A Pathogenic Role for c-Jun Amino-Terminal Kinase Signaling in Renal Fibrosis and Tubular Cell Apoptosis

Y-27632 enables long-term expansion of mouse submandibular gland epithelial cells via inactivation of TGF-β1/CTGF/p38 and ROCK2/JNK signaling pathway

OBJECTIVES

This study aimed to investigate the effects of Y-27632 on the long-term maintainence of mouse submandibular epithelial cells (SG-Epis) in vitro and to elucidate the underlying mechanisms.

METHODS

The role of the Rho-associated kinase (ROCK) inhibitor Y-27632 in maintaining SG-Epis and its underlying mechanisms were evaluated by examining the in vitro expansion of mouse SG-Epis. Changes in key cellular characteristics, such as proliferation, long-term expansion, and mRNA and protein expression, were assessed in the presence or absence of Y-27632.

RESULTS

Treatment with Y-27632 significantly enhanced the proliferative potential of SG-Epis, preserving Krt8 and Krt14 expression over 17 passages. In the absence of Y-27632, SG-Epis lost their epithelial morphology. However, Y-27632 treatment maintained the epithelial morphology and downregulated mRNA levels of Tgf-β1, Ctgf, and Rock2. Treatment with TGF-β1 indicated that TGF-β/CTGF/p38 signaling is responsible for the maintenance of SG-Epis, while RNA interference studies revealed that ROCK2/c-Jun N-terminal kinase (JNK) signaling is also crucial for SG-Epis proliferation and maintenance.

CONCLUSIONS

The TGF-β1/CTGF/p38 and ROCK2/JNK signaling pathways are responsible for SG-Epis proliferation, and Y-27632 treatment effectively inactivates these pathways, enabling long-term in vitro maintenance of SG-Epis. The culture method utilizing Y-27632 provides an effective approach for the in vitro expansion of SG-Epis.

β-Mangostin Alleviates Renal Tubulointerstitial Fibrosis via the TGF-β1/JNK Signaling Pathway

The epithelial-to-mesenchymal transition (EMT) plays a key role in the pathogenesis of kidney fibrosis, and kidