Endothelial NF-κB Blockade Abrogates ANCA-Induced GN

The role of transcription factors in the pathogenesis and therapeutic targeting of vascular diseases

Transcription factors (TFs) constitute an essential component of epigenetic regulation. They contribute to the progression of vascular diseases by regulating epigenetic gene expression in several vascular diseases. Recently, numerous regulatory mechanisms related to vascular pathology, ranging from general TFs that are continuously activated to histiocyte-specific TFs that are activated under specific circumstances, have been studied. TFs participate in the progression of vascular-related diseases by epigenetically regulating vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs). The Krüppel-like family (KLF) TF family is widely recognized as the foremost regulator of vascular diseases. KLF11 prevents aneurysm progression by inhibiting the apoptosis of VSMCs and enhancing their contractile function. The presence of KLF4, another crucial member, suppresses the progression of atherosclerosis (AS) and pulmonary hypertension by attenuating the formation of VSMCs-derived foam cells, ameliorating endothelial dysfunction, and inducing vasodilatory effects. However, the mechanism underlying the regulation of the progression of vascular-related diseases by TFs has remained elusive. The present study categorized the TFs involved in vascular diseases and their regulatory mechanisms to shed light on the potential pathogenesis of vascular diseases, and provide novel insights into their diagnosis and treatment.

Toll-like receptor signaling pathway involved in pathogenesis of thromboangiitis obliterans through activating of NF-κB

OBJECTIVES

The pathogenic mechanisms of Thromboangiitis Obliterans (TAO) are not entirely known and autoimmune inflammation plays a vital role in the initiation and continuance of TAO activity. The authors investigated in this study the role of the TLR signaling pathway in the pathogenesis of TAO.

METHODS

First, the authors detected the expressions of MyD88, TRIF and NF-κB in vascular walls of 46 patients with TAO and 32 patients with trauma and osteosarcoma by western blot assay. Second, the authors detected the cellular localization of MyD88, TRIF and NF-κB in vascular walls of patients with TAO by immunofluorescent assay.

RESULTS

The protein expressions of MyD88, TRIF and NF-κB were much higher in vascular walls of TAO patients (p < 0.05). Higher expressions of MyD88 and NF-κB were detected both on vascular endothelial and vascular smooth muscle cells of TAO patients. However, higher expression of TRIF was just detected on vascular smooth muscle cells of TAO patients.

CONCLUSIONS

These dates suggest that the TLR signaling pathway might play an important role in the pathogenesis of TAO, it might induce vasospasm, vasculitis and thrombogenesis to lead to the pathogenesis and progression of TAO.

MC3/SAINT-O-Somes, a novel liposomal delivery system for efficient and safe delivery of siRNA into endothelial cells

Increased understanding of chronic inflammatory diseases and the role of endothelial cell (EC) activation herein, have urged interest in sophisticated strategies to therapeutically intervene in activated EC to treat these diseases. Liposome-mediated delivery of therapeutic siRNA in inflammation-activated EC is such a strategy. In this study, we describe the design and characterisation of two liposomal siRNA delivery systems formulated with the cationic MC3 lipid or MC3/SAINT mixed lipids, referred to as MC3-O-Somes (MOS) and MC3/SAINT-O-Somes (MSS). The two formulations showed comparable physicochemical properties, except for better siRNA encapsulation efficiency in the MSS formulation. Antibody-mediated VCAM-1 targeting (AbVCAM-1) increased the association of the targeted MOS and MSS with activated EC, although the targeted MOS showed a significantly higher VCAM-1 specific association than the targeted MSS. AbVCAM-1 MSS containing RelA siRNA achieved significant downregulation of RelA expression, while AbVCAM-1 MOS containing RelA siRNA did not downregulate RelA expression in activated EC. Additionally, AbVCAM-1 MSS containing RelA siRNA showed low cytotoxicity in EC and at the same time prohibited endothelial inflammatory activation by reducing expression of cell adhesion molecules. The AbVCAM-1 MSS formulation is a novel siRNA delivery system based on a combination of the cationic lipids MC3 and SAINT, that shows good physicochemical characteristics, enhanced endothelial cell association, improved transfection activity, low toxicity and significant anti-inflammatory effect, thereby complying with the requirements for future in vivo investigations.

Animal models for anti-neutrophil cytoplasmic antibody-associated vasculitis: Are current models good enough?

Antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) is a rare and severe systemic autoimmune disease characterized by pauci-immune necrotizing inflammation of small blood vessels. AAV involves multiple organ systems throughout the body. Our knowledge of the pathogenesis of AAV has increased considerably in recent years, involving cellular, molecular and genetic factors. Because of the controlled environment with no other confounding factors, animal models are beneficial for studying the mechanistic details of disease development and for providing novel therapeutic targets with fewer toxic side effects. However, the complexity and heterogeneity of AAV make it very difficult to establish a single animal model that can fully represent the entire clinical spectrum found in patients. The aim of this review is to overview the current status of animal models for AAV, outline the pros and cons of methods, and propose potential directions for future research.

Differential effects of oleate on vascular endothelial and liver sinusoidal endothelial cells reveal its toxic features in vitro

Several fatty acids, in particular saturated fatty acids like palmitic acid, cause lipotoxicity in the context of non-alcoholic fatty liver disease . Unsaturated fatty acids (e.g. oleic acid) protect against lipotoxicity in hepatocytes. However, the effect of oleic acid on other liver cell types, in particular liver sinusoidal endothelial cells (LSECs), is unknown. Human umbilical vein endothelial cells (HUVECs) are often used as a substitute for LSECs, however, because of the unique phenotype of LSECs, HUVECs cannot represent the same biological features as LSECs. In this study, we investigate the effects of oleate and palmitate (the sodium salts of oleic acid and palmitic acid) on primary rat LSECs in comparison to their effects on HUVECs. Oleate induces necrotic cell death in LSECs, but not in HUVECs. Necrotic cell death of LSECs can be prevented by supplementation of 2-stearoylglycerol, which promotes cellular triglyceride (TG) synthesis. Repressing TG synthesis, by knocking down DGAT1 renders HUVECs sensitive to oleate-induced necrotic death. Mechanistically, oleate causes a sharp drop of intracellular ATP level and impairs mitochondrial respiration in LSECs. The combination of oleate and palmitate reverses the toxic effect of oleate in both LSECs and HUVECs. These results indicate that oleate is toxic and its toxicity can be attenuated by stimulating TG synthesis. The toxicity of oleate is characterized by mitochondrial dysfunction and necrotic cell death. Moreover, HUVECs are not suitable as a substitute model for LSECs.

