Histone deacetylase inhibitors attenuate P-aIgA1-induced cell proliferation and extracellular matrix synthesis in human renal mesangial cells in vitro

Huanglian Decoction treats Henoch-Schonlein purpura nephritis by inhibiting NF-κB/NLRP3 signaling pathway and reducing renal IgA deposition

Henoch-Schonlein purpura nephritis (HSPN) is a systemic vascular inflammatory disease. Huanglian Decoction (HLD) ameliorates renal injury in nephritis; however, the mechanism of action of HLD on HSPN has not been investigated. This study aimed to investigate the protective mechanism of HLD treatment in HSPN. The effects of HLD on HSPN biochemical indices, kidney injury and NF-κB/NLRP3 signaling pathway were analyzed by biochemical analysis, ELISA, HE and PAS staining, immunohistochemistry, immunofluorescence, and Western Blot. In addition, the effects of HLD on HSPN cells were analyzed. We found that HLD treatment significantly reduced renal tissue damage, decreased the levels of IL-17, IL-18, TNF-α, and IL-1β, and increased the levels of TP and ALB in HSPN mice. It also inhibited the deposition of IgA, IgG, and C3 in kidney tissues and significantly decreased the expression of IκBα, p-IκBα, NLRP3, caspase-1, and IL-1β in kidney tissues and cells. In addition, PMA treatment inhibited the above-mentioned effects of HLD. These results suggested that HLD attenuates renal injury, IgA deposition, and inflammation in HSPN mice and its mechanism of action may be related to the inhibition of the NF-κB/NLRP3 pathway.

Epigenetic Regulation of EMP/EMT-Dependent Fibrosis

Fibrosis represents a process characterized by excessive deposition of extracellular matrix (ECM) proteins. It often represents the evolution of pathological conditions, causes organ failure, and can, in extreme cases, compromise the functionality of organs to the point of causing death. In recent years, considerable efforts have been made to understand the molecular mechanisms underlying fibrotic evolution and to identify possible therapeutic strategies. Great interest has been aroused by the discovery of a molecular association between epithelial to mesenchymal plasticity (EMP), in particular epithelial to mesenchymal transition (EMT), and fibrogenesis, which has led to the identification of complex molecular mechanisms closely interconnected with each other, which could explain EMT-dependent fibrosis. However, the result remains unsatisfactory from a therapeutic point of view. In recent years, advances in epigenetics, based on chromatin remodeling through various histone modifications or through the intervention of non-coding RNAs (ncRNAs), have provided more information on the fibrotic process, and this could represent a promising path forward for the identification of innovative therapeutic strategies for organ fibrosis. In this review, we summarize current research on epigenetic mechanisms involved in organ fibrosis, with a focus on epigenetic regulation of EMP/EMT-dependent fibrosis.

Molecular insight in intrarenal inflammation affecting four main types of cells in nephrons in IgA nephropathy

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis and the leading cause of kidney failure in the world. The current widely accepted framework for its pathogenesis is the "multi-hit hypothesis." In this review, we mainly discussed the intrarenal inflammation in IgAN, which is initiated by immune complex deposition with complement molecule activation, by focusing on four main types of cells in nephrons including mesangial cells, endothelial cells, podocytes, and tubular epithelial cells (TECs). Galactose-deficient IgA1 (Gd-IgA1)-containing immune complexes deposit in the mesangium and activate complement molecules and mesangial cells. Activation of mesangial cells by Gd-IgA1 deposition with enhanced cellular proliferation, extracellular matrix (ECM) expansion, and inflammatory response plays a central role in the pathogenesis of IgAN. Regional immune complex deposition and mesangial-endothelial crosstalk result in hyperpermeability of endothelium with loss of endothelial cells and infiltration barrier proteins, and recruitment of inflammatory cells. Podocyte damage is mainly derived from mesangial-podocyte crosstalk, in which tumor necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β), renin-angiotensin-aldosterone system (RAAS), and micro-RNAs are the major players in podocyte apoptosis and disorganization of slit diaphragm (SD) related to proteinuria in patients with IgAN. In addition to filtrated proteins into tubulointerstitium and mesangial-tubular crosstalk involved in the injury of TECs, retinoic acid has been discovered innovatively participating in TEC injury.

