristolochic acid exposure. We then investigated cell-specific contributions of renal IL-1R1 signaling to AKI using scRNA-seq, RNA microarray, and pharmacological interventions in mice with IL-1R1 deletion restricted to the proximal tubule or endothelium.

RESULTS

scRNA-seq analyses demonstrated robust IL-1 expression in myeloid cell populations and low-level IL-1R1 expression in kidney parenchymal cells during toxin-induced AKI. Our genetic studies showed that IL-1R1 activation in the proximal tubule exacerbated toxin-induced AKI and cell death through local suppression of apolipoprotein M. By contrast, IL-1R1 activation in endothelial cells ameliorated aristolochic acid-induced AKI by restoring VEGFA-dependent endothelial cell viability and density.

CONCLUSIONS

These data highlight opposing cell-specific effects of IL-1 receptor signaling on AKI after toxin exposure. Disrupting pathways activated by IL-1R1 in the tubule, while preserving those triggered by IL-1R1 activation on endothelial cells, may afford renoprotection exceeding that of global IL-1R1 inhibition while mitigating unwanted actions of IL-1R1 blockade.

Cardiac Pericytes Acquire a Fibrogenic Phenotype and Contribute to Vascular Maturation After Myocardial Infarction

BACKGROUND

Pericytes have been implicated in tissue repair, remodeling, and fibrosis. Although the mammalian heart contains abundant pericytes, their fate and involvement in myocardial disease remains unknown.

METHODS

We used NG2Dsred;PDGFRαEGFP pericyte:fibroblast dual reporter mice and inducible NG2CreER mice to study the fate and phenotypic modulation of pericytes in myocardial infarction. The transcriptomic profile of pericyte-derived cells was studied using polymerase chain reaction arrays and single-cell RNA sequencing. The role of transforming growth factor-β (TGF-β) signaling in regulation of pericyte phenotype was investigated in vivo using pericyte-specific TGF-β receptor 2 knockout mice and in vitro using cultured human placental pericytes.

RESULTS

In normal hearts, neuron/glial antigen 2 (NG2) and platelet-derived growth factor receptor α (PDGFRα) identified distinct nonoverlapping populations of pericytes and fibroblasts, respectively. After infarction, a population of cells expressing both pericyte and fibroblast markers emerged. Lineage tracing demonstrated that in the infarcted region, a subpopulation of pericytes exhibited transient expression of fibroblast markers. Pericyte-derived cells accounted for ~4% of PDGFRα+ infarct fibroblasts during the proliferative phase of repair. Pericyte-derived fibroblasts were overactive, expressing higher levels of extracellular matrix genes, integrins, matricellular proteins, and growth factors, when compared with fibroblasts from other cellular sources. Another subset of pericytes contributed to infarct angiogenesis by forming a mural cell coat, stabilizing infarct neovessels. Single-cell RNA sequencing showed that NG2 lineage cells diversify after infarction and exhibit increased expression of matrix genes, and a cluster with high expression of fibroblast identity markers emerges. Trajectory analysis suggested that diversification of infarct pericytes may be driven by proliferating cells. In vitro and in vivo studies identified TGF-β as a potentially causative mediator in fibrogenic activation of infarct pericytes. However, pericyte-specific TGF-β receptor 2 disruption had no significant effects on infarct myofibroblast infiltration and collagen deposition. Pericyte-specific TGF-β signaling was involved in vascular maturation, mediating formation of a mural cell coat investing infarct neovessels and protecting from dilative remodeling.

CONCLUSIONS

In the healing infarct, cardiac pericytes upregulate expression of fibrosis-associated genes, exhibiting matrix-synthetic and matrix-remodeling profiles. A fraction of infarct pericytes exhibits expression of fibroblast identity markers. Pericyte-specific TGF-β signaling plays a central role in maturation of the infarct vasculature and protects from adverse dilative remodeling, but it does not modulate fibrotic remodeling.

Beneficiary Effects of Colchicine on Inflammation and Fibrosis in a Mouse Model of Kidney Injury

INTRODUCTION

Low-grade inflammation is seen in many chronic illnesses, including chronic kidney disease (CKD). We have recently reported on beneficiary effects of anti-inflammatory treatment in the interleukin (IL-) 1 pathway on anemia as well as CKD extent in a mouse model. Colchicine has been shown to have beneficiary effects in several inflammatory conditions through various mechanisms, including inhibition of tubulin polymerization as well as caspase-1-mediated IL-1 activation.

METHODS

Kidney injury (KI) was induced by administering an adenine diet to 8-week-old C57BL/6J mice treated with colchicine (Col) (30 µg/kg) or saline injections for 3 weeks, generating 4 groups: C, Ccol, KI, and KIcol.

RESULTS

KI animals had an increase in inflammation indices in the blood (neutrophils), liver, and kidneys (uromodulin, IL-6, pSTAT3). Increased kidney tubulin polymerization and caspase-1 in KI, as well as kidney Mid88 and IRAK4 (downstream of IL-1), were inhibited in KIcol. Kidney macrophage and polymorphonuclear infiltration (positive for F4/80 and MPO, respectively), the percentage of fibrotic area, and TGFβ mRNA levels were lower in KIcol versus KI.

CONCLUSIONS

Colchicine inhibited tubulin polymerization and caspase-1 activation and attenuated kidney inflammation and fibrosis in a mouse model of adenine-induced KI. Given its reported safety profile for long-term anti-inflammatory therapy without increasing infection tendency, it may serve as novel therapeutic approach in CKD.

Regulation of pericyte metabolic reprogramming restricts the AKI to CKD transition

BACKGROUND AND AIMS

Acute kidney injury (AKI) is associated with high morbidity and mortality and is recognized as a long-term risk factor for progression to chronic kidney disease (CKD). The AKI to CKD transition is characterized by interstitial fibrosis and the proliferation of collagen-secreting myofibroblasts. Pericytes are the major source of myofibroblasts in kidney fibrosis. However, the underlying mechanism of pericyte-myofibroblast transition (PMT) is still unclear. Here we investigated the role of metabolic reprogramming in PMT.

METHODS

Unilateral ischemia/reperfusion-induced AKI to CKD mouse model and TGF-β-treated pericyte-like cells were used to detect the levels of fatty acid oxidation (FAO) and glycolysis, and the critical signaling pathways during PMT under the treatment of drugs regulating metabolic reprogramming.

RESULTS

PMT is characterized by a decrease in FAO and an increase in glycolysis. Enhancement of FAO by the peroxisome proliferator-activated receptor gamma coactivator-1α (PGC1α) activator ZLN-005 or suppression of glycolysis by the hexokinase 2 (HK2) inhibitor 2-DG can inhibit PMT, preventing the transition of AKI to CKD. Mechanistically, AMPK modulates various pathways involved in the metabolic switch from glycolysis to FAO. Specifically, the PGC1α-CPT1A pathway activates FAO, while inhibition of the HIF1α-HK2 pathway drives glycolysis inhibition. The modulations of these pathways by AMPK contribute to inhibiting PMT.

CONCLUSIONS

Metabolic reprogramming controls the fate of pericyte transdifferentiation and targets the abnormal metabolism of pericytes can effectively prevent AKI to CKD transition.

Design, synthesis, and pharmacological evaluation of N-(3-carbamoyl-1H-pyrazol-4-yl)-1,3-oxazole-4-carboxamide derivatives as interleukin-1 receptor-associated kinase 4 inhibitors with reduced potential for cytochrome P450 1A2 induction

Interleukin-1 receptor-associated kinase 4 (IRAK4) is a critical molecule in Toll-like receptor/interleukin-1 receptor signaling and an attractive therapeutic target for a wide range of inflammatory and autoimmune diseases as well as cancers. In our search for novel IRAK4 inhibitors, we conducted structural modification of a thiazolecarboxamide derivative 1, a lead compound derived from high-throughput screening hits, to elucidate structure-activity relationship and improve drug metabolism and pharmacokinetic (DMPK) properties. First, conversion of the thiazole ring of 1 to an oxazole ring along with introduction of a methyl group at the 2-position of the pyridine ring aimed at reducing cytochrome P450 (CYP) inhibition were conducted to afford 16. Next, modification of the alkyl substituent at the 1-position of the pyrazole ring of 16 aimed at improving CYP1A2 induction properties revealed that branched alkyl and analogous substituents such as isobutyl (18) and (oxolan-3-yl)methyl (21), as well as six-membered saturated heterocyclic groups such as oxan-4-yl (2), piperidin-4-yl (24, 25), and dioxothian-4-y (26), are effective for reducing induction potential. Representative compound AS2444697 (2) exhibited potent IRAK4 inhibitory activity with an IC50 value of 20 nM and favorable DMPK properties such as low risk of drug-drug interactions mediated by CYPs as well as excellent metabolic stability and oral bioavailability.