Microscopic polyangiitis plasma-derived exosomal miR-1287-5p induces endothelial inflammatory injury and neutrophil adhesion by targeting CBL

Background

An inflammatory environment around the vessel wall caused by leukocyte infiltration is one of the characteristic histopathological features of microscopic polyangiitis (MPA); however, the pathogenic mechanisms are not fully understood. Studies have found that circulating microRNA (miRNA) can be used as potential biomarkers for the diagnosis and classification of anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitides (AAV), and the E3 ubiquitin ligase casitas B-lineage lymphoma (CBL) seems to be associated with inflammation. In addition, evidence indicates that miRNA can be tracked into exosomes and transferred into recipient cells to mediate the process of vascular endothelial injury. Herein, we aimed to identify the profiles of exosomal miRNA, and determine the effect of exosomal miR-1287-5p and its target gene CBL on vascular endothelial cells in MPA.

Method

We isolated plasma exosomes from patients with MPA (MPA-exo) and healthy controls (HC-exo) by ultracentrifugation and conducted exosome small-RNA sequencing to screen differential miRNA expression in MPA-exo (n = 3) compared to HC-exo (n = 3). We measured the expression levels of miR-1303, miR-1287-5p, and miR-129-1-3p using quantitative reverse transcription-polymerase chain reaction (qRT-PCR, n = 6) and performed dual luciferase reporter gene assays to confirm the downstream target gene of miR-1287-5p. In addition, we treated human umbilical vein endothelial cell (HUVEC) with MPA-exo, or transfected them with miR-1287-5p mimic/inhibitor or with CBL-siRNA/CBL-siRNA+ miR-1287-5p inhibitor. After cell culture, we evaluated the effects on vascular endothelial cells by examining the mRNA levels of IL-6, IL-8, MCP-1, ICAM-1 and E-selectin using qRT-PCR and performed neutrophil adhesion assay with haematoxylin staining.

Result

Transmission electron microscopy, Western blot and nanoparticle tracking analysis showed that we successfully purified exosomes and MPA-exo could be absorbed into HUVEC. We screened a total of 1,077 miRNA by sequencing and observed a high abundance of miR-1287-5p in the exosomes obtained from MPA plasma. The dual luciferase reporter assay identified CBL as a downstream target gene of miR-1287-5p, and the results revealed that MPA-exo decreased CBL protein expression in HUVEC. In addition, treatment with MPA-exo, up-regulating miR-1287-5p or silencing of CBL in HUVEC significantly increased the mRNA expression of inflammatory factors (including IL-6, IL-8, and MCP-1) and adhesion molecules (including ICAM-1 and E-selection) and promoted the adhesion of neutrophils to HUVEC. However, down-regulating miR-1287-5p had the opposite effect.

Conclusion

Our study revealed that MPA-exo was involved in the intercellular transfer of miR-1287-5p and subsequently promote the development of acute endothelial injury in MPA. MiR-1287-5p and CBL agonists may be promising therapeutic approach for MPA-induced vascular inflammatory injury.

Genetic background strongly influences the transition to chronic kidney disease of adriamycin nephropathy in mice

Animal models of podocytopathy and chronic kidney diseases (CKD) help elucidate these pathologies. Adriamycin (ADR)-induced nephropathy is a common rodent model of podocytopathy. BALB/c mice are sensitive to ADR, whereas C57BL/6 (B6) mice, the most commonly used strain, are resistant to ADR. Therefore, mouse strains with the B6 genetic background cannot be used as an ADR nephropathy model. We previously generated DNA-dependent protein kinase catalytic subunit (Prkdc) mutant B6 mice (B6-Prkdc^R2140C) carrying the R2140C mutation that causes ADR nephropathy. However, whether ADR nephropathy in the novel strain progresses to CKD after ADR administration has not been evaluated. Therefore, we examined whether the B6-Prkdc^R2140C mice develop CKD after ADR administration. We also evaluated whether differences existed in the genetic background in ADR nephropathy by comparing the B6-Prkdc^R2140C mice with BALB/c mice. Our findings demonstrated that B6-Prkdc^R2140C progresses to CKD and is resistant to nephropathy compared with the BALB/c mice. The B6-Prkdc^R2140C and BALB/c mice differed in the expression of genes related to inflammatory mediators, and further analysis is required to identify factors that contribute to resistance to nephropathy.

Salvia miltiorrhiza polysaccharides ameliorates Staphylococcus aureus-induced mastitis in rats by inhibiting activation of the NF-κB and MAPK signaling pathways

The lactation capacity of dairy cows is critical to the productivity of the animals. Mastitis is a disease that directly affects the lactation capacity of cows. Staphylococcus aureus (S. aureus) is one of the most important pathogens that causes mastitis in dairy cows. The anti-inflammatory effect of Salvia miltiorrhiza polysaccharides (SMPs) has been demonstrated in mice and chickens. However, the effectiveness of SMPs in preventing and treating mastitis is unclear. Therefore, the purpose of this study was to explore the protective effect and mechanism of SMPs on mastitis caused by S. aureus. S. aureus was used to induce mastitis in rats, and three doses of SMPs (87.5, 175, 350 mg/kg, BW/d) were administered as treatments. The bacterial load, histopathology, and myeloperoxidase (MPO) and N-acetyl-β-D-glucosaminidase (NAGase) activities of mammary glands were observed and measured. Cytokines, including interleukin (IL)-1β, interleukin (IL)-6, and tumor necrosis factor α (TNF-α), were examined by qRT-PCR and ELISA. Key proteins in the NF-κB and MAPK signaling pathways were analyzed by Western blotting. The results showed that SMP supplementation could significantly reduce the colonization of S. aureus and the recruitment of inflammatory cells in mammary glands. S. aureus-induced gene transcription and protein expression of IL-1β, IL-6, and TNF-α were significantly suppressed in mammary glands. In addition, the increase in NF-κB and MAPK protein phosphorylation was inhibited by SMPs. These results revealed that supplementation with SMPs protected the mammary gland of rats against damage caused by S. aureus and alleviated the inflammatory response. This study provides a certain experimental basis for the treatment of S. aureus-induced mastitis with SMPs in the future.

Clinical significance and role of CXCL16 in anti-neutrophil cytoplasmic autoantibody-associated vasculitis

Anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) is a group of potentially life-threatening autoimmune diseases. The kidney and lung are the most common and most severely affected organs. Previous studies have shown that the chemokine ligand CXCL16 and its receptor CXCR6 play an important role in kidney disease. However, whether CXCL16/CXCR6 is involved in the pathogenesis of AAV remains elusive. In this study, the levels of CXCL16 and its specific receptor CXCR6 were investigated. According to kidney outcome, patients were divided into two groups, specifically one with high CXCL16 levels and one with low CXCL16 levels, by cut-off values using receiver operating characteristic (ROC) curves. The clinical parameters and histological features were further compared between the two groups. The ability of CXCL16 to induce neutrophil chemotaxis was analysed using a Transwell migration assay in a coculture system of conditional immortalized human glomerular endothelial cells (ciGEnCs) and neutrophils. We observed that the levels of CXCL16 were significantly increased in the circulation, along with the expression in renal tissue of AAV patients compared to healthy controls (HCs). CXCR6 expression on neutrophils was significantly higher in patients with AAV than in HCs. There were positive correlations between the levels of CXCL16 and serum creatinine, IL-6, CRP, and TNF-α and negative correlations with eGFR. The serum levels of CXCL16 could act as a predictive biomarker of renal outcome in AAV. CXCL16 secretion was upregulated in ciGEnCs treated with AAV serum. CXCL16 released from ciGEnCs contributed to neutrophil migration. Furthermore, neutrophil migration was attenuated by silencing CXCL16 expression via transfection with short hairpin RNA (shRNA) sequences and lentivirus. Taken together, these data suggest that the inhibition of the CXCL16/CXCR6 axis may provide new therapeutic strategies targeting AAV.

The biomechanistic aspects of renal cortical injury induced by diesel exhaust particles in rats and the renoprotective contribution of quercetin pretreatment: Histological and biochemical study

Although several studies have reported a toxic effect of diesel exhaust particles (DEP) exposure on the kidney tissues, the involvement of autophagy/NF-kB signaling as encountered mechanisms and the protective effects of a natural flavonoid, quercetin on DEP remains unclear. Thirty-two albino rats were divided as control, quercetin-treated (60 mg/kg, oral), DEP-exposed (0.5 mg/kg, intra-tracheal), and quercetin/DEP-exposed groups. Specimens of the renal cortex were subjected to histo-biochemical study and immunohistochemical analysis using anti-NF-kB, and anti-LC3β antibodies followed by morphometric and statistical analyses. The expression level of autophagy genes was quantitatively evaluated using RT-PCR, as well. The DEP-exposed rats showed an elevation in the renal tissue levels of MDA and a decrease in the catalase and superoxide dismutase (p < .05). Histologically, there were cytoplasmic vacuolar changes in the lining cells of the renal tubules, glomerular atrophy, and vascular congestion. In addition, renal inflammation was evident as confirmed by the increased NF-kB immunoexpression. Moreover, the gene expression of Becn1, ATG5, and LC3β increased (p <. 0) due to DEP exposure. Conversely, quercetin pretreatment improved these renal histo-biochemical alterations (p < .05) and regulated autophagy/NF-kB pathways. Overall, the study proved the renal toxicity mediated by DEP exposure via precipitating renal inflammation, autophagy activation, and oxidative stress. Quercetin pretreatment could antagonize such machinery to protect the kidney against DEP.

Cardiovascular disease and ANCA-associated vasculitis: Are we missing a beat?

The association between cardiovascular (CV) disease and anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is well documented. The recent work by Massicotte-Azarniouch et al. confirms the risk and adds to the existing evidence by describing the highest risk in the first 3 months after diagnosis. In this review, we aim to put their findings into perspective and formulate implications for the care of AAV patients. We discuss mechanisms for increased CV disease in AAV, including the impact of traditional risk factors and disease-related risks such as renal impairment and anti-myeloperoxidase (MPO) ANCA serotype. We also provide a brief primer on the impact of inflammatory-driven endothelial dysfunction and platelet activation on accelerated atherosclerosis in AAV patients. These features alongside the impact of disease activity and systemic inflammation provide potential explanations to why the incidence of CV events is highest in the first 3 months from diagnosis. We suggest future avenues of research, provide some suggestions to address and treat CV risk based on current evidence, and highlight the importance of addressing this topic early on. Addressing modifiable risk factors, dialogue with patients, patient information and a structured approach overall will be key to improve CV outcomes in AAV.

Role of Endothelial Glucocorticoid Receptor in the Pathogenesis of Kidney Diseases

Glucocorticoids, as multifunctional hormones, are widely used in the treatment of various diseases including nephrological disorders. They are known to affect immunological cells, effectively treating many autoimmune and inflammatory processes. Furthermore, there is a growing body of evidence demonstrating the potent role of glucocorticoids in non-immune cells such as podocytes. Moreover, novel data show additional pathways and processes affected by glucocorticoids, such as the Wnt pathway or autophagy. The endothelium is currently considered as a key organ in the regulation of numerous kidney functions such as glomerular filtration, vascular tone and the regulation of inflammation and coagulation. In this review, we analyse the literature concerning the effects of endothelial glucocorticoid receptor signalling on kidney function in health and disease, with special focus on hypertension, diabetic kidney disease, glomerulopathies and chronic kidney disease. Recent studies demonstrate the potential role of endothelial GR in the prevention of fibrosis of kidney tissue and cell metabolism through Wnt pathways, which could have a protective effect against disease progression. Another important aspect covered in this review is blood pressure regulation though GR and eNOS. We also briefly cover potential therapies that might affect the endothelial glucocorticoid receptor and its possible clinical implications, with special interest in selective or local GR stimulation and potential mitigation of GC treatment side effects.

Diversity of NF-κB signalling and inflammatory heterogeneity in Rheumatic Autoimmune Disease

Systemic Autoimmune Rheumatic Diseases, including Rheumatoid Arthritis, Systemic Lupus Erythematosus and Sjogren's syndrome, are characterised by a loss of immune tolerance and chronic inflammation. There is marked heterogeneity in clinical and molecular phenotypes in each condition, and the aetiology of these is unclear. NF-κB is an inducible transcription factor that is critical in the physiological inflammatory response, and which has been implicated in chronic inflammation. Genome-wide association studies have linked risk alleles related to the NF-κB pathway to the pathogenesis of multiple Systemic Autoimmune Rheumatic Diseases. This review describes how cell- and pathway-specific NF-κB activation contribute to the spectrum of clinical phenotypes and molecular pathotypes in rheumatic disease. Potential clinical applications are explored, including therapeutic interventions and utilisation of NF-κB as a biomarker of disease subtypes and treatment response.

Serum Clusterin Level Could Reflect the Current Activity of Antineutrophil Cytoplasmic Antibody-Associated Vasculitis

PURPOSE

We investigated whether serum clusterin levels could reflect the current antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV)-specific indices.

MATERIALS AND METHODS

Fifty-seven patients with AAV and 40 healthy controls were included in this study. AAV-specific indices included the Short-Form 36-Item Health Survey Physical and Mental Component Summaries (SF-36 PCS and MCS) scores, Birmingham vasculitis activity score (BVAS), five-factor score (FFS), and vasculitis damage index. Clinical and laboratory data and AAV-specific indices were obtained at blood collection. The highest tertile of BVAS (≥16) was defined as high activity of AAV.

RESULTS

The median age of AAV patients was 64.0 years and 19 patients were male. SF-36 PCS score (r=0.328), SF-36 MCS score (r=0.289), BVAS (r=-0.404), erythrocyte sedimentation rate (r=-0.336), and C-reactive protein levels (r=-0.421) were significantly correlated with serum clusterin levels. In the multivariable linear regression analysis using AAV-specific indices and serum clusterin levels, both FFS (β=0.412) and serum clusterin levels (β=-0.250) were significantly associated with BVAS. When the optimal serum clusterin cut-off level for high activity of AAV was identified as 130.45 µg/mL, patients with serum clusterin level ≤130.45 µg/mL had a significantly higher risk for high activity of AAV than did those without (relative risk 7.194). Patients with AAV exhibited significantly lower serum clusterin levels than did healthy controls (168.2 µg/mL vs. 230.5 µg/mL).

CONCLUSION

Serum clusterin levels could reflect the current disease activity in patients with AAV.

Effect of silymarin on intestinal injury and PI3K/Akt and NF-κB signaling pathways in rats with severe acute pancreatitis

BACKGROUND

Acute pancreatitis is a very common clinical acute abdomen. Excessive release of inflammatory factors can damage the intestinal mucosa, induce cell apoptosis, and accelerate the course of the disease. Silymarin has anti-oxidative, immunoregulatory, anti-inflammatory, liver-protecting, anti-tissue fibrosis, and other effects. However, there is no relevant research on the effect of silymarin on the intestinal injury in severe acute pancreatitis.

AIM

To study the effects of silymarin on intestinal injury and PI3K/Akt and NF-κB signaling pathways in rats with severe acute pancreatitis.

METHODS

Rats were divided into a control group, a severe acute pancreatitis (SAP) model group, and low-, medium, and high-dose silymarin groups (severe acute pancreatitis rats given 60, 120 , and 240 mg/kg silymarin, respectively). Rats treated with glutamine (1.5 g/kg) were used as positive controls. The death of rats was recorded. Serum amylase and lipase levels were detected using an automatic biochemical analyzer. Serum IL-1β and TNF-α levels were detected by ELISA. Pancreatic and ileal pathology scores were scalculated. The expression of Bcl-2, Bax, PI3K, p-PI3K, Akt, p-Akt, NF-κBp65, and Bcl-2 in ileal tissues was detected by Western blot. TUNEL method was used to detect cell apoptosis in ileal tissues.