Identification of key cuproptosis-related genes and their targets in patients with IgAN

BACKGROUND

IgA nephropathy (IgAN) is one of the most common forms of chronic glomerulonephritis, but the aetiology and pathogenesis remain unclear. Cuproptosis is a newly identified form of cell death that plays an important role in many diseases. Researchers have not clearly determined whether the expression of cuproptosis-related genes (CRGs) is involved in the pathogenesis of IgAN.

METHODS

The GSE93798, GSE50469 and GSE37460 datasets containing microarray data from patients with IgAN (63) and healthy controls (31) were downloaded from the GEO database. Immune cells and immune-related functions were analysed in patients with IgAN and controls, and genes were identified that may be related to cuproptosis. A logistic regression model was established according to the results, and then GO and KEGG enrichment analyses were performed. Finally, possible drugs were selected using the DSigDB database.

RESULTS

The subjects in the different groups showed significantly different fractions of immune cells and immune-related functions, and 11 genes related to cuproptosis may be involved in these processes. Based on these 11 genes, the ROC curve was plotted, and the AUC value was calculated (0.898, 95% CI: 0.839-0.958). The result revealed good predictability. Then, genes with P < 0.05 (lipoyltransferase 1, LIPT1) were selected to plot an ROC curve, and the AUC value was calculated (0.729, 95% CI: 0.636-0.821). Enrichment analyses showed that the TCA cycle and multiple metabolic pathways may also be involved in the occurrence of IgAN. Finally, 293 potential drugs that may be used to treat IgAN were identified based on these genes.

CONCLUSION

In this study, we identified some novel CRGs that may be involved in IgAN, among which LIPT1 was significantly differentially expressed. It may predict the risk of IgAN and provides a possible target for the treatment of IgAN. Further experimental studies are needed to explore how these CRGs mediate the occurrence and development of IgAN.

Molecular mechanisms of histone deacetylases and inhibitors in renal fibrosis progression

Renal fibrosis is a common progressive manifestation of chronic kidney disease. This phenomenon of self-repair in response to kidney damage seriously affects the normal filtration function of the kidney. Yet, there are no specific treatments for the condition, which marks fibrosis as an irreversible pathological sequela. As such, there is a pressing need to improve our understanding of how fibrosis develops at the cellular and molecular levels and explore specific targeted therapies for these pathogenic mechanisms. It is now generally accepted that renal fibrosis is a pathological transition mediated by extracellular matrix (ECM) deposition, abnormal activation of myofibroblasts, and epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells under the regulation of TGF-β. Histone deacetylases (HDACs) appear to play an essential role in promoting renal fibrosis through non-histone epigenetic modifications. In this review, we summarize the mechanisms of renal fibrosis and the signaling pathways that might be involved in HDACs in renal fibrosis, and the specific mechanisms of action of various HDAC inhibitors (HDACi) in the anti-fibrotic process to elucidate HDACi as a novel therapeutic tool to slow down the progression of renal fibrosis.