FOXP3+ macrophage represses acute ischemic stroke-induced neural inflammation

Proper termination of cell-death-induced neural inflammation is the premise of tissue repair in acute ischemic stroke (AIS). Macrophages scavenge cell corpses/debris and produce inflammatory mediators that orchestrate immune responses. Here, we report that FOXP3, the key immune-repressive transcription factor of Tregs, is conditionally expressed in macrophages in stroke lesion. FOXP3 ablation in macrophages results in detrimental stroke outcomes, emphasizing the beneficial role of FOXP3+ macrophages. FOXP3+ macrophages are distinct from the M1 or M2 subsets and display superactive efferocytic capacity. With scRNAseq and analysis of FOXP3-bound-DNA isolated with CUT & RUN, we show that FOXP3 facilitates macrophage phagocytosis through enhancing cargo metabolism. FOXP3 expression is controlled by macroautophagic/autophagic protein degradation in resting macrophages, while initiation of LC3-associated phagocytosis (LAP) competitively occupies the autophagic machineries, and thus permits FOXP3 activation. Our data demonstrate a distinct set of FOXP3+ macrophages with enhanced scavenging capability, which could be a target in immunomodulatory therapy against AIS.Abbreviations: ADGRE1/F4/80: adhesion G protein-coupled receptor E1; AIF1/Iba1: allograft inflammatory factor 1; AIS: acute ischemic stroke; ARG1: arginase 1; ATP: adenosine triphosphate; BECN1/Beclin1: Beclin 1, autophagy related; BMDM: bone marrow-derived macrophages; CKO: conditional knockout; CSF1/M-CSF: colony stimulating factor 1 (macrophage); CSF2/GM-CSF: colony stimulating factor 2; CSF3/G-CSF: colony stimulating factor 3; CUT & RUN: cleavage under targets and release using nuclease; CyD: cytochalasin D; DAMP: danger/damage-associated molecular pattern; DIL: dioctadecyl-3,3,3,3-tetramethylin docarbocyanine; ELISA: enzyme linked immunosorbent assay; GO: Gene Ontology; FCGR3/CD16: Fc receptor, IgG, low affinity III; HMGB1: high mobility group box 1; IFNG/IFNγ: interferon gamma; IP: immunoprecipitation; KEGG: Kyoto Encyclopedia of Genes and Genomes; ITGAM/CD11b: integrin subunit alpha M; ITGAX/CD11c: integrin subunit alpha X; LAP: LC3-associated phagocytosis; LC-MS: liquid chromatography-mass spectrometry; LPS: lipopolysaccharide; MRC1/CD206: mannose receptor, C type 1; O4: oligodendrocyte marker O4; PBMC: peripheral blood mononuclear cells; RBC: red blood cells; PTPRC/CD45: protein tyrosine phosphatase, receptor type, C; RBFOX3/NeuN: RNA binding protein, fox 1 homolog (C. elegans) 3; RUBCN/Rubicon: RUN domain and cysteine-rich domain containing, Beclin 1-interacting protein; scRNAseq: single cell RNA sequencing; SQSTM1/p62 (sequestosome 1); TGFB/TGFβ: transforming growth factor, beta; tMCAO: transient middle cerebral artery occlusion; TNF/TNFα: tumor necrosis factor; Treg: regulatory T cell.

Diabetes Induces Cardiac Fibroblast Activation, Promoting a Matrix-Preserving Nonmyofibroblast Phenotype, Without Stimulating Pericyte to Fibroblast Conversion

Background Interstitial and perivascular fibrosis may contribute to diabetes-associated heart failure. Pericytes can convert to fibroblasts under conditions of stress and have been implicated in the pathogenesis of fibrotic diseases. We hypothesized that in diabetic hearts, pericytes may convert to fibroblasts, contributing to fibrosis and to the development of diastolic dysfunction. Methods and Results Using pericyte:fibroblast dual reporter (NG2^Dsred [neuron-glial antigen 2 red fluorescent protein variant]; PDGFRα^EGFP [platelet-derived growth factor receptor alpha enhanced green fluorescent protein]) mice in a type 2 diabetic db/db background, we found that diabetes does not significantly affect pericyte density but reduces the myocardial pericyte:fibroblast ratio. Lineage tracing using the inducible NG2^CreER driver, along with reliable labeling of fibroblasts with the PDGFRα reporter system, showed no significant pericyte to fibroblast conversion in lean and db/db hearts. In addition, db/db mouse cardiac fibroblasts did not undergo myofibroblast conversion and had no significant induction of structural collagens but exhibited a matrix-preserving phenotype, associated with increased expression of antiproteases, matricellular genes, matrix cross-linking enzymes, and the fibrogenic transcription factor cMyc. In contrast, db/db mouse cardiac pericytes had increased expression of Timp3, without any changes in expression of other fibrosis-associated genes. The matrix-preserving phenotype of diabetic fibroblasts was associated with induction of genes encoding oxidative (Ptgs2/cycloxygenase-2, and Fmo2) and antioxidant proteins (Hmox1, Sod1). In vitro, high glucose partially recapitulated the in vivo changes in diabetic fibroblasts. Conclusions Diabetic fibrosis is not mediated through pericyte to fibroblast conversion but involves acquisition of a matrix-preserving fibroblast program, which is independent of myofibroblast conversion and is only partially explained by the effects of the hyperglycemic environment.

Pericytes modulate islet immune cells and insulin secretion through Interleukin-33 production in mice

Introduction

Immune cells were recently shown to support β-cells and insulin secretion. However, little is known about how islet immune cells are regulated to maintain glucose homeostasis. Administration of various cytokines, including Interleukin-33 (IL-33), was shown to influence β-cell function. However, the role of endogenous, locally produced IL-33 in pancreatic function remains unknown. Here, we show that IL-33, produced by pancreatic pericytes, is required for glucose homeostasis.

Methods

To characterize pancreatic IL-33 production, we employed gene expression, flow cytometry, and immunofluorescence analyses. To define the role of this cytokine, we employed transgenic mouse systems to delete the Il33 gene selectively in pancreatic pericytes, in combination with the administration of recombinant IL-33. Glucose response was measured in vivo and in vitro, and morphometric and molecular analyses were used to measure β-cell mass and gene expression. Immune cells were analyzed by flow cytometry.

Resuts

Our results show that pericytes are the primary source of IL-33 in the pancreas. Mice lacking pericytic IL-33 were glucose intolerant due to impaired insulin secretion. Selective loss of pericytic IL-33 was further associated with reduced T and dendritic cell numbers in the islets and lower retinoic acid production by islet macrophages.

Discussion

Our study demonstrates the importance of local, pericytic IL-33 production for glucose regulation. Additionally, it proposes that pericytes regulate islet immune cells to support β-cell function in an IL-33-dependent manner. Our study reveals an intricate cellular network within the islet niche.

Pathogenesis of lupus nephritis: the contribution of immune and kidney resident cells

PURPOSE OF REVIEW

Lupus nephritis is associated with significant mortality and morbidity. We lack effective therapeutics and biomarkers mostly because of our limited understanding of its complex pathogenesis. We aim to present an overview of the recent advances in the field to gain a deeper understanding of the underlying cellular and molecular mechanisms involved in lupus nephritis pathogenesis.

RECENT FINDINGS

Recent studies have identified distinct roles for each resident kidney cell in the pathogenesis of lupus nephritis. Podocytes share many elements of innate and adaptive immune cells and they can present antigens and participate in the formation of crescents in coordination with parietal epithelial cells. Mesangial cells produce pro-inflammatory cytokines and secrete extracellular matrix contributing to glomerular fibrosis. Tubular epithelial cells modulate the milieu of the interstitium to promote T cell infiltration and formation of tertiary lymphoid organs. Modulation of specific genes in kidney resident cells can ward off the effectors of the autoimmune response including autoantibodies, cytokines and immune cells.

SUMMARY

The development of lupus nephritis is multifactorial involving genetic susceptibility, environmental triggers and systemic inflammation. However, the role of resident kidney cells in the development of lupus nephritis is becoming more defined and distinct. More recent studies point to the restoration of kidney resident cell function using cell targeted approaches to prevent and treat lupus nephritis.

Toll-like Receptor 4 in Acute Kidney Injury

Acute kidney injury (AKI) is a common and devastating pathologic condition, associated with considerable high morbidity and mortality. Although significant breakthroughs have been made in recent years, to this day no effective pharmacological therapies for its treatment exist. AKI is known to be connected with intrarenal and systemic inflammation. The innate immune system plays an important role as the first defense response mechanism to tissue injury. Toll-like receptor 4 (TLR4) is a well-characterized pattern recognition receptor, and increasing evidence has shown that TLR4 mediated inflammatory response, plays a pivotal role in the pathogenesis of acute kidney injury. Pathogen-associated molecular patterns (PAMPS), which are the conserved microbial motifs, are sensed by these receptors. Endogenous molecules generated during tissue injury, and labeled as damage-associated molecular pattern molecules (DAMPs), also activate pattern recognition receptors, thereby offering an understanding of sterile types of inflammation. Excessive, uncontrolled and/or sustained activation of TLR4, may lead to a chronic inflammatory state. In this review we describe the role of TLR4, its endogenous ligands and activation in the inflammatory response to ischemic/reperfusion-induced AKI and sepsis-associated AKI. The potential regeneration signaling patterns of TLR4 in acute kidney injury, are also discussed.

Targeting innate immunity-driven inflammation in CKD and cardiovascular disease

Mortality among patients with chronic kidney disease (CKD) is largely a consequence of cardiovascular disease (CVD) and is a particular concern given the increasing prevalence of CKD. Sterile inflammation triggered by activation of the innate immune system is an important driver of both CKD and associated CVD. Several endogenous mediators, including lipoproteins, crystals such as silica, urate and cholesterol crystals, or compounds released from dying cells interact with pattern recognition receptors expressed on a variety of different cell types, leading to the release of pro-inflammatory cytokines. Disturbed regulation of the haematopoietic system by damage-associated molecular patterns, or as a consequence of clonal haematopoiesis or trained innate immunity, also contributes to the development of inflammation. In observational and genetic association studies, inflammation is linked to the progression of CKD and cardiovascular events. In 2017, the CANTOS trial of canakinumab provided evidence that inhibiting inflammation driven by NLRP3-IL-1-IL-6-mediated signalling significantly reduced cardiovascular event rates in individuals with and without CKD. Other approaches to target innate immune pathways are now under investigation for their ability to reduce cardiovascular events and slow disease progression among patients with atherosclerosis and stage 3 and 4 CKD. This Review summarizes current understanding of the role of inflammation in the pathogenesis of CKD and its associated CVD, and how this knowledge may translate into novel therapeutics.

Sphingosine 1-phosphate signaling in perivascular cells enhances inflammation and fibrosis in the kidney

Chronic kidney disease (CKD), characterized by sustained inflammation and progressive fibrosis, is highly prevalent and can eventually progress to end-stage kidney disease. However, current treatments to slow CKD progression are limited. Sphingosine 1-phosphate (S1P), a product of sphingolipid catabolism, is a pleiotropic mediator involved in many cellular functions, and drugs targeting S1P signaling have previously been studied particularly for autoimmune diseases. The primary mechanism of most of these drugs is functional antagonism of S1P receptor-1 (S1P1) expressed on lymphocytes and the resultant immunosuppressive effect. Here, we documented the role of local S1P signaling in perivascular cells in the progression of kidney fibrosis using primary kidney perivascular cells and several conditional mouse models. S1P was predominantly produced by sphingosine kinase 2 in kidney perivascular cells and exported via spinster homolog 2 (Spns2). It bound to S1P1 expressed in perivascular cells to enhance production of proinflammatory cytokines/chemokines upon injury, leading to immune cell infiltration and subsequent fibrosis. A small-molecule Spns2 inhibitor blocked S1P transport, resulting in suppression of inflammatory signaling in human and mouse kidney perivascular cells in vitro and amelioration of kidney fibrosis in mice. Our study provides insight into the regulation of inflammation and fibrosis by S1P and demonstrates the potential of Spns2 inhibition as a treatment for CKD and potentially other inflammatory and fibrotic diseases that avoids the adverse events associated with systemic modulation of S1P receptors.

Autoantibodies in systemic lupus erythematosus: From immunopathology to therapeutic target

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multiple organ inflammatory damage and wide spectrum of autoantibodies. The autoantibodies, especially anti-dsDNA and anti-Sm autoantibodies are highly specific to SLE, and participate in the immune complex formation and inflammatory damage on multiple end-organs such as kidney, skin, and central nervous system (CNS). However, the underlying mechanisms of autoantibody-induced tissue damage and systemic inflammation are still not fully understood. Single cell analysis of autoreactive B cells and monoclonal antibody screening from patients with active SLE has improved our understanding on the origin of autoreactive B cells and the antigen targets of the pathogenic autoantibodies. B cell depletion therapies have been widely studied in the clinics, but the development of more specific therapies against the pathogenic B cell subset and autoantibodies with improved efficacy and safety still remain a big challenge. A more comprehensive autoantibody profiling combined with functional characterization of autoantibodies in diseases development will shed new insights on the etiology and pathogenesis of SLE and guide a specific treatment to individual SLE patients.

MyD88 in hepatic stellate cells enhances liver fibrosis via promoting macrophage M1 polarization

During liver fibrosis, quiescent HSCs (qHSCs) are activated to become activated HSCs (aHSCs)/myofibroblasts. The signal adapter MyD88, an essential component of TLR signaling, plays an important role in liver fibrosis. However, far less is known about the specific effects of MyD88 signaling in both qHSCs and aHSCs in the progress of liver fibrosis. Here, we used a CCl₄-induced mouse fibrosis model in which MyD88 was selectively depleted in qHSCs (GFAP^MyD88−/− mice) or aHSCs (α-SMA^MyD88−/− mice). MyD88 deficiency in qHSCs or aHSCs attenuated liver fibrosis in mice and inhibited α-SMA-positive cell activation. Inhibition of MyD88 in HSCs decreased α-SMA and collagen I levels, inflammatory cell infiltration, and pro-inflammatory gene expression. Furthermore, MyD88 signaling in HSCs increased the secretion of CXCL10, which promoted macrophage M1 polarization through CXCR3, leading to activation of the JAK/STAT1 pathway. Inhibition of CXCL10 attenuated macrophage M1 polarization and reduced liver fibrosis. Thus, MyD88 signaling in HSCs crucially contributes to liver fibrosis and provides a promising therapeutic target for the prevention and treatment of liver fibrosis.

The IL-18/IL-18R1 signalling axis: Diagnostic and therapeutic potential in hypertension and chronic kidney disease

Chronic kidney disease (CKD) is inherently an inflammatory condition, which ultimately results in the development of end stage renal disease or cardiovascular events. Low-grade inflammatory diseases such as hypertension and diabetes are leading causes of CKD. Declines in renal function correlate with elevated circulating pro-inflammatory cytokines in patients with these conditions. The inflammasome is an important inflammatory signalling platform that has been associated with low-grade chronic inflammatory diseases. Notably, activation and assembly of the inflammasome causes the auto cleavage of pro-caspase-1 into its active form, which then processes the pro-inflammatory cytokines pro-interleukin (IL)-1β and pro-IL-18 into their active forms. Currently, the nod-like receptor protein 3 (NLRP3) inflammasome has been implicated in the development of CKD in pre-clinical and clinical settings, and the ablation or inhibition of inflammasome components have been shown to be reno-protective in models of CKD. While clinical trials have demonstrated that neutralisation of IL-1β signalling by the drug anakinra lowers inflammation markers in haemodialysis patients, ongoing preclinical studies are showing that this ability to attenuate disease is limited in progressive models of kidney disease. These results suggest a potential predominant role for IL-18 in the development of CKD. This review will discuss the role of the inflammasome and its pro-inflammatory product IL-18 in the development of renal fibrosis and inflammation that contribute to the pathophysiology of CKD. Furthermore, we will examine the potential of the IL-18 signalling axis as an anti-inflammatory target in CKD and its usefulness as diagnostic biomarker to predict acute kidney injury.

