Hypermethylation leads to the loss of HOXA5, resulting in JAG1 expression and NOTCH signaling contributing to kidney fibrosis.

Epigenetic regulations, including DNA methylation, are critical to the development and progression of kidney fibrosis, but the underlying mechanisms remain elusive. Here, we show that fibrosis of the mouse kidney was associated with the induction of DNA methyltransferases and increases in global DNA methylation and was alleviated by the DNA methyltransferase inhibitor 5-Aza-2'-deoxycytidine (5-Aza). Genome-wide analysis demonstrated the hypermethylation of 94 genes in mouse unilateral ureteral obstruction kidneys, which was markedly reduced by 5-Aza. Among these genes, Hoxa5 was hypermethylated at its gene promoter, and this hypermethylation was associated with reduced HOXA5 expression in fibrotic mouse kidneys after ureteral obstruction or unilateral ischemia-reperfusion injury. 5-Aza prevented Hoxa5 hypermethylation, restored HOXA5 expression, and suppressed kidney fibrosis. Downregulation of HOXA5 was verified in human kidney biopsies from patients with chronic kidney disease and correlated with the increased kidney fibrosis and DNA methylation. Kidney fibrosis was aggravated by conditional knockout of Hoxa5 and alleviated by conditional knockin of Hoxa5 in kidney proximal tubules of mice. Mechanistically, we found that HOXA5 repressed Jag1 transcription by directly binding to its gene promoter, resulting in the suppression of JAG1-NOTCH signaling during kidney fibrosis. Thus, our results indicate that loss of HOXA5 via DNA methylation contributes to fibrogenesis in kidney diseases by inducing JAG1 and consequent activation of the NOTCH signaling pathway.

Hypermethylation suppresses microRNA-219a-2 to activate the ALDH1L2/GSH/PAI-1 pathway for fibronectin degradation in renal fibrosis.

Epigenetic regulations, such as DNA methylation and microRNAs, play an important role in renal fibrosis. Here, we report the regulation of microRNA-219a-2 (mir-219a-2) by DNA methylation in fibrotic kidneys, unveiling the crosstalk between these epigenetic mechanisms. Through genome-wide DNA methylation analysis and pyro-sequencing, we detected the hypermethylation of mir-219a-2 in renal fibrosis induced by unilateral ureter obstruction (UUO) or renal ischemia/reperfusion, which was accompanied by a significant decrease in mir-219a-5p expression. Functionally, overexpression of mir-219a-2 enhanced fibronectin induction during hypoxia or TGF-ß1 treatment of cultured renal cells. In mice, inhibition of mir-219a-5p suppressed fibronectin accumulation in UUO kidneys. ALDH1L2 was identified to be the direct target gene of mir-219a-5p in renal fibrosis. Mir-219a-5p suppressed ALDH1L2 expression in cultured renal cells, while inhibition of mir-219a-5p prevented the decrease of ALDH1L2 in UUO kidneys. Knockdown of ALDH1L2 enhanced PAI-1 induction during TGF-ß1 treatment of renal cells, which was associated with fibronectin expression. In conclusion, the hypermethylation of mir-219a-2 in response to fibrotic stress attenuates mir-219a-5p expression and induces the up-regulation of its target gene ALDH1L2, which may reduce fibronectin deposition by suppressing PAI-1.

TLR7-MyD88-DC-CXCL16 axis results neutrophil activation to elicit inflammatory response in pustular psoriasis.