Histone Acetylation and Modifiers in Renal Fibrosis

Histones are the most abundant proteins bound to DNA in eukaryotic cells and frequently subjected to post-modifications such as acetylation, methylation, phosphorylation and ubiquitination. Many studies have shown that histone modifications, especially histone acetylation, play an important role in the development and progression of renal fibrosis. Histone acetylation is regulated by three families of proteins, including histone acetyltransferases (HATs), histone deacetylases (HDACs) and bromodomain and extraterminal (BET) proteins. These acetylation modifiers are involved in a variety of pathophysiological processes leading to the development of renal fibrosis, including partial epithelial-mesenchymal transition, renal fibroblast activation, inflammatory response, and the expression of pro-fibrosis factors. In this review, we summarize the role and regulatory mechanisms of HATs, HDACs and BET proteins in renal fibrosis and provide evidence for targeting these modifiers to treat various chronic fibrotic kidney diseases in animal models.

miR-136 Suppresses the Aggressive Proliferation of Non-Small Cell Lung Cancer Through Restraining Histone Deacetylase 1 (HDAC1) and Phosphorylation of the Janus Kinase 2/Signal Transducer and Activator of Transcription 3 (Jak2/STAT3) Pathway

microRNA-136 can inhibit the proliferating activity of malignant cells and also participate in chemotherapy resistance of colorectal cancer via modulating HDAC1. This study assessed miR-136’s effect on NSCLC cell proliferation and underlying mechanisms. Tumor tissues and paracancerous tissues from NSCLC patients were collected to measure miR-136 and HDAC1 level. Cells were transfected with miR-136-mimics, miR-136-inhibitors or miR-136 mimics+HDAC1-OE followed by analysis of cell viability and apoptosis by CCK-8 method and flow cytometry, phosphorylation of Jak2/STAT3 by western blot. miR-136 was significantly downregulated in tumor tissues and NSCLC cells, accompanied by upregulated HDAC1. miR-136 overexpression suppressed HDAC1 expression, retarded phosphorylation and activation of Jak2/STAT3 signaling, reduced NSCLC cell viability and enhanced apoptosis. In addition, co-transfection of miR-136-mimics and HDAC1-OE reversed the inhibitory effects of miR-136 on NSCLC cells. In conclusion, miR-136 is reduced and HDAC1 is increased in NSCLC and miR-136 overexpression inhibited NSCLC cell proliferation and increased apoptosis possibly through regulating HDAC1/Jak2/STAT3 signal pathway, indicating that miR-136 might be a novel target for the treatment of NSCLC.

TRIM40 inhibits IgA1-induced proliferation of glomerular mesangial cells by inactivating NLRP3 inflammasome through ubiquitination

IgA nephropathy, as the most common type of glomerulonephritis, causes chronic renal disease and progresses into kidney failure. Aberrant IgA deposition in the glomerular mesangium induces NLRP3 inflammasome activation for massive local inflammation, and is recognized as the primary pathogenesis in IgA nephropathy. Tripartite motif (TRIM)-containing proteins are E3 ubiquitin ligases that possess crucial regulatory functions in innate immunity, but their functional roles in IgA nephropathy are still unclear. Here, we aimed to identify TRIM-containing proteins that regulate IgA nephropathy and their underlying mechanisms. An in vitro IgA1-induction model was established in glomerular mesangial cells (GMCs) and showed that IgA1 could promote GMC proliferation by activating NLRP3 inflammasome. TRIM40, which was downregulated by IgA1 and interacted with NLRP3, was recognized as a promising candidate. In addition, TRIM40 could suppress IgA1-induced GMC proliferation by inhibiting the activation of NLRP3 inflammasome. Based on coimmunoprecipitation and ubiquitination assays, we confirmed that TRIM40 could mediate the ubiquitination of NLRP3, which explained its regulatory effects on NLRP3 inflammasome and GMC proliferation. More importantly, a dominant-negative mutant of TRIM40 lacking the RING domain (ΔRING) did not affect NLRP3 ubiquitination, and had no effects on IgA1-induced GMC proliferation or NLRP3 inflammasome activation. This study revealed the biological functions of TRIM40 in IgA nephropathy, facilitating its application as therapeutic target for IgA nephropathy and other NLRP3 inflammasome-relevant diseases.