RESULTS

The SAP group, control group, and low-, medium, and high-dose silymarin groups had 3, 0, 2, 1, and 0 deaths, respectively. Compared with the control group, the levels of serum amylase, lipase, IL-1β, and TNF-α , the pancreatic and ileal pathology scores, the levels of Bax, p-PI3K/PI3K, p-Akt/Akt, and NF-κBp65, and the apoptosis index increased, while Bcl-2 protein expression decreased in the SAP group. Compared with the SAP group, the levels of serum amylase, lipase, IL-1β, and TNF-αased, the pancreatic and ileal pathology scores, the levels of Bax, p-PI3K/PI3K, p-Akt/Akt, and NF-κBp65 protein levels, and the apoptosis index gradually decreased, while Bcl-2 protein expression gradually increased in the low-, medium, and high-dose silymarin groups. Compared with the SAP group, the serum levels of amylase, lipase, IL-1β, and TNF-α, the pancreatic and ileal pathology scores, the levels of Bax, p-PI3K/PI3K, p-Akt/Akt, and NF-κBp65, and the apoptosis index decreased, while Bcl-2 protein expression increased in the glutamine group.

CONCLUSION

Silymarin can reduce intestinal injury in rats with SAP, inhibit inflammation, reduce cell apoptosis, and inhibit the activation of the PI3K/Akt and NF-κB signaling pathways.

MiR-494-mediated Effects on the NF-κB Signaling Pathway Regulate Lipopolysaccharide-Induced Acute Kidney Injury in Mice

OBJECTIVE

To explore the effects of miR-494 inhibition through the NF-κB signaling pathway on lipopolysaccharide (LPS)-induced acute kidney injury (AKI) mouse model.

METHODS

The AKI mice induced by LPS were treated with miR-494 antagomir, and the kidney parameters and indicators of oxidative stress were detected. HE and TUNEL staining were performed to observe the kidney histopathology and the apoptosis in renal tubular epithelial cells (RTECs), respectively. The ROS level was measured using dihydroethidium (DHE) staining. In addition, qRT-PCR, western blotting, immunohistochemistry (IHC), and ELISA were also used to detect gene or protein expression.

RESULTS

LPS-induced AKI mice injected with the miR-494 antagomir showed reduced blood urea nitrogen (BUN) and serum creatinine (Cr) with improved kidney histopathology. The expression levels of p-IKKα/β, p-IκBα and p65 NF-κB in the nucleus were increased in kidney tissues from the LPS-induced AKI mice, and they were decreased by the miR-494 antagomir. Moreover, the results of IHC showed that the miR-494 antagomir downregulated p65 NF-κB in kidney tissues from the LPS-induced AKI mice, accompanied by decreased levels of TNF-α, IL-1β, IL-6, MDA, NO, and ROS but increased levels of SOD and GSH. In addition, the LPS-induced AKI mice had increased apoptosis in RTECs, as well as increased Caspase-3 and Bax and decreased Bcl-2, which were reversed by the miR-494 antagomir.

CONCLUSIONS

The inhibition of miR-494 could reduce inflammatory responses and improve oxidative stress in kidney tissues from LPS-induced AKI mice by blocking the NF-κB pathway accompanying by reduced apoptosis in RTECs.

Retinoic acid receptor responder1 promotes development of glomerular diseases via the Nuclear Factor-κB signaling pathway

Inflammatory pathways are activated in most glomerular diseases but molecular mechanisms driving them in kidney tissue are poorly known. We identified retinoic acid receptor responder 1 (Rarres1) as a highly podocyte-enriched protein in healthy kidneys. Studies in podocyte-specific knockout animals indicated that Rarres1 was not needed for the normal development or maintenance of the glomerulus filtration barrier and did not modulate the outcome of kidney disease in a model of glomerulonephritis. Interestingly, we detected an induction of Rarres1 expression in glomerular and peritubular capillary endothelial cells in IgA and diabetic kidney disease, as well as in ANCA-associated vasculitis. Analysis of publicly available RNA data sets showed that the induction of Rarres1 expression was a common molecular mechanism in chronic kidney diseases. A conditional knock-in mouse line, overexpressing Rarres1 specifically in endothelial cells, did not show any obvious kidney phenotype. However, the overexpression promoted the progression of kidney damage in a model of glomerulonephritis. In line with this, conditional knock-out mice, lacking Rarres1 in endothelial cells, were partially protected in the disease model. Mechanistically, Rarres1 promoted inflammation and fibrosis via transcription factor Nuclear Factor-κB signaling pathway by activating receptor tyrosine kinase Axl. Thus, induction of Rarres1 expression in endothelial cells is a prevalent molecular mechanism in human glomerulopathies and this seems to have a pathogenic role in driving inflammation and fibrosis via the Nuclear Factor-κB signaling pathway.

Granulomatous Inflammation in ANCA-Associated Vasculitis

ANCA-associated vasculitis (AAV) comprises granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). While systemic vasculitis is a hallmark of all AAV, GPA is characterized by extravascular granulomatous inflammation, preferentially affecting the respiratory tract. The mechanisms underlying the emergence of neutrophilic microabscesses; the appearance of multinucleated giant cells; and subsequent granuloma formation, finally leading to scarred or destroyed tissue in GPA, are still incompletely understood. This review summarizes findings describing the presence and function of molecules and cells contributing to granulomatous inflammation in the respiratory tract and to renal inflammation observed in GPA. In addition, factors affecting or promoting the development of granulomatous inflammation such as microbial infections, the nasal microbiome, and the release of damage-associated molecular patterns (DAMP) are discussed. Further, on the basis of numerous results, we argue that, in situ, various ways of exposure linked with a high number of infiltrating proteinase 3 (PR3)- and myeloperoxidase (MPO)-expressing leukocytes lower the threshold for the presentation of an altered PR3 and possibly also of MPO, provoking the local development of ANCA autoimmune responses, aided by the formation of ectopic lymphoid structures. Although extravascular granulomatous inflammation is unique to GPA, similar molecular and cellular patterns can be found in both the respiratory tract and kidney tissue of GPA and MPA patients; for example, the antimicrobial peptide LL37, CD163⁺ macrophages, or regulatory T cells. Therefore, we postulate that granulomatous inflammation in GPA or PR3-AAV is intertwined with autoimmune and destructive mechanisms also seen at other sites.