Pustular psoriasis (PP) is a chronic inflammatory disease associated with multiple complications, often with hyperthermia and hypoproteinemia, and its continued progression can be life-threatening. Toll-like receptor 7 (TLR7) induces dendritic cell (DC) production of inflammatory factors that exacerbate the inflammatory response in PP. A membrane-bound chemokine expressed on DCs, CXC motif chemokine ligand 16 (CXCL16) is overexpressed in PP lesions, and neutrophils express its receptor CXC chemokine receptor 6 (CXCR6). There are few studies on the PP immune microenvironment and it is unclear whether TLR7 and CXCL16 can be used as targets in PP therapy. Skin tissue (n = 5) and blood (n = 20) samples were collected from PP and healthy normal controls. The skin tissue transcriptome was analyzed to obtain the differentially expressed genes, and the immune microenvironment was deciphered using pathway enrichment. Tissue sequencing analysis indicated that TLR7, CXCL16, DCs, and neutrophils were involved in the PP process. The enzyme-linked immunosorbent assay, reverse transcription-PCR, and scoring table results demonstrated that TLR7 induced DC secretion of CXCL16, which enabled neutrophil activation of the secretion of the inflammatory factors interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-α). The co-culture of neutrophils with DCs treated with TLR7 inhibitor or TLR7 agonist demonstrated that TLR7 regulated neutrophil activation, migration, and apoptosis. We constructed imiquimod-induced psoriasis-like skin lesions in wild-type, Cd11c-Cre Myd88f/f, and Mrp8-Cre Cxcr6f/f mice. The mouse models suggested that TLR7 might influence DC release of CXCL16 and neutrophil proinflammatory effects by interfering with the myeloid differentiation primary response gene 88 (MyD88) signaling pathway. In conclusion, the TLR7-MyD88-DC-CXCL16 axis is an important mechanism that promotes neutrophil migration to PP skin lesions and stimulates the inflammatory response.

RNA modifications: importance in immune cell biology and related diseases.

RNA modifications have become hot topics recently. By influencing RNA processes, including generation, transportation, function, and metabolization, they act as critical regulators of cell biology. The immune cell abnormality in human diseases is also a research focus and progressing rapidly these years. Studies have demonstrated that RNA modifications participate in the multiple biological processes of immune cells, including development, differentiation, activation, migration, and polarization, thereby modulating the immune responses and are involved in some immune related diseases. In this review, we present existing knowledge of the biological functions and underlying mechanisms of RNA modifications, including N6-methyladenosine (m6A), 5-methylcytosine (m5C), N1-methyladenosine (m1A), N7-methylguanosine (m7G), N4-acetylcytosine (ac4C), pseudouridine (Ψ), uridylation, and adenosine-to-inosine (A-to-I) RNA editing, and summarize their critical roles in immune cell biology. Via regulating the biological processes of immune cells, RNA modifications can participate in the pathogenesis of immune related diseases, such as cancers, infection, inflammatory and autoimmune diseases. We further highlight the challenges and future directions based on the existing knowledge. All in all, this review will provide helpful knowledge as well as novel ideas for the researchers in this area.

Abnormal lipid metabolism in epidermal Langerhans cells mediates psoriasis-like dermatitis.

Psoriasis is a chronic, inflammatory skin disease, frequently associated with dyslipidemia. Lipid disturbance in psoriasis affects both circulatory system and cutaneous tissue. Epidermal Langerhans cells (LCs) are tissue-resident DCs that maintain skin immune surveillance and mediate various cutaneous disorders, including psoriasis. However, the role of LCs in psoriasis development and their lipid metabolic alternation remains unclear. Here, we demonstrate that epidermal LCs of psoriasis patients enlarge with longer dendrites and possess elevated IL-23p19 mRNA and a higher level of neutral lipids when compared with normal LCs of healthy individuals. Accordantly, epidermal LCs from imiquimod-induced psoriasis-like dermatitis in mice display overmaturation, enhanced phagocytosis, and excessive secretion of IL-23. Remarkably, these altered immune properties in lesional LCs are tightly correlated with elevated neutral lipid levels. Moreover, the increased lipid content of psoriatic LCs might result from impaired autophagy of lipids. Bulk RNA-Seq analysis identifies dysregulated genes involved in lipid metabolism, autophagy, and immunofunctions in murine LCs. Overall, our data suggest that dysregulated lipid metabolism influences LC immunofunction, which contributes to the development of psoriasis, and therapeutic manipulation of this metabolic process might provide an effective measurement for psoriasis.

P2RY6 Has a Critical Role in Mouse Skin Carcinogenesis by Regulating the YAP and ß-Catenin Signaling Pathways.