Folic acid-mediated fibrosis is driven by C5a receptor 1-mediated activation of kidney myeloid cells

We previously reported that increased expression and activation of kidney cell complement components play an important role in the pathogenesis of renal scarring. Here we used floxed green fluorescent protein (GFP)-C5a receptor 1 (C5aR1) knock-in mice (GFP-C5ar1^fl/fl) and the model of Folic acid-induced kidney injury to define the cell types and potential mechanisms by which increased C5aR1 activation leads to fibrosis. Using flow cytometry and confocal microscopy we identified macrophages as the major interstitial cell type showing increased expression of C5aR1 in FA-treated mice. C5ar1^fl/fl.Lyz2Cre^+/- mice, in which C5aR1 has been specifically deleted in lysozyme M (LysM)-expressing myeloid cells, experienced reduced fibrosis when compared to control C5ar1^fl/fl mice. Examination of C5aR1-expressing macrophage transcriptomes by gene set enrichment analysis (GSEA) demonstrated that these cells were enriched in pathways corresponding to the complement cascade, collagen formation and the NABA matrisome, strongly pointing to their critical roles in tissue repair/scarring. Since C5aR1 was also detected in a small population of PDGFBR+ GFP+ cells we develop C5ar1^fl/fl.Foxd1Cre^+/- mice, in which C5aR1 is deleted specifically in pericytes, and found reduced FA-induced fibrosis. Primary cell cultures of platelet-derived growth factor receptor beta (PDGFRβ)+ pericytes isolated from FA-treated C5ar1^fl/fl.Foxd1Cre^+/- mice showed reduced secretion of several cytokines, including IL-6, and macrophage inflammatory proteins (MIP) 2, when compared to pericytes isolated from FA-treated control GFP-C5ar1^fl/fl mice. Collectively, these data imply that the C5a/C5aR1 axis activation primarily in interstitial cells contributes to the development of renal fibrosis.

Involvement of YTHDF1 in renal fibrosis progression via up-regulating YAP

Renal fibrosis is a progressive, fatal renal disease characterized by the aberrant accumulation of myofibroblasts that produce excess extracellular matrix (ECM) in the renal interstitium and glomeruli. Yes-associated protein (YAP) has been regarded as a crucial modulator in myofibroblast transformation, but its upstream regulator remains a mystery. In the present study investigating the participation of m6A methylation during renal fibrosis through bioinformatics analysis, we identified YTHDF1, a modulator of m6A methylation, as a key contributor for renal fibrosis because it was highly expressed in human fibrotic kidneys and had a significant correction with YAP. Their co-localization in human fibrotic kidneys was additionally shown by immunofluorescence. We then found that YTHDF1 was also up-regulated in fibrotic mouse kidneys induced by unilateral ureteral obstruction (UUO), high-dose folic acid administration, or the unilateral ischemia-reperfusion injury, further supporting a causal role of YTHDF1 during renal fibrosis. Consistent with this notion, YTHDF1 knockdown alleviated the progression of renal fibrosis both in cultured cells induced by transforming growth factor-beta administration and in the UUO mouse model. Meanwhile, YAP was accordingly down-regulated when YTHDF1 was inhibited. Furthermore, the specific binding of YTHDF1 to YAP mRNA was detected using RNA Binding Protein Immunoprecipitation, and the up-regulation of fibrotic related molecules in cultured cells induced by YTHDF1 over-expression plasmid was attenuated by YAP siRNA. Taken together, our data highlight the potential utility of YTHDF1 as an indicator for renal fibrosis and suggest that YTHDF1 inhibition might be a promising therapeutic strategy to alleviate renal fibrosis via downregulating YAP.

Assessing and counteracting fibrosis is a cornerstone of the treatment of CKD secondary to systemic and renal limited autoimmune disorders

Chronic kidney disease (CKD) is an increasing cause of morbidity and mortality worldwide. Besides the higher prevalence of diabetes, hypertension and aging worldwide, immune mediated disorders remain an important cause of kidney disease and are especially prevalent in young adults. Regardless of the initial insult, final pathway to CKD and kidney failure is always the loss of normal tissue and fibrosis development, in which the dynamic equilibrium between extracellular matrix synthesis and degradation is disturbed, leading to excessive production and accumulation. During fibrosis, a multitude of cell types intervene at different levels, but myofibroblasts and inflammatory cells are considered critical in the process. They exert their effects through different molecular pathways, of which transforming growth factor β (TGF-β) has demonstrated to be of particular importance. Additionally, CKD itself promotes fibrosis due to the accumulation of toxins and hormonal changes, and proteinuria is simultaneously a manifestation of CKD and a specific driver of renal fibrosis. Pathways involved in renal fibrosis and CKD are closely interrelated, and although important advances have been made in our knowledge of them, it is still necessary to translate them into clinical practice. Given the complexity of this process, it is highly likely that its treatment will require a multi-target strategy to control the origin of the damage but also the mechanisms that perpetuate it. Fortunately, rapid technology development over the last years and new available drugs in the nephrologist's armamentarium give reasons for optimism that more personalized assistance for CKD and renal fibrosis will appear in the future.

Upcoming treatments for morphea

Morphea (localized scleroderma) is a rare autoimmune connective tissue disease with variable clinical presentations, with an annual incidence of 0.4-2.7 cases per 100,000. Morphea occurs most frequently in children aged 2-14 years, and the disease exhibits a female predominance. Insights into morphea pathogenesis are often extrapolated from studies of systemic sclerosis due to their similar skin histopathologic features; however, clinically they are two distinct diseases as evidenced by different demographics, clinical features, disease course and prognosis. An interplay between genetic factors, epigenetic modifications, immune and vascular dysfunction, along with environmental hits are considered as the main contributors to morphea pathogenesis. In this review, we describe potential new therapies for morphea based on both preclinical evidence and ongoing clinical trials. We focus on different classes of therapeutics, including antifibrotic, anti-inflammatory, cellular and gene therapy, and antisenolytic approaches, and how these target different aspects of disease pathogenesis.

Total C-21 Steroidal Glycosides From Baishouwu Ameliorate Hepatic and Renal Fibrosis by Regulating IL-1β/MyD88 Inflammation Signaling

Fibrosis is a worldwide public health problem, which typically results from chronic diseases and often leads to organ malfunction. Chronic inflammation has been suggested to be the major trigger for fibrogenesis, yet mechanisms by which inflammatory signals drive fibrogenesis have not been fully elucidated. Total C-21 steroidal glycosides (TCSG) from Baishouwu are the main active components of the root of Cynanchum auriculatum Royle ex Wight, which exert hepatoprotective and anti-inflammation properties. In this study, we established a mouse model with the coexistence of hepatic and renal fibrosis and aimed to investigate the effects of TCSG from Baishouwu on fibrosis and explored the potential mechanisms. The results of biochemical and pathological examinations showed that TCSG from Baishouwu improved liver and kidney function and alleviated hepatic and renal fibrosis by reducing collagen and extracellular matrix deposition in bile duct ligation and unilateral ureteral occlusion (BDL&UUO) mice. According to network pharmacology analysis, the mechanisms underlying the effects of TCSG from Baishouwu on hepatic and renal fibrosis were associated with inflammatory response pathways, including “Signaling by interleukins”, “MAP kinase activation”, “MyD88 cascade initiated on plasma membrane”, and “Interleukin-1 family signaling”. Regression analysis and western blot results revealed that IL-1β/MyD88 inflammation signaling played an essential role in the anti-fibrotic effects of TCSG from Baishouwu. Further data displayed that TCSG from Baishouwu affected inflammatory response and extracellular matrix deposition via suppressing the activation of p38 MAPK/JNK and NF-κB p65 signaling cascades both in the liver and kidney of BDL&UUO mice. Thus, our findings suggest TCSG from Baishouwu as a natural regimen against hepatic and renal fibrosis and provide direct evidence that IL-1β/MyD88 signaling crucially contributes to hepatic and renal fibrosis and modulates liver-kidney crosstalk by maintaining tight control over inflammatory responses.