MicroRNA-340-5p inhibits endothelial apoptosis, inflammatory response, and pro-coagulation by targeting KDM4C in anti-neutrophil cytoplasmic antibody (ANCA)-mediated glomerulonephritis through activation of B cells

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, a class of systemic autoimmune diseases, results in damage of various critical organs including kidneys, lungs, eyes, and nervous system. MicroRNA-340-5p was confirmed to be downregulated in autoimmune pathogenesis. However, the role of miR-340-5p remains unknown in ANCA-induced glomerulonephritis (GN). The current study aimed to explore the role of miR-340-5p in ANCA-induced GN. The animal models of ANCA-induced GN was established by experimental autoimmune vasculitis (EAV) operation. The primary glomerular endothelial cells (PGEnCs) were treated with anti-myeloperoxidase (anti-MPO) to mimic cell injury in vitro. The renal function was analysed by measuring serum creatinine, blood urea nitrogen, urine blood, urine protein and urine leukocytes. The levels of RNA and proteins were examined by RT-qPCR and western blot analysis, respectively. The binding capacity between miR-340-5p and KDM4C was detected by luciferase reporter assay. Cell apoptosis was analysed by flow cytometry in vitro. Cell viability was determined by CCK-8 assay. The cleaved caspase-3 activity was analysed by immunofluorescent assay. Cell inflammation was measured by western blot. Cell procoagulant activity was assessed by FXa generation assay. The histological changes of renal tissues were assessed by Haematoxylin and eosin (H&E) staining assay. The correlation between miR-340-5p and KDM4C level (or content of TNF-α and IL-6) was analysed by Pearson correlation analysis. The injection of anti-MPO IgG induced a significant elevation of Serum creatinine and blood urea nitrogen in serum, as well as urine blood, urine protein and urine leukocytes. Importantly, KDM4C was downregulated in model group. In mechanism, we identified that miR-340-5p bound with KDM4C 3'untranslated region (UTR), negatively regulated KDM4C in endothelial cells and negatively correlated with KDM4C in serum of GN rats. In function, we found that miR-340-5p promoted B cell activation and proliferation by downregulating KDM4C. The in vitro assays showed that the decrease of cell viability induced by anti-MPO was reversed by miR-340-5p overexpression, and further reduced by KDM4C overexpression. Inversely, the suppressive effects of miR-340-5p mimics on cell apoptosis, cleaved caspase-3 activity, inflammatory response and pro-coagulation were countervailed by KDM4C overexpression in anti-MPO-treated cells. The in vivo assays validated that miR-340-5p overexpression mitigated the impairment of renal function, and histological changes induced by anti-MPO IgG injection in model group. Finally, we found the negative correlation between miR-340-5p and TNF-α (or IL-6) content in serum of GN rats. In conclusion, we found that miR-340-5p inhibited endothelial apoptosis and inflammatory response by targeting KDM4C in ANCA-mediated GN through activation of B cells, implying a potential novel insight for treatment of ANCA-mediated GN.

Unraveling the epigenetic landscape of glomerular cells in kidney disease

Chronic kidney disease (CKD) is a major public health concern and its prevalence and incidence are rising quickly. It is a non-communicable disease primarily caused by diabetes and/or hypertension and is associated with high morbidity and mortality. Despite decades of research efforts, the pathogenesis of CKD remains a puzzle with missing pieces. Understanding the cellular and molecular mechanisms that govern the loss of kidney function is crucial. Abrupt regulation of gene expression in kidney cells is apparent in CKD and shown to be responsible for disease onset and progression. Gene expression regulation extends beyond DNA sequence and involves epigenetic mechanisms including changes in DNA methylation and post-translational modifications of histones, driven by the activity of specific enzymes. Recent advances demonstrate the essential participation of epigenetics in kidney (patho)physiology, as its actions regulate both the integrity of cells but also triggers deleterious signaling pathways. Here, we review the known epigenetic processes regulating the complex filtration unit of the kidney, the glomeruli. The review will elaborate on novel insights into how epigenetics contributes to cell injury in the CKD setting majorly focusing on kidney glomerular cells: the glomerular endothelial cells, the mesangial cells, and the specialized and terminally differentiated podocyte cells.

Pathogenesis of ANCA-associated vasculitis: an emerging role for immunometabolism

ANCA-associated vasculitis (AAV) is a severe systemic autoimmune disease. A key feature of AAV is the presence of Anti-Neutrophil Cytoplasmic Antibodies (ANCA) directed against myeloperoxidase (MPO) or proteinase-3 (PR3). ANCA are key to the pathogenesis of AAV, where they activate innate immune cells to drive inflammation. Pre-activation or 'priming' of immune cells appears to be important for complete cellular activation in AAV. The burgeoning field of immunometabolism has illuminated the governance of immune cell function by distinct metabolic pathways. There is ample evidence that the priming events synonymous with AAV alter immune cell metabolism. In this review we discuss the pathogenesis of AAV and its intersection with recent insights into immune cell metabolism.

Glomerular Endothelial Cells as Instigators of Glomerular Sclerotic Diseases

Glomerular endothelial cell (GEnC) dysfunction is important in the pathogenesis of glomerular sclerotic diseases, including Focal Segmental Glomerulosclerosis (FSGS) and overt diabetic nephropathy (DN). GEnCs form the first cellular barrier in direct contact with cells and factors circulating in the blood. Disturbances in these circulating factors can induce GEnC dysfunction. GEnC dysfunction occurs in early stages of FSGS and DN, and is characterized by a compromised endothelial glycocalyx, an inflammatory phenotype, mitochondrial damage and oxidative stress, aberrant cell signaling, and endothelial-to-mesenchymal transition (EndMT). GEnCs are in an interdependent relationship with podocytes and mesangial cells, which involves bidirectional cross-talk via intercellular signaling. Given that GEnC behavior directly influences podocyte function, it is conceivable that GEnC dysfunction may culminate in podocyte damage, proteinuria, subsequent mesangial activation, and ultimately glomerulosclerosis. Indeed, GEnC dysfunction is sufficient to cause podocyte injury, proteinuria and activation of mesangial cells. Aberrant gene expression patterns largely contribute to GEnC dysfunction and epigenetic changes seem to be involved in causing aberrant transcription. This review summarizes literature that uncovers the importance of cross-talk between GEnCs and podocytes, and GEnCs and mesangial cells in the context of the development of FSGS and DN, and the potential use of GEnCs as efficacious cellular target to pharmacologically halt development and progression of DN and FSGS.