P2RY6 is highly expressed in skin keratinocytes, but its function in skin diseases is unclear. We use a two-step chemical induction method to induce mouse skin tumor formation. Multiple in vitro and in vivo assays were used to explore the role of P2RY6 in skin tumors. We report that P2ry6-deficient mice exhibit marked resistance to 7,12-dimethylbenz[a]anthracene/12-O-tetradecanoylphorbol-13-acetate (TPA)-induced skin papilloma formation compared with wild-type mice. Consistent with these findings, epidermal hyperplasia in response to TPA was suppressed in the P2ry6-knockout or MRS2578 (P2RY6 antagonist)-treated mice. The dramatic decrease in hyperplasia and tumorigenesis due to P2ry6 disruption was associated with the suppression of TPA-induced keratinocyte proliferation and inflammatory reactions. Notably, P2ry6 deletion prevented the TPA-induced increase in YAP nuclear accumulation and its downstream gene expression in an MST/LATS1-dependent manner. On TPA stimulation, enhanced activation of MAPK/extracellular signal‒regulated kinase kinase 1 and ß-catenin were also impaired in P2ry6-knockout primary keratinocytes, tumor tissues, or MRS2578-treated HaCaT cells. Moreover, mutual promotion of the YAP and ß-catenin signaling pathways was observed in normal skin cells treated with TPA, whereas P2ry6 deletion could inhibit their crosstalk by regulating MAPK/extracellular signal‒regulated kinase kinase 1. Thus, P2RY6 is a critical positive regulator of skin tumorigenesis through the modulation of the Hippo/YAP and Wnt/ß-catenin signaling pathways.

IL-17A Promotes Psoriasis-Associated Keratinocyte Proliferation through ACT1-Dependent Activation of YAP-AREG Axis.

Psoriasis is a recurrent inflammatory skin disorder characterized by epidermal hyperplasia, which is primarily driven by IL-17A. The Hippo-YAP signaling pathway plays a vital role in cell survival and tissue growth, and its target gene, AREG, has been reported to promote the development of psoriasis. However, whether IL-17A promotes keratinocyte proliferation through regulating Hippo-YAP signaling has not been explored. In this study, we show that the YAP-AREG pathway is activated in human psoriatic skin and is suppressed by IL-17A antagonist secukinumab and that imiquimod and IL-17A administration activates the YAP-AREG axis in mice epidermis. In vitro studies using HaCaT and normal human epidermal keratinocyte cells suggest that IL-17A enhances AREG expression and keratinocyte proliferation by activating Hippo-YAP signaling. Mechanistically, IL-17A stimulates the recruitment of MST1 to ACT1 in keratinocytes, which leads to reduced MST1-LATS1 interaction and YAP dephosphorylation. Together, our findings reveal a previously unknown mechanism in which IL-17A promotes keratinocyte proliferation in psoriasis, namely through activating YAP-AREG signaling.

Human umbilical cord-derived mesenchymal stem cells ameliorate psoriasis-like dermatitis by suppressing IL-17-producing γδ T cells.

Mesenchymal stem cells (MSCs) have shown great potential in treating autoimmune diseases due to their immunomodulatory capability, which has been verified in both animal experiments and clinical trials. Psoriasis is a chronic and remitting immune-related disease. Limited studies have demonstrated that MSCs might be an effective therapeutic approach for managing psoriasis, whose underlying mechanism remains to be elucidated. In our present study, human umbilical cord-derived MSCs (hUC-MSCs) were subcutaneously injected into mice with imiquimod (IMQ)-induced psoriasis-like skin inflammation to explore the feasibility of this cellular therapy. The severity of psoriasis-like dermatitis was evaluated by cumulative psoriasis area and severity index score and epidermal thickness of skin tissue sections. Flow cytometric analysis was utilized to detect T helper cells, regulatory T cells, and γδ T cells in skin-draining lymph nodes. Real-time quantitative polymerase chain reaction and enzyme-linked immunosorbent assay were used to assess the expression levels of psoriasis-related cytokines and chemokines in mouse dorsal skin lesions. We discovered that hUC-MSCs drastically diminished the severity of IMQ-induced psoriasis-like dermatitis and suppressed inflammatory cell response. Although the tail vein injection of hUC-MSCs was also effective, it was correlated with higher mortality owing to pulmonary embolism. By comparison, subcutaneous injection with two million hUC-MSCs was identified to be the optimal therapeutic strategy. Furthermore, we uncovered that hUC-MSCs might repress skin inflammation probably through inhibiting interleukin-17-producing γδ T cells. In conclusion, subcutaneous administration of hUC-MSCs might be a promising therapeutic approach for psoriasis. Our findings provide novel insights into the underpinning mechanism of hUC-MSC treatment in the management of psoriasis.