Fish oil replacement prevents, while docosahexaenoic acid-derived protectin DX mitigates end-stage-renal-disease in atherosclerotic diabetic mice

Diabetic nephropathy (DN) remains the major cause of end-stage renal disease (ESRD). We used high-fat/high-sucrose (HFHS)-fed LDLr^-/- /ApoB^100/100 mice with transgenic overexpression of IGFII in pancreatic β-cells (LRKOB100/IGFII) as a model of ESRD to test whether dietary long chain omega-3 polyunsaturated fatty acids LCω3FA-rich fish oil (FO) could prevent ESRD development. We further evaluated the potential of docosahexaenoic acid (DHA)-derived pro-resolving lipid mediators, 17-hydroxy-DHA (17-HDHA) and Protectin DX (PDX), to reverse established ESRD damage. HFHS-fed vehicle-treated LRKOB100/IGFII mice developed severe kidney dysfunction leading to ESRD, as revealed by advanced glomerular fibrosis and mesangial expansion along with reduced percent survival. The kidney failure outcome was associated with cardiac dysfunction, revealed by reduced heart rate and prolonged diastolic and systolic time. Dietary FO prevented kidney damage, lean mass loss, cardiac dysfunction, and death. 17-HDHA reduced podocyte foot process effacement while PDX treatment alleviated kidney fibrosis and mesangial expansion as compared to vehicle treatment. Only PDX therapy was effective at preserving the heart function and survival rate. These results show that dietary LCω3FA intake can prevent ESRD and cardiac dysfunction in LRKOB100/IGFII diabetic mice. Our data further reveals that PDX can protect against renal failure and cardiac dysfunction, offering a potential new therapeutic strategy against ESRD.

Lung Pericytes in Pulmonary Vascular Physiology and Pathophysiology

Pericytes are mesenchymal-derived mural cells localized within the basement membrane of pulmonary and systemic capillaries. Besides structural support, pericytes control vascular tone, produce extracellular matrix components, and cytokines responsible for promoting vascular homeostasis and angiogenesis. However, pericytes can also contribute to vascular pathology through the production of pro-inflammatory and pro-fibrotic cytokines, differentiation into myofibroblast-like cells, destruction of the extracellular matrix, and dissociation from the vessel wall. In the lung, pericytes are responsible for maintaining the integrity of the alveolar-capillary membrane and coordinating vascular repair in response to injury. Loss of pericyte communication with alveolar capillaries and a switch to a pro-inflammatory/pro-fibrotic phenotype are common features of lung disorders associated with vascular remodeling, inflammation, and fibrosis. In this article, we will address how to differentiate pericytes from other cells, discuss the molecular mechanisms that regulate the interactions of pericytes and endothelial cells in the pulmonary circulation, and the experimental tools currently used to study pericyte biology both in vivo and in vitro. We will also discuss evidence that links pericytes to the pathogenesis of clinically relevant lung disorders such as pulmonary hypertension, idiopathic lung fibrosis, sepsis, and SARS-COVID. Future studies dissecting the complex interactions of pericytes with other pulmonary cell populations will likely reveal critical insights into the origin of pulmonary diseases and offer opportunities to develop novel therapeutics to treat patients afflicted with these devastating disorders. © 2021 American Physiological Society. Compr Physiol 11:2227-2247, 2021.

Separated parabiont reveals the fate and lifespan of peripheral-derived immune cells in normal and ischaemia-induced injured kidneys

Immune cell infiltration plays a key role in acute kidney injury (AKI) to chronic kidney disease (CKD) progression. T lymphocytes, neutrophils, monocytes/macrophages and other immune cells regulate inflammation, tissue remodelling and repair. To determine the kinetics of accumulation of various immune cell populations, we established an animal model combining parabiosis and separation surgery to explore the fate and lifespan of peripheral leucocytes that migrate to the kidney. We found that peripheral T lymphocytes could survive for a long time (more than 14 days), whereas peripheral neutrophils survived for a short time in both healthy and ischaemia-induced damaged kidneys. Nearly half of the peripheral-derived macrophages disappeared after 14 days in normal kidneys, while their existing time in the inflammatory kidneys was prolonged. A fraction of F4/80^high macrophages were renewed from the circulating monocyte pool. In addition, we found that after renal ischaemia reperfusion, neutrophils increased significantly in the early phase, and T lymphocytes mainly accumulated in the late stage, whereas macrophages infiltrated throughout AKI-CKD progression and were sustained longer in injured as opposed to normal kidneys. In conclusion, peripheral-derived macrophages, T lymphocytes and neutrophils exhibit different lifespans in the kidney, which may play different roles during AKI-CKD progression.

Shen Shuai II Recipe Attenuates Renal Interstitial Fibrosis by Improving Hypoxia via the IL-1β/c-Myc Pathway

Background

Renal interstitial fibrosis is a pathological manifestation of progression of chronic kidney disease induced by various factors. Shen Shuai II Recipe (SSR) has been used in clinical practice for more than 20 years, and clinical studies have confirmed that SSR significantly improves the renal function of patients with chronic kidney disease. However, the specific mechanisms underlying its efficacy require further research. This study aims to explore the influencing factors of renal interstitial fibrosis in the context of hypoxia via the IL-1β/c-Myc pathway and the potential molecular mechanisms of SSR intervention in vivo and in vitro.

Methods

A rat model of chronic renal failure was developed by performing 5/6 (ablation/infarction, A/I) surgery on randomly selected, male Sprague Dawley rats. Thirty-six successfully modeled rats were randomly divided into three groups: 5/6 (A/I), 5/6 (A/I) + SSR, and 5/6 (A/I) + losartan. Another 12 rats were used as the sham group. After 8 weeks of the corresponding intervention, renal function, liver function, and protein expression of renal-fibrosis-related factors, HIF-1α, IL-1β, and c-Myc, were detected. In vitro analysis was performed using hypoxia-induced rat renal tubular epithelial cells (NRK-52E) and IL-1β-stimulated rat renal interstitial fibroblasts (NRK-49F). IL-1β concentration in the culture medium and IL-1β protein expression in hypoxic NRK-52E treated with different concentrations of SSR were investigated. Furthermore, we also studied the changes in protein expression of c-Myc and fibrosis-related factors after c-Myc gene silencing in IL-1β-stimulated NRK-49F treated with SSR.

Results

Shen Shuai II Recipe significantly reduced RIF and downregulated the expression of HIF-1α, c-Myc, and IL-1β proteins in 5/6 (A/I) rats with chronic renal failure. It also inhibited IL-1β secretion from NRK-52E induced by hypoxia, which in turn inhibited fibroblast activation mediated by the IL-1β/c-Myc pathway, and finally reduced the overproduction of the extracellular matrix.

Conclusion

The renoprotective effects of SSR in rats with chronic renal failure may be related to its inhibition of hypoxia via the IL-1β/c-Myc pathway. Thus, SSR is a potentially effective drug for delaying the progression of renal interstitial fibrosis.

Alarmin-activated B cells accelerate murine atherosclerosis after myocardial infarction via plasma cell-immunoglobulin-dependent mechanisms

AIMS

Myocardial infarction (MI) accelerates atherosclerosis and greatly increases the risk of recurrent cardiovascular events for many years, in particular, strokes and MIs. Because B cell-derived autoantibodies produced in response to MI also persist for years, we investigated the role of B cells in adaptive immune responses to MI.

METHODS AND RESULTS

We used an apolipoprotein-E-deficient (ApoE-/-) mouse model of MI-accelerated atherosclerosis to assess the importance of B cells. One week after inducing MI in atherosclerotic mice, we depleted B cells using an anti-CD20 antibody. This treatment prevented subsequent immunoglobulin G accumulation in plaques and MI-induced accelerated atherosclerosis. In gain of function experiments, we purified spleen B cells from mice 1 week after inducing MI and transferred these cells into atherosclerotic ApoE-/- mice, which greatly increased immunoglobulin G (IgG) accumulation in plaque and accelerated atherosclerosis. These B cells expressed many cytokines that promote humoural immunity and in addition, they formed germinal centres within the spleen where they differentiated into antibody-producing plasma cells. Specifically deleting Blimp-1 in B cells, the transcriptional regulator that drives their terminal differentiation into antibody-producing plasma cells prevented MI-accelerated atherosclerosis. Alarmins released from infarcted hearts were responsible for activating B cells via toll-like receptors and deleting MyD88, the canonical adaptor protein for inflammatory signalling downstream of toll-like receptors, prevented B-cell activation and MI-accelerated atherosclerosis.