The TLR4-MyD88-NF-κB pathway is involved in sIgA-mediated IgA nephropathy

Previous studies have shown that secretory IgA (sIgA) was critically involved in IgA nephropathy (IgAN) immune responses. Toll-like receptors (TLRs), especially TLR4 which participates in mucosal immunity, may be involved in the pathogenesis of IgAN. The purpose of this study was to investigate whether sIgA and TLR4 interact to mediate kidney damage in IgAN patients. IgAN patients with positive sIgA deposition in renal tissues were screened by immunofluorescence assay. Patient salivary sIgA (P-sIgA) was collected and purified by jacalin affinity chromatography. Salivary sIgA from healthy volunteers was used as a control (N-sIgA). Expression of TLR4, MyD88, NF-κB, TNF-α, IL-6, and MCP-1 were detected in the mesangial area of IgAN patients by immunohistochemistry, the expression levels in patients with positive sIgA deposition were higher than that with negative sIgA deposition. Human renal mesangial cells (HRMCs) were cultured in vitro, flow cytometry showed that P-sIgA bound HRMCs significantly better than N-sIgA. HRMCs were cultured in the presence of sIgA (400 μg/mL) for 24 h, compared with cells cultured with N-sIgA, HRMCs cultured in vitro with P-sIgA showed enhanced expression of TLR4, increased secretion of TNF-α, IL-6, and MCP-1, and increased expression of MyD88/NF-κB. TLR4 shRNA silencing and NF-κB inhibition both reduced the ability of HRMCs to synthesize TNF-α, IL-6, and MCP-1. Our results indicate that sIgA may induce high expression of TLR4 in HRMCs and further activate downstream signalling pathways, prompting HRMCs to secrete multiple cytokines and thereby mediating kidney damage in IgAN patients.

Animal Models of ANCA Associated Vasculitis

Anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV) is a rare and severe autoimmune multisystemic disease. Its pathogenesis involves multiple arms of the immune system, as well as complex interactions between immune cells and target organs. Experimental animal models of disease can provide the crucial link from human disease to translational research into new therapies. This is particularly true in AAV, due to low disease incidence and substantial disease heterogeneity. Animal models allow for controlled environments in which disease mechanisms can be defined, without the clinical confounders of environmental and lifestyle factors. To date, multiple animal models have been developed, each of which shed light on different disease pathways. Results from animal studies of AAV have played a crucial role in enhancing our understanding of disease mechanisms, and have provided direction toward newer targeted therapies. This review will summarize our understanding of AAV pathogenesis as has been gleaned from currently available animal models, as well as address their strengths and limitations. We will also discuss the potential for current and new animal models to further our understanding of this important condition.

Endothelium structure and function in kidney health and disease

The kidney harbours different types of endothelia, each with specific structural and functional characteristics. The glomerular endothelium, which is highly fenestrated and covered by a rich glycocalyx, participates in the sieving properties of the glomerular filtration barrier and in the maintenance of podocyte structure. The microvascular endothelium in peritubular capillaries, which is also fenestrated, transports reabsorbed components and participates in epithelial cell function. The endothelium of large and small vessels supports the renal vasculature. These renal endothelia are protected by regulators of thrombosis, inflammation and complement, but endothelial injury (for example, induced by toxins, antibodies, immune cells or inflammatory cytokines) or defects in factors that provide endothelial protection (for example, regulators of complement or angiogenesis) can lead to acute or chronic renal injury. Moreover, renal endothelial cells can transition towards a mesenchymal phenotype, favouring renal fibrosis and the development of chronic kidney disease. Thus, the renal endothelium is both a target and a driver of kidney and systemic cardiovascular complications. Emerging therapeutic strategies that target the renal endothelium may lead to improved outcomes for both rare and common renal diseases.

NFκB and Kidney Injury

The global burden of chronic kidney disease will increase during the next century. As NFκB, first described more than 30 years ago, plays a major role in immune and non-immune-mediated diseases and in inflammatory and metabolic disorders, this review article summarizes current knowledge on the role of NFκB in in vivo kidney injury and describes the new and so far not completely understood crosstalk between canonical and non-canonical NFκB pathways in T-lymphocyte activation in renal disease.

ATG5-mediated autophagy suppresses NF-κB signaling to limit epithelial inflammatory response to kidney injury