Advances in the pathogenesis of psoriasis: from keratinocyte perspective.

Psoriasis is a complex long-lasting inflammatory skin disease with high prevalence and associated comorbidity. It is characterized by epidermal hyperplasia and dermal infiltration of immune cells. Here, we review the role of keratinocytes in the pathogenesis of psoriasis, focusing on factors relevant to genetics, cytokines and receptors, metabolism, cell signaling, transcription factors, non-coding RNAs, antimicrobial peptides, and proteins with other different functions. The critical role of keratinocytes in initiating and maintaining the inflammatory state suggests the great significance of targeting keratinocytes for the treatment of psoriasis.

Crosstalk between N6-methyladenosine modification and circular RNAs: current understanding and future directions.

N6-methyladenosine (m6A) is a prevalent internal modification in eukaryotic RNAs regulated by the so-called "writers", "erasers", and "readers". m6A has been demonstrated to exert critical molecular functions in modulating RNA maturation, localization, translation and metabolism, thus playing an essential role in cellular, developmental, and disease processes. Circular RNAs (circRNAs) are a class of non-coding RNAs with covalently closed single-stranded structures generated by back-splicing. CircRNAs also participate in physiological and pathological processes through unique mechanisms. Despite their discovery several years ago, m6A and circRNAs has drawn increased research interest due to advances in molecular biology techniques these years. Recently, several scholars have investigated the crosstalk between m6A and circRNAs. In this review, we provide an overview of the current knowledge of m6A and circRNAs, as well as summarize the crosstalk between these molecules based on existing research. In addition, we present some suggestions for future research perspectives.

Xiao-Yin-Fang Therapy Alleviates Psoriasis-like Skin Inflammation Through Suppressing γδT17 Cell Polarization.

Psoriasis is an immune-mediated chronic inflammatory skin disease primarily mediated by the activation of interleukin (IL)-17-producing T cells. Traditional Chinese Medicine (TCM) represents one of the most effective complementary and alternative medicine (CAM) agents for psoriasis, which provides treasured sources for the development of anti-psoriasis medications. Xiao-Yin-Fang (XYF) is an empirically developed TCM formula that has been used to treat psoriasis patients in Shanghai Changhai Hospital for over three decades. Imiquimod (IMQ)-induced psoriasis-like dermatitis mouse model was utilized to investigate the therapeutic effects of XYF by the assessment of disease severity and skin thickness. Flow cytometric assay was performed to explore the influence of XYF on skin-related immunocytes, primarily T cells. And, RNA sequencing analysis was employed to determine the alternation in gene expression upon XYF therapy. We discovered that XYF alleviated psoriasis-like skin inflammation mainly through suppressing dermal and draining lymph-node IL-17-producing γδT (γδT17) cell polarization. Moreover, XYF therapy ameliorated the relapse of psoriasis-like dermatitis and prohibited dermal γδT cell reactivation. Transcriptional analysis suggested that XYF might regulate various inflammatory signaling pathways and metabolic processes. In conclusion, our results clarified the therapeutic efficacy and inner mechanism of XYF therapy in psoriasis, which might promote its clinical application in psoriasis patients and facilitate the development of novel anti-psoriasis drugs based on the bioactive components of XYF.

Infliximab modifies regulatory T cells and co-inhibitory receptor expression on circulating T cells in psoriasis.