CONCLUSION

Our data implicate early B-cell activation and autoantibodies as a central cause for accelerated atherosclerosis post-MI and identifies novel therapeutic strategies towards preventing recurrent cardiovascular events such as MI and stroke.

Small molecules against the origin and activation of myofibroblast for renal interstitial fibrosis therapy

Renal interstitial fibrosis (RIF) is a common pathological response in a broad range of prevalent chronic kidney diseases and ultimately leads to renal failure and death. Although RIF causes a high morbi-mortality worldwide, effective therapeutic drugs are urgently needed. Myofibroblasts are identified as the main effector during the process of RIF. Multiple types of cells, including fibroblasts, epithelial cells, endothelial cells, macrophages and pericytes, contribute to renal myofibroblasts origin, and lots of mediators, including signaling pathways (Transforming growth factor-β1, mammalian target of rapamycin and reactive oxygen species) and epigenetic modifications (Histone acetylation, microRNA and long non-coding RNA) are participated in renal myofibroblasts activation during renal fibrogenesis, suggesting that these mediators may be the promising targets for treating RIF. In addition, many small molecules show profound therapeutic effects on RIF by suppressing the origin and activation of renal myofibroblasts. Taken together, the review focuses on the mechanisms of the origin and activation of renal myofibroblasts in RIF and the small molecules against them improving RIF, which will provide a new insight for RIF therapy.

Fibroblast heterogeneity and tertiary lymphoid tissues in the kidney

Fibroblasts reside in various organs and support tissue structure and homeostasis under physiological conditions. Phenotypic alterations of fibroblasts underlie the development of diverse pathological conditions, including organ fibrosis. Recent advances in single‐cell biology have revealed that fibroblasts comprise heterogeneous subpopulations with distinct phenotypes, which exert both beneficial and detrimental effects on the host organs in a context‐dependent manner. In the kidney, phenotypic alterations of resident fibroblasts provoke common pathological conditions of chronic kidney disease (CKD), such as renal anemia and peritubular capillary loss. Additionally, in aged injured kidneys, fibroblasts provide functional and structural supports for tertiary lymphoid tissues (TLTs), which serve as the ectopic site of acquired immune reactions in various clinical contexts. TLTs are closely associated with aging and CKD progression, and the developmental stages of TLTs reflect the severity of renal injury. In this review, we describe the current understanding of fibroblast heterogeneity both under physiological and pathological conditions, with special emphasis on fibroblast contribution to TLT formation in the kidney. Dissecting the heterogeneous characteristics of fibroblasts will provide a promising therapeutic option for fibroblast‐related pathological conditions, including TLT formation.

Applications of biomaterials for immunosuppression in tissue repair and regeneration

The immune system plays an essential role in tissue repair and regeneration. Regardless of innate or adaptive immune responses, immunosuppressive strategies such as macrophage polarization and regulatory T (Treg) cell induction can be used to modulate the immune system to promote tissue repair and regeneration. Biomaterials can improve the production of anti-inflammatory macrophages and Treg cells by providing physiochemical cues or delivering therapeutics such as cytokines, small molecules, microRNA, growth factors, or stem cells in the damaged tissues. Herein, we present an overview of immunosuppressive modulation by biomaterials in tissue regeneration and highlight the mechanisms of macrophage polarization and Treg cell induction. Overall, we foresee that future biomaterials for regenerative strategies will entail more interactions between biomaterials and the immune cells, and more mechanisms of immunosuppression related to T cell subsets remain to be discovered and applied to develop novel biomaterials for tissue repair and regeneration. STATEMENT OF SIGNIFICANCE: Immunosuppression plays a key role in tissue repair and regeneration, and biomaterials can interact with the immune system through their biological properties and by providing physiochemical cues. Here, we summarize the studies on biomaterials that have been used for immunosuppression to facilitate tissue regeneration. In the first part of this review, we demonstrate the crucial role of macrophage polarization and induction of T regulatory (Treg) cells in immunosuppression. In the second part, distinct approaches used by biomaterials to induce immunosuppression are introduced, which show excellent performance in terms of promoting tissue regeneration.

Temporal and Spatial Dynamics of Inflammasome Activation After Ischemic Stroke

Background: The inflammasome represents a highly pro-inflammatory mechanism. It has been identified that inflammasome was activated after ischemic stroke. However, the impact of inflammasomes on stroke outcomes remains contradictory. The participating molecules and the functioning arena of post-stroke inflammasome activation are still elusive.

Methods: In the present study, blood samples from stroke patients were collected and analyzed with flow cytometry to evaluate the correlation of inflammasome activation and stroke outcomes. A stroke model was established using male C57/Bl6 mice with transient middle cerebral artery occlusion (tMCAO, 1 h). The dynamics of inflammasome components, cell type, and location of inflammasome activation and the therapeutic effects of inhibiting post-stroke inflammasome executors were evaluated.

Results: We found that a high level of inflammasome activation might indicate detrimental stroke outcomes in patients and mice models. Post-stroke inflammasome activation, especially NLRP3, cleaved Caspase-1, cleaved Caspase-11, IL-1β, IL-18, and GSDMD, peaked at 3–5 days and declined at 7 days with the participation of multiple components in mice. Macrophage that infiltrated into the ischemic lesion was the main arena for post-stroke inflammasome activation among myeloid cells according to the data of mice. Among all the members of the Caspase family, Caspase-1 and −11 served as the main executing enzymes. Inhibiting Caspase-1/−11 signaling efficiently suppressed DAMPs-induced macrophage inflammasome activation and displayed neuroprotection to stroke models including infarct size (Control: 48.05 ± 14.98; Cas1.i: 19.34 ± 12.21; Cas11.i: 21.43 ± 14.67, P < 0.001) and neurological deficit score (0 d-Control: 2.20 ± 0.63; 0 d-Cas1.i: 2.20 ± 0.63; 0 d-Cas11.i: 2.20 ± 0.63; 1 d-Control: 2.50 ± 0.53; 1 d-Cas1.i: 1.50 ± 0.71; 1 d-Cas11.i: 2.00 ± 0.67; 2 d-Control: 2.30 ± 0.48; 2 d-Cas1.i: 1.30 ± 0.48; 2 d-Cas11.i: 1.50 ± 0.53; 3 d-Control: 2.00 ± 0.67; 3 d-Cas1.i: 1.20 ± 0.42; 3 d-Cas11.i: 1.30 ± 0.48, P < 0.001).

Conclusions: Taken together, inflammasome activation played a detrimental role in stroke pathology. Targeting post-stroke inflammasome executing enzymes fitting in the dynamics of macrophages might obtain potential and efficient therapeutic effects.

Pericyte-like cells undergo transcriptional reprogramming and distinct functional adaptations in acute lung injury

We previously reported on the role of pericyte-like cells as functional sentinel immune cells in lung injury. However, much about the biological role of pericytes in lung injury remains unknown. Lung pericyte-like cells are well-positioned to sense disruption to the epithelial barrier and coordinate local inflammatory responses due to their anatomic niche within the alveoli. In this report, we characterized transcriptional responses and functional changes in pericyte-like cells following activation by alveolar components from injured and uninjured lungs in a mouse model of acute lung injury (ALI). Purified pericyte-like cells from lung digests using PDGFRβ as a selection marker were expanded in culture as previously described (1). We induced sterile acute lung injury in mice with recombinant human Fas ligand (rhFasL) instillation followed by mechanical ventilation (1). We then collected bronchoalveolar lavage fluid (BALF) from injured and uninjured mice. Purified pericyte-like cells in culture were exposed to growth media only (control), BALF from uninjured mice, and BALF from injured mice for 6 and 24 hours. RNA collected from these treatment conditions were processed for RNAseq. Targets of interest identified by pathway analysis were validated using in vitro and in vivo assays. We observed robust global transcriptional changes in pericyte-like cells following treatment with uninjured and injured BALF at 6 hours, but this response persisted for 24 hours only after exposure to injured BALF. Functional enrichment analysis of pericytes treated with injured BALF revealed the activation of pro-inflammatory, cell migration, and angiogenesis-related pathways, whereas processes associated with tissue development and cell differentiation were down-regulated. We validated select upregulated targets in the inflammatory, angiogenic, and cell migratory pathways using functional biological assays in vitro and in vivo. We conclude that lung pericyte-like cells are highly responsive to alveolar compartment content from both uninjured and injured lungs, but injured BALF elicits a more sustained response. The inflammatory, angiogenic, and migratory changes exhibited by activated pericyte-like cells underscore the phenotypic plasticity of these specialized stromal cells in the setting of acute lung injury.