Reduced fecal short-chain fatty acids levels and the relationship with gut microbiota in IgA nephropathy

BACKGROUND

IgA nephropathy(IgAN)) is the common pathological type of glomerular diseases. The role of gut microbiota in mediating "gut-IgA nephropathy" has not received sufficient attention in the previous studies. The purpose of this study was to investigate the changes of fecal short-chain fatty acids(SCFAs), a metabolite of the intestinal microbiota, in patients with IgAN and its correlation with intestinal flora and clinical indicators, and to further investigate the role of the gut-renal axis in IgAN.

METHODS

There were 29 patients with IgAN and 29 normal control subjects recruited from January 2018 to May 2018. The fresh feces were collected. The fecal SCFAs were measured by gas chromatography/mass spectrometry and gut microbiota was analysed by16S rDNA sequences, followed by estimation of α- and β-diversity. Correlation analysis was performed using the spearman's correlation test between SCFAs and gut microbiota.

RESULTS

The levels of acetic acid, propionic acid, butyric acid, isobutyric acid and caproic acid in the IgAN patients were significantly reduced compared with control group(P < 0.05). Butyric acid(r=-0.336, P = 0.010) and isobutyric acid(r=-0.298, P = 0.022) were negatively correlated with urea acid; butyric acid(r=-0.316, P = 0.016) was negatively correlated with urea nitrogen; caproic acid(r=-0.415,P = 0.025) showed negative correlation with 24-h urine protein level.Exemplified by the results of α-diversity and β-diversity, the intestinal flora of IgAN patients was significantly different from that of the control group. Acetic acid was positively associated with c_Clostridia(r = 0.357, P = 0.008), o_Clostridiales(r = 0.357, P = 0.008) and g_Eubacterium_coprostanoligenes_group(r = 0.283, P = 0.036). Butyric acid was positively associated with g_Alistipes (r = 0.278, P = 0.040). The relative abundance of those were significantly decreased in IgAN group compared to control group.

CONCLUSIONS

The levels of fecal SCFAs in the IgAN patients were reduced, and correlated with clinical parameters and gut microbiota, which may be involved in the pathogenesis of IgAN, and this finding may provide a new therapeutic approach.

Application of Histone Deacetylase Inhibitors in Renal Interstitial Fibrosis

BACKGROUND

Renal interstitial fibrosis is characterized by the accumulation of extracellular matrix proteins, which is a common feature of chronic kidney diseases.

SUMMARY

Increasing evidence has shown the aberrant expression of histone deacetylases (HDACs) in the development and progression of renal fibrosis, suggesting the possibility of utilizing HDAC inhibitor (HDACi) as therapeutics for renal fibrosis. Recent studies have successfully demonstrated the antifibrotic effects of HDACis in various animal models, which are associated with multiple signaling pathways including TGF-β signaling, EGRF signaling, signal transducer and activator of transcription 3 pathway, and JNK/Notch2 signaling. This review will focus on the utilization of HDACi as antifibrotic agents and its relative molecular mechanisms.

KEY MESSAGES

HDACis have shown promising results in antifibrotic therapy, and it is rational to anticipate that HDACis will improve clinical outcomes of renal fibrosis in the future.

Mesangial Cells and Renal Fibrosis

The main cellular constituents in glomerular mesangium are mesangial cells, which account for approximately 30-40% of the total cells in the glomerulus. Together with the mesangial matrix, mesangial cells form the glomerular basement membrane (GBM) in the glomerulus, whose main function is to perform the filtration. Under the pathologic conditions, mesangial cells are activated, leading to hyperproliferation and excess extracellular matrix (ECM). Moreover, mesangial cells also secrete several kinds of inflammatory cytokines, adhesion molecules, chemokines, and enzymes, all of which participate in the process of renal glomerular fibrosis. During the past years, researchers have revealed the roles of mesangial cells and the associated signal pathways involved in renal fibrosis. In this section, we will discuss how mesangial cells are activated and its contributions to renal fibrosis, as well as the molecular mechanisms and novel anti-fibrotic agents. Full understanding of the contributions of mesangial cells to renal fibrosis will benefit the clinical drug developing.