G2/M-arrested proximal tubular epithelial cells (TECs) after renal injury are linked to increased cytokines production. ATG5-mediated autophagy in proximal TECs has recently been shown to protect against G2/M cell cycle arrest and renal fibrosis. However, the impacts of autophagy in regulating inflammatorily response mounted by injured TECs remains largely unknown. In the present study, we investigated whether ATG5 acts as an innate immune suppressor in proximal TECs during kidney injury. Using the unilateral ureteric obstruction model in proximal tubule-specific autophagy-deficient mice, we demonstrated that ablation of epithelial ATG5 genes markedly impaired autophagy, resulting in enhanced nuclear factor κB (NF-κB) activation, macrophage and lymphocyte infiltration, and proinflammatory cytokines production in obstructed kidneys, as compared with wild-type mice. Following stimulation with angiotensin II (Ang II), siRNA silencing of ATG5 in cultured HK-2 cells or ATG5-deficient primary proximal TECs produced more cytokines, including IL-1β, IL-6, and TNF-α than did their control cells. Overexpressed ATG5, but not the autophagy-incompetent ATG5 mutant K130R in HK-2 cells, rendered resistant to Ang II-induced inflammatory response. Immunofluorescence assay indicated that ATG5 and p65 colocalized in the nucleus and cytoplasm, and their interaction was verified in immunoprecipitation assay from HEK-293T cell extracts. Genetic downregulation of endogenous ATG5 increased Ang II-induced phosphorylation and nuclear translocation of p65 and transcriptional activity of NF-κB, whereas the overexpressed ATG5, rather than ATG5 mutant K130R, hampered activation of NF-κB signaling, suggest an autophagy-dependent anti-inflammatory effect of ATG5. Further, pharmacological manipulation of autophagy yielded similar results both in vivo and in vitro. Additionally, JSH-23, a specific inhibitor of NF-κB nuclear translocation, rescued Ang II-driven IL-1β production in ATG5 siRNA-treated cells and decreased the proportion of cells in G2/M phase. In conclusion, ATG5-mediated autophagy in tubules targets NF-κB signaling to protect against renal inflammation.

Endothelium structure and function in kidney health and disease

The kidney harbours different types of endothelia, each with specific structural and functional characteristics. The glomerular endothelium, which is highly fenestrated and covered by a rich glycocalyx, participates in the sieving properties of the glomerular filtration barrier and in the maintenance of podocyte structure. The microvascular endothelium in peritubular capillaries, which is also fenestrated, transports reabsorbed components and participates in epithelial cell function. The endothelium of large and small vessels supports the renal vasculature. These renal endothelia are protected by regulators of thrombosis, inflammation and complement, but endothelial injury (for example, induced by toxins, antibodies, immune cells or inflammatory cytokines) or defects in factors that provide endothelial protection (for example, regulators of complement or angiogenesis) can lead to acute or chronic renal injury. Moreover, renal endothelial cells can transition towards a mesenchymal phenotype, favouring renal fibrosis and the development of chronic kidney disease. Thus, the renal endothelium is both a target and a driver of kidney and systemic cardiovascular complications. Emerging therapeutic strategies that target the renal endothelium may lead to improved outcomes for both rare and common renal diseases.

Targeted Transfection Using PEGylated Cationic Liposomes Directed Towards P-Selectin Increases siRNA Delivery into Activated Endothelial Cells

: The progress in small-interfering RNA (siRNA) therapeutics depends on the development of suitable nanocarriers to perform specific and effective delivery to dysfunctional cells. In this paper, we questioned whether P-selectin, a cell adhesion molecule specifically expressed on the surface of activated endothelial cells (EC) could be employed as a target for nanotherapeutic intervention. To this purpose, we developed and characterized P-selectin targeted PEGylated cationic liposomes able to efficiently pack siRNA and to function as efficient vectors for siRNA delivery to tumour necrosis factor-α (TNF-α) activated EC. Targeted cationic liposomes were obtained by coupling a peptide with high affinity for P-selectin to a functionalized PEGylated phospholipid inserted in the liposomes' bilayer (Psel-lipo). As control, scrambled peptide coupled cationic liposomes (Scr-lipo) were used. The lipoplexes obtained by complexation of Psel-lipo with siRNA (Psel-lipo/siRNA) were taken up specifically and at a higher extent by TNF-α activated b.End3 endothelial cells as compared to non-targeted Scr-lipo/siRNA. The Psel-lipo/siRNA delivered with high efficiency siRNA into the cells. The lipoplexes were functional as demonstrated by the down-regulation of the selected gene (GAPDH). The results demonstrate an effective targeted delivery of siRNA into cultured activated endothelial cells using P-selectin directed PEGylated cationic liposomes, which subsequently knock-down the desired gene.

Endothelium-targeted delivery of dexamethasone by anti-VCAM-1 SAINT-O-Somes in mouse endotoxemia

Microvascular endothelial cells play a pivotal role in the pathogenesis of sepsis-induced inflammatory responses and multiple organ failure. Therefore, they represent an important target for pharmacological intervention in the treatment of sepsis. Glucocorticosteroids were widely used in the treatment of sepsis but vast evidence to support their systemic use is lacking. The limited effects of glucocorticoids in the treatment of sepsis may be explained by differential effects of drug initiated NF-κB inhibition in different cell types and insufficient drug delivery in target cells. The current study aimed therefore to investigate the effects of an endothelial targeted delivery of dexamethasone in a mouse model of endotoxemia induced by two consecutive i.p. injections of lipopolysaccharide (LPS). To achieve endothelial cell specific delivery of dexamethasone, we modified SAINT-O-Somes, a new generation of liposomes that contain the cationic amphiphile SAINT-C18 (1-methyl-4-(cis-9-dioleyl) methyl-pyridinium chloride, with antibodies against vascular cell adhesion molecule-1 (VCAM-1). In LPS challenged mice, the systemic administration of free dexamethasone had negligible effects on the microvascular inflammatory endothelial responses. Dexamethasone-loaded anti-VCAM-1 SAINT-O-Somes specifically localized at VCAM-1 expressing endothelial cells in the microvasculature of inflamed organs. This was associated with a marginal attenuation of the expression of a few pro-inflammatory genes in kidney and liver, while no effects in the lung were observed. This study reveals that, although local accumulation of the targeted drug was achieved, endothelial targeted dexamethasone containing anti-VCAM-1 SAINT-O-Somes exhibited marginal effects on inflammatory endothelial cell activation in a model of endotoxemia. Studies with more potent drugs encapsulated into anti-VCAM-1 SAINT-O-Somes will in the future reveal whether this delivery system can be further developed for efficacious endothelial directed delivery of drugs in the treatment of sepsis.