BACKGROUND: Psoriasis is a T cell-mediated autoimmune skin disease. Accumulating evidence has demonstrated that co-inhibitory receptors (CIRs) play a vital role in regulating T cell-mediated immune response, especially in neoplasm and autoimmunity. However, the immuno-function of CIRs in the development of psoriasis remains unclear. OBJECTIVE: We investigated the expression of CIRs on the circulating T lymphocytes of psoriasis patients before and after anti-tumor necrosis factor-α (TNF-α) therapy. METHODS: We enrolled 17 patients with moderate-to-severe plaque psoriasis, 17 patients with mild plaque psoriasis, and 18 healthy controls in this study. Fourteen of the moderate-to-severe psoriasis patients were treated with infliximab, a monoclonal antibody against TNF-α. Peripheral blood was collected, and peripheral blood mononuclear cells were extracted. The proportion of T cell subsets along with their expression of CIRs, namely T cell immunoreceptor with Ig and ITIM domains (TIGIT), lymphocyte activating gene 3 (LAG-3), cytotoxic T-lymphocyte associated protein 4 (CTLA-4), B and T lymphocyte-associated protein (BTLA), endothelial protein C receptor (PROCR), podoplanin (PDPN), programmed cell death 1 (PD-1), and T cell immunoglobulin mucin family containing molecule 3 (TIM-3), were determined by flow cytometric assay. RESULTS: The moderate-to-severe plaque psoriasis patients had less circulating Tregs, which increased after infliximab treatment. They also had decreased TIGIT, LAG-3 but increased PDPN expression on peripheral CD4+ T cells. Infliximab enhanced TIGIT, LAG-3, CTLA-4 but reduced PROCR expression on circulating CD4+ T cells. Remarkably, both the frequency of circulating Tregs and the expression level of TIGIT on CD4+ T cells at baseline (pre-treatment) negatively correlated with the extent of PASI score reduction benefited from infliximab therapy. CONCLUSION: Anti-TNF-α therapy increased the frequency of Tregs and TIGIT, LAG-3, CTLA-4 expression but reduced PROCR expression on circulating CD4+ T cells in psoriasis patients. The baseline proportion of Tregs and the expression level of TIGIT on circulating CD4+ T cells might serve as predictive markers for the degree of disease remission benefited from infliximab treatment.

Dysregulated Peripheral Invariant Natural Killer T Cells in Plaque Psoriasis Patients.

Background: Psoriasis is a common immune-mediated skin disease that involves T-cell-mediated immunity. Invariant natural killer T (iNKT) cells are a unique lymphocyte subpopulation that share properties and express surface markers of both NK cells and T cells. Previous reports indicate that iNKT cells regulate the development of various inflammatory diseases. IL-17 is a key cytokine in the pathogenesis of psoriasis and a key therapeutic target. Secukinumab is a fully human IgG1κ antibody that targets IL-17A, thereby antagonizing the biological effects of IL-17. Objective: To explore the expression of iNKT cells in psoriasis patients and the effect of secukinumab on them. Methods: We examined the frequencies of iNKT cells, Tregs, naïve and memory CD4+and CD8+T cells in the PBMCs as well as their cytokine production in a cohort of 40 patients with moderate-to-severe plaque psoriasis and 40 gender- and age-matched healthy controls. We further collected peripheral blood of another 15 moderate-to-severe plaque psoriasis patients who were treated with secukinumab and evaluated the proportion of iNKT cells in the PBMCs at baseline and week 12. Results: The frequencies of conventional CD4+ T cells, CD8+ T cells, and Tregs in the PBMCs were comparable between psoriasis patients and healthy controls, but the frequencies of Th17 cells, Tc1 cells and Tc17 cells were increased in psoriasis patients. The frequency of peripheral iNKT cells and CD69+ iNKT cells was significantly decreased in psoriasis patients. Both iNKT2 cells and iNKT17 cells were increased in psoriasis patients, but the ratio of iNKT2 cells vs iNKT17 cells was significantly reduced in psoriasis patients. After receiving secukinumab, the proportion of iNKT cells in the PBMCs of patients was increased, while the proportion of iNKT17 cells was decreased. Conclusion: Dysregulated iNKT cells may be involved in the pathogenesis of psoriasis and secukinumab may play a regulatory role on iNKT cells.

Decreased secretion and profibrotic activity of tubular exosomes in diabetic kidney disease.