Triptolide protects podocytes via autophagy in immunoglobulin A nephropathy

Triptolide is often used to treat patients with immunoglobulin A nephropathy (IgAN), especially in Asia. However, its detailed mechanism remains unclear. In vitro experiments were conducted with podocytes exposed to aggregated IgA (aIgA)-MSC1097-conditioned media. A total of four groups were compared in this study: A control group (CON); a healthy supernatant group (HEAs); an IgAN supernatant group (IgANs); and a triptolide group (TRI). First, aggregated IgA1 (aIgA1) was generated by heating monomeric IgA1 (mIgA1) from IgAN patients or healthy subjects. Next, the conditioned supernatant of MSC-1097 cells cultured with aIgA1 (100 mg/l) from IgAN patients (IgANs) or healthy subjects (HEAs) or without aIgA1 (CON) were harvested and used to incubate MPC5 cells. MPC5 cells in the TRI group were cultured with triptolide (10 ng/ml) and conditioned media from MSC-1097 cells cultured with aIgA1 from IgAN patients. After 24 h of treatment, MPC5 cells were collected to measure autophagy-related protein levels, including microtubule-associated protein light chain 3 (LC3), p62, cluster of differentiation (CD)63, phosphorylated-protein kinase B (Akt), Akt, p-mammalian target of rapamycin (mTOR), and mTOR, via western blotting, immunofluorescence or both, and to determine apoptosis by flow cytometry. All the results showed no difference between the CON and the HEAs. Compared to the CON and the HEAs, MPC5 cells in the IgANs group showed reduced autophagy, which was presented as decreased levels of LC3-II and CD63, as well as accumulation of p62, and an increased podocyte apoptosis rate. This was partly rescued by the addition of triptolide. Moreover, the p-mTOR/mTOR ratio increased in the IgANs group and decreased in the TRI group. Therefore, these results suggest that triptolide protects podocyte autophagy in IgAN patients.

Therapeutic effects of histone deacetylase inhibitors on kidney disease

Increasing evidence has shown the involvement of histone deacetylases (HDACs) in the development and progression of various renal diseases, highlighting its inhibition as a promising therapeutic strategy to prevent kidney diseases. Accordingly, numerous studies have shown that HDAC inhibitors protect the kidneys from various diseases through their effects on multiple pathways, such as suppression of transforming growth factor-β signaling pathway and nuclear factor-κB signaling pathways, augmentation of apoptosis, and inhibition of angiogenesis. To develop more effective and less toxic isoform-selective HDAC inhibitors and further improve clinical outcomes, it is necessary to identify and understand the mechanisms involved in the pathogenesis and progression of renal diseases. This review focuses on the roles of HDAC inhibitors and the mechanisms involved in their therapeutic effects in experimental models of kidney diseases including glomerulosclerosis, tubulointerstitial fibrosis, glomerular and tubulointerstitial inflammation, lupus nephritis, polycystic kidney disease, and renal cell carcinoma (RCC).

Anti-fibrotic effects of valproic acid: role of HDAC inhibition and associated mechanisms

Tissue injuries and pathological insults produce oxidative stress, genetic and epigenetic alterations, which lead to an imbalance between pro- and anti-fibrotic molecules, and subsequent accumulation of extracellular matrix, thereby fibrosis. Various molecular pathways play a critical role in fibroblasts activation, which promotes the extracellular matrix production and accumulation. Recent reports highlighted that histone deacetylases (HDACs) are upregulated in various fibrotic disorders and play a central role in fibrosis, while HDAC inhibitors exert antifibrotic effects. Valproic acid is a first-line anti-epileptic drug and a proven HDAC inhibitor. This review provides the current research and novel insights on antifibrotic effects of valproic acid in various fibrotic conditions with an emphasis on the possible strategies for treatment of fibrosis.