PMMA-Based Continuous Hemofiltration Modulated Complement Activation and Renal Dysfunction in LPS-Induced Acute Kidney Injury

Sepsis-induced acute kidney injury (AKI) is a frequent complication in critically ill patients, refractory to conventional treatments. Aberrant activation of innate immune system may affect organ damage with poor prognosis for septic patients. Here, we investigated the efficacy of polymethyl methacrylate membrane (PMMA)-based continuous hemofiltration (CVVH) in modulating systemic and tissue immune activation in a swine model of LPS-induced AKI. After 3 h from LPS infusion, animals underwent to PMMA-CVVH or polysulfone (PS)-CVVH. Renal deposition of terminal complement mediator C5b-9 and of Pentraxin-3 (PTX3) deposits were evaluated on biopsies whereas systemic Complement activation was assessed by ELISA assay. Gene expression profile was performed from isolated peripheral blood mononuclear cells (PBMC) by microarrays and the results validated by Real-time PCR. Endotoxemic pigs presented oliguric AKI with increased tubulo-interstitial infiltrate, extensive collagen deposition, and glomerular thrombi; local PTX-3 and C5b-9 renal deposits and increased serum activation of classical and alternative Complement pathways were found in endotoxemic animals. PMMA-CVVH treatment significantly reduced tissue and systemic Complement activation limiting renal damage and fibrosis. By microarray analysis, we identified 711 and 913 differentially expressed genes with a fold change >2 and a false discovery rate <0.05 in endotoxemic pigs and PMMA-CVVH treated-animals, respectively. The most modulated genes were Granzyme B, Complement Factor B, Complement Component 4 Binding Protein Alpha, IL-12, and SERPINB-1 that were closely related to sepsis-induced immunological process. Our data suggest that PMMA-based CVVH can efficiently modulate immunological dysfunction in LPS-induced AKI.

3-Bromopyruvate decreased kidney fibrosis and fibroblast activation by suppressing aerobic glycolysis in unilateral ureteral obstruction mice model

AIMS

Enhanced aerobic glycolysis is a motivation of fibroblast-myofibroblast transdifferentiation (FMT), leading to kidney fibrosis. 3-Bromopyruvate (3-BrPA) is a glycolysis inhibitor and has fibrosis-protected effect in liver. This study aims to explore the effects of 3-BrPA on aerobic glycolysis and kidney fibrosis in a unilateral ureteral obstruction (UUO) mice model and transforming growth factor-β1(TGF-β1)-stimulated normal rat kidney fibroblast (NRK49F) cell model in vitro.

MAIN METHODS

In vivo UUO mouse model and in vitro TGF-β1 stimulated cell model were built. Immunohistochemical staining, Western blots, Real-time PCR and fluorescence microscopy were employed to detect extra cellular matrix (ECM) synthesis, fibroblast activation, aerobic glycolysis switch and related signaling pathways.

KEY FINDINGS

HE and Masson's Trichrome staining showed that 3-BrPA substantially suppressed kidney injury and interstitial collagen production. 3-BrPA also attenuated ECM accumulation in a dose-dependent manner, as shown by immunohistochemistry staining, RT-PCR and western blot. Furthermore, 3-BrPA inhibited FMT, as indicated by α-SMA and PCNA immunofluorescence double staining. Additionally, the results of MTT assay indicated 3-BrPA prevented TGF-β1 induced fibroblasts proliferation in a time- and dose-dependent manner. Mechanistically, molecular docking results showed that 3-BrPA effectively decreased the aerobic glycolysis related enzymes Hexokinase-2 (HK-2), Lactate dehydrogenase A (LDHA) and Pyruvate kinase isozymes M2 (PKM-2), as well as inhibited IL-1 receptor-associated kinase 4 (IRAK4)/MYC protein levels.

SIGNIFICANCE

Our study highlighted that 3-BrPA is a potential reno-protective agent in kidney fibrosis through the inhibition of fibroblasts aerobic glycolysis might via IRAK4/MYC signal pathways.

Genetics and Pathogenetic Role of Inflammasomes in Philadelphia Negative Chronic Myeloproliferative Neoplasms: A Narrative Review

The last decade has been very important for the quantity of preclinical information obtained regarding chronic myeloproliferative neoplasms (MPNs) and the following will be dedicated to the translational implications of the new biological acquisitions. The overcoming of the mechanistic model of clonal evolution and the entry of chronic inflammation and dysimmunity into the new model are the elements on which to base a part of future therapeutic strategies. The innate immune system plays a major role in this context. Protagonists of the initiation and regulation of many pathological aspects, from cytokine storms to fibrosis, the NLRP3 and AIM2 inflammasomes guide and condition the natural history of the disease. For this reason, MPNs share many biological and clinical aspects with non-neoplastic diseases, such as autoimmune disorders. Finally, cardiovascular risk and disturbances in iron metabolism and myelopoiesis are also closely linked to the role of inflammasomes. Although targeted therapies are already being tested, an increase in knowledge on the subject is desirable and potentially translates into better care for patients with MPNs.

The Role of Vascular Cells in Pancreatic Beta-Cell Function

Insulin-producing β-cells constitute the majority of the cells in the pancreatic islets. Dysfunction of these cells is a key factor in the loss of glucose regulation that characterizes type 2 diabetes. The regulation of many of the functions of β-cells relies on their close interaction with the intra-islet microvasculature, comprised of endothelial cells and pericytes. In addition to providing islet blood supply, cells of the islet vasculature directly regulate β-cell activity through the secretion of growth factors and other molecules. These factors come from capillary mural pericytes and endothelial cells, and have been shown to promote insulin gene expression, insulin secretion, and β-cell proliferation. This review focuses on the intimate crosstalk of the vascular cells and β-cells and its role in glucose homeostasis and diabetes.

Fibrosis: from mechanisms to medicines

Fibrosis can affect any organ and is responsible for up to 45% of all deaths in the industrialized world. It has long been thought to be relentlessly progressive and irreversible, but both preclinical models and clinical trials in various organ systems have shown that fibrosis is a highly dynamic process. This has clear implications for therapeutic interventions that are designed to capitalize on this inherent plasticity. However, despite substantial progress in our understanding of the pathobiology of fibrosis, a translational gap remains between the identification of putative antifibrotic targets and conversion of this knowledge into effective treatments in humans. Here we discuss the transformative experimental strategies that are being leveraged to dissect the key cellular and molecular mechanisms that regulate fibrosis, and the translational approaches that are enabling the emergence of precision medicine-based therapies for patients with fibrosis.

Are Migraine Patients at Increased Risk for Symptomatic Coronavirus Disease 2019 Due to Shared Comorbidities?

The coronavirus disease 2019 (COVID-19) pandemic has rapidly transformed the whole world and forced us to look through comorbid diseases and risk factors from a different perspective. COVID-19 shows some inherent risk factors like cardiovascular comorbidities independent from age, gender, and geographic location. One of the most peculiar features of the COVID-19 pandemic is that severe acute respiratory syndrome coronavirus 2 respiratory infections disproportionately impact patients with hypertension, diabetes, and other cardiovascular comorbidities rather than those with allergic respiratory diseases and immune-compromised conditions. Migraine is a complex neuro-vasculo-inflammatory disorder that is also packed frequently with certain medical conditions including vascular disorders, hypertension, allergic diseases such as asthma and systemic inflammatory disorders. Accordingly, 2 different questions arise during the pandemic: (1) Do share comorbidities of cardiovascular diseases and hypertension increase the risk of symptomatic COVID-19 for migraine patients? (2) Do comorbid allergic and atopic diseases, including asthma act as opposite influencers alongside with female gender? This paper focuses on the co-existence of comorbidities of COVID-19, in comparison with migraine, based on a wide clinical dataset and available reports. Discussed mechanisms include potential strategic roles of angiotensin-converting enzyme 2, angiotensin-II, and nucleotide oligomerization domain-like receptor family, pyrin domain containing 3 inflammasome, playing remarkable parts in the pathogenesis of COVID-19 and migraine. There are also some clues about the importance of endothelial and pericyte dysfunction and neuroinflammation in COVID-19 infection, related to complications and survival of the patients. The large epidemiological studies as well as basic research, focusing on migraine patients with COVID-19 will clarify these vital questions during the upcoming periods.