Tubular changes contribute to the development of renal pathologies in diabetic kidney disease (DKD), including interstitial fibrosis. It is unclear how tubular cells relay signals to interstitial fibroblasts. Recently, exosomes have been recognized as crucial mediators of intercellular communication. We hypothesized that exosomes secreted from tubular cells may stimulate fibroblasts for interstitial fibrosis in DKD. In this study, we isolated and purified exosomes from the renal cortex of DKD mice and high glucose-treated mouse proximal tubular cells. Compared with nondiabetic mice, exosome secretion in kidney tissues decreased in DKD mice. Likewise, high glucose incubation reduced exosome secretion in mouse kidney proximal tubular BUMPT cells. To study the effect of tubular cell exosomes on fibroblasts, exosomes from BUMPT cells were added to renal fibroblast NRK-49F cell cultures. Notably, exosomes from high glucose conditioned BUMPT cells induced higher proliferation, significant morphological change, and substantial production of fibronectin, α-smooth muscle actin, and collagen type Ι in NRK-49F fibroblasts. Proteomics analysis was further performed to profile the proteins within tubular cell exosomes. Interestingly, 22 proteins were found to be differentially expressed between tubular exosomes derived from high glucose conditioned cells and those from normal glucose conditioned cells. Cytoscape analysis suggested the existence of two protein-protein interaction networks in these exosomal differentially expressed proteins. While one of the protein-protein interaction networks comprised enolase 1 (Eno1), heat shock protein family A member 8 (Hspa8), thioredoxin 1 (Txn1), peptidylprolyl isomerase A (Ppia), phosphoglycerate kinase 1 (Pgk1), DNA topoisomerase II-ß (Top2b), and ß-actin (Actb), the other had the family proteins of human leucocyte antigen F (Ywhag), a component of the ND10 nuclear body (Ywhae), interferon regulatory factor-8 (Ywhaq), and human leucocyte antigen A (Ywhaz). Gene expression analysis via Nephroseq showed a correlation of Eno1 expression with DKD clinical manifestation. In conclusion, DKD is associated with a decrease in exosome secretion in renal tubular cells. Exosomes from high glucose conditioned tubular cells may regulate the proliferation and activation of fibroblasts, contributing to the paracrine signaling mechanism responsible for the pathological onset of renal interstitial fibrosis in DKD.

High-throughput transcriptome and pathogenesis analysis of clinical psoriasis.

BACKGROUND: Previous psoriasis studies have mostly focused on skin-related immunology, but the exact mechanisms remain elusive. Clinical evidence, such as higher morbidity among obese individuals and emotional factors, indicate that psoriasis is a complex systemic disease. High-throughput transcriptome analysis provides an effective method to comprehensively assess the disease. OBJECTIVE: The present study is aiming to understand transcriptome changes of clinical psoriasis skins and comprehensively assess the diseases using pathways analysis. METHODS: We performed transcriptome sequence of clinical psoriatic samples. Biological pathway analyses were conducted using differentially expressed RNAs, as well as identified competing endogenous RNAs (ceRNAs). qRT-PCR and histological immunofluorescence staining was conducted to verify the differentially expressed RNAs (DE_RNAs) and the three important enriched biological pathways. RESULTS: Numerous DE_RNAs were identified between psoriasis patients and healthy people. Functional analysis indicated PPAR-fatty acids metabolism pathways, neural-hormone regulations, circadian entrainment were the three mostly appeared pathways. For PPAR-fatty acids metabolism pathways, the expression of seven randomly selected genes, including ACSBG1, ACOT2), CYP27A1, ELOVL3, FABP7, FADS2 and PPARG were all significantly decreased in psoriasis lesions. For neural-hormone regulation pathways, the expression of CFL1, EPHA2, HRAS were all significantly upregulated in psoriasis lesions. While the expression of four randomly selected genes from circadian entrainment pathways, including CRY2, PER3, NR1D1 and RORC were all significantly downregulated. Histological immunofluorescence staining of FADS2, EPHA2 and CRY2 were consistent with their genes' expressions. CONCLUSION: Our results revealed transcriptome changes of psoriasis, and indicated three important pathways involved in psoriasis, including PPAR-fatty acids metabolism pathways, neural-hormone regulations, circadian entrainment.

Epigenetic Regulation in Kidney Toxicity: Insights From Cisplatin Nephrotoxicity.