Mitochondrial dysfunction and the AKI-to-CKD transition

Acute kidney injury (AKI) has been widely recognized as an important risk factor for the occurrence and development of chronic kidney disease (CKD). Even milder AKI has adverse consequences and could progress to renal fibrosis, which is the ultimate common pathway for various terminal kidney diseases. Thus, it is urgent to develop a strategy to hinder the transition from AKI to CKD. Some mechanisms of the AKI-to-CKD transition have been revealed, such as nephron loss, cell cycle arrest, persistent inflammation, endothelial injury with vascular rarefaction, and epigenetic changes. Previous studies have elucidated the pivotal role of mitochondria in acute injuries and demonstrated that the fitness of this organelle is a major determinant in both the pathogenesis and recovery of organ function. Recent research has suggested that damage to mitochondrial function in early AKI is a crucial factor leading to tubular injury and persistent renal insufficiency. Dysregulation of mitochondrial homeostasis, alterations in bioenergetics, and organelle stress cross talk contribute to the AKI-to-CKD transition. In this review, we focus on the pathophysiology of mitochondria in renal recovery after AKI and progression to CKD, confirming that targeting mitochondria represents a potentially effective therapeutic strategy for the progression of AKI to CKD.

Double Labeling of PDGFR-β and α-SMA in Swine Models of Acute Kidney Injury to Detect Pericyte-to-Myofibroblast Transdifferentation as Early Marker of Fibrosis

Growing evidences suggest that peritubular capillaries pericytes are the main source of scar-forming myofibroblasts during chronic kidney disease (CKD), as well as early phases of acute kidney injury (AKI). In a swine model of sepsis and I/R (Ischemia Reperfusion) injury-induced AKI we demonstrated that renal pericytes are able to transdifferentiate toward α-SMA⁺ myofibroblasts leading to interstitial fibrosis. Even if precise pericytes identification requires transmission electron microscopy and the co-immunostaining of several markers (i.e., Gli, NG2 chondroitin sulphate proteoglycan, CD146, desmin or CD73) and emerging new markers (CD248 or TEM1, endosialin), previous studies suggested that PDGFR-β could be used as marker for renal pericytes characterization. Recently, double immunofluorescence staining of PDGFR-β and α-SMA was performed to identify the damage activated pericytes (PDGFR-β⁺/α-SMA⁺ cells) in the early phase of fibrosis development. Our data highlighted the crucial role of renal pericytes in the physiopathology of sepsis and I/R associated AKI. In this protocol, we describe the procedure for double immunofluorescence staining of PDGFR-β and α-SMA in swine Formalin-Fixed Paraffin-Embedded (FFPE) kidney biopsies and the method for image analysis and quantification.

Interleukin-36 Cytokine/Receptor Signaling: A New Target for Tissue Fibrosis

Tissue fibrosis is a major unresolved medical problem, which impairs the function of various systems. The molecular mechanisms involved are poorly understood, which hinders the development of effective therapeutic strategies. Emerging evidence from recent studies indicates that interleukin 36 (IL-36) and the corresponding receptor (IL-36R), a newly-characterized cytokine/receptor signaling complex involved in immune-inflammation, play an important role in the pathogenesis of fibrosis in multiple tissues. This review focuses on recent experimental findings, which implicate IL-36R and its associated cytokines in different forms of organ fibrosis. Specifically, it outlines the molecular basis and biological function of IL-36R in normal cells and sums up the pathological role in the development of fibrosis in the lung, kidney, heart, intestine, and pancreas. We also summarize the new progress in the IL-36/IL-36R-related mechanisms involved in tissue fibrosis and enclose the potential of IL-36R inhibition as a therapeutic strategy to combat pro-fibrotic pathologies. Given its high association with disease, gaining new insight into the immuno-mechanisms that contribute to tissue fibrosis could have a significant impact on human health.

NLRP3 Is Involved in the Maintenance of Cerebral Pericytes

Pericytes play a central role in regulating the structure and function of capillaries in the brain. However, molecular mechanisms that drive pericyte proliferation and differentiation are unclear. In our study, we immunostained NACHT, LRR and PYD domains-containing protein 3 (NLRP3)-deficient and wild-type littermate mice and observed that NLRP3 deficiency reduced platelet-derived growth factor receptor β (PDGFRβ)-positive pericytes and collagen type IV immunoreactive vasculature in the brain. In Western blot analysis, PDGFRβ and CD13 proteins in isolated cerebral microvessels from the NLRP3-deficient mouse brain were decreased. We further treated cultured pericytes with NLRP3 inhibitor, MCC950, and demonstrated that NLRP3 inhibition attenuated cell proliferation but did not induce apoptosis. NLRP3 inhibition also decreased protein levels of PDGFRβ and CD13 in cultured pericytes. On the contrary, treatments with IL-1β, the major product of NLRP3-contained inflammasome, increased protein levels of PDGFRβ, and CD13 in cultured cells. The alteration of PDGFRβ and CD13 protein levels were correlated with the phosphorylation of AKT. Inhibition of AKT reduced both protein markers and abolished the effect of IL-1β activation in cultured pericytes. Thus, NLRP3 activation might be essential to maintain pericytes in the healthy brain through phosphorylating AKT. The potential adverse effects on the cerebral vascular pericytes should be considered in clinical therapies with NLRP3 inhibitors.

Central IRAK-4 kinase inhibition for the treatment of pain following nerve injury in rats

There is ample evidence for the role of the immune system in developing chronic pain following peripheral nerve injury. Especially Toll-like receptors (TLRs) and their associated signaling components and pro-inflammatory cytokines such as IL-1β, induced after injury, are involved in nociceptive processes and believed to contribute to the manifestation of chronic neuropathic pain states. Whereas the inhibition of the kinase function of IRAK-4, a central kinase downstream of TLRs and IL-1 receptors (IL-1Rs), seems efficacious in various chronic inflammatory and autoimmune models, it's role in regulating chronic neuropathic pain remained elusive to date. Here, we examined whether pharmacological inhibition of IRAK-4 kinase activity using PF-06650833 and BMS-986147, two clinical-stage kinase inhibitors, is effective for controlling persistent pain following nerve injury. Both inhibitors potently inhibited TLR-triggered cytokine release in human peripheral blood mononuclear cell (PBMC) as well as human and rat whole blood cultures. BMS-986147 showing favorable pharmacokinetic (PK) properties, significantly inhibited R848-triggered plasma TNF levels in a rat in vivo cytokine release model after single oral dosing. However, BMS-986147 dose dependently reversed cold allodynia in a rat chronic constriction injury (CCI) model following intrathecal administration only, supporting the notion that central neuro-immune modulation is beneficial for treating chronic neuropathic pain. Although both inhibitors were efficacious in inhibiting IL-1β- or TLR-triggered cytokine release in rat dorsal root ganglion cultures, only partial efficacy was reached in IL-1β-stimulated human glial cultures indicating that inhibiting IRAK-4́'s kinase function might be partially dispensable for human IL-1β driven neuroinflammation. Overall, our data demonstrate that IRAK-4 inhibitors could provide therapeutic benefit in chronic pain following nerve injury, and the central driver for efficacy in the neuropathic pain model as well as potential side effects of centrally available IRAK-4 inhibitors warrant further investigation to develop effective analgesia for patients in high unmet medical need.

Mesenchymal perivascular cells in immunity and disease

The mesenchymal microenvironment is increasingly recognized as a major player in immunity. Here we focus on mesenchymal cells located within or in proximity to the blood vessels wall, which include pericytes, adventitial fibroblasts and mesenchymal stromal cells. We discuss recent evidence that these cells play a role in tissue homeostasis, immunity and inflammatory pathologies by multiple mechanisms, including vascular modulation, leucocyte migration, activation or survival in the perivascular space and differentiation into specialized 'effector' mesenchymal cells essential for tissue repair and immunity, such as myofibroblasts and lymphoid stromal cells. When dysregulated, these responses contribute to inflammatory and fibrotic diseases.