Nephrotoxicity, as a result of the exposure of kidney to endogenous and exogenous toxins, is an important factor for acute kidney injury and the development of progressive chronic kidney disease. Cisplatin is among the most widely studied kidney toxicants. In the past decade, epigenetic regulation has emerged as a notable pathogenic mechanism in cisplatin nephrotoxicity, including DNA methylation, histone modification, and noncoding RNAs. In this review, we use cisplatin nephrotoxicity as an example to highlight the epigenetic alteration, function, and underlying mechanism in kidney toxicity. The study of epigenetic regulation in kidney toxicity is still in its infancy, and further investigation will bring new insights for the development of novel diagnostic biomarkers and therapeutic interventions.

Epigenetic regulation in AKI and kidney repair: mechanisms and therapeutic implications.

Acute kidney injury (AKI) is a major public health concern associated with high morbidity and mortality. Despite decades of research, the pathogenesis of AKI remains incompletely understood and effective therapies are lacking. An increasing body of evidence suggests a role for epigenetic regulation in the process of AKI and kidney repair, involving remarkable changes in histone modifications, DNA methylation and the expression of various non-coding RNAs. For instance, increases in levels of histone acetylation seem to protect kidneys from AKI and promote kidney repair. AKI is also associated with changes in genome-wide and gene-specific DNA methylation; however, the role and regulation of DNA methylation in kidney injury and repair remains largely elusive. MicroRNAs have been studied quite extensively in AKI, and a plethora of specific microRNAs have been implicated in the pathogenesis of AKI. Emerging research suggests potential for microRNAs as novel diagnostic biomarkers of AKI. Further investigation into these epigenetic mechanisms will not only generate novel insights into the mechanisms of AKI and kidney repair but also might lead to new strategies for the diagnosis and therapy of this disease.

Endoplasmic reticulum stress in ischemic and nephrotoxic acute kidney injury.

Acute kidney injury (AKI) is a medical condition characterized by kidney damage with a rapid decline of renal function, which is associated with high mortality and morbidity. Recent research has further established an intimate relationship between AKI and chronic kidney disease. Perturbations of kidney cells in AKI result in the accumulation of unfolded and misfolded proteins in the endoplasmic reticulum (ER), leading to unfolded protein response (UPR) or ER stress. In this review, we analyze the role and regulation of ER stress in AKI triggered by renal ischemia-reperfusion and cisplatin nephrotoxicity. The balance between the two major components of UPR, the adaptive pathway and the apoptotic pathway, plays a critical role in determining the cell fate in ER stress. The adaptive pathway is evoked to attenuate translation, induce chaperones, maintain protein homeostasis and promote cell survival. Prolonged ER stress activates the apoptotic pathway, resulting in the elimination of dysfunctional cells. Therefore, regulating ER stress in kidney cells may provide a therapeutic target in AKI. KEY MESSAGES Perturbations of kidney cells in acute kidney injury result in the accumulation of unfolded and misfolded proteins in ER, leading to unfolded protein response (UPR) or ER stress. The balance between the adaptive pathway and the apoptotic pathway of UPR plays a critical role in determining the cell fate in ER stress. Modulation of ER stress in kidney cells may provide a therapeutic strategy for acute kidney injury.

Serum sclerostin in vascular calcification and clinical outcome in chronic kidney disease.

Sclerostin, a potent soluble inhibitor of the Wnt signalling pathway, is known to inhibit bone formation by suppressing osteocytes differentiation and function. Patients with chronic kidney disease have high levels of serum sclerostin. Sclerostin has been implicated in the pathogenesis of vascular calcification, which may promote the cardiovascular events of morbidity and mortality in chronic kidney disease patients. However, the role of sclerostin in vascular calcification and clinical prognosis in chronic kidney disease remains elusive. While some studies suggested a positive correlation between serum sclerostin and vascular calcification or clinical outcome, other studies showed no or even negative correlation between them. Small sample size, heterogeneity in enrolled patients, discrepancy in anatomical structure examined and differences in the applied assays may be responsible for the discrepant results. Nonetheless, anti-sclerostin antibodies may be a new therapeutic approach to increase bone mass and strength in chronic kidney disease. This review aims to have a better understanding of the relationship of serum sclerostin with vascular calcification and clinical outcome in chronic kidney disease patients, and propose the application of anti-sclerostin therapy in chronic kidney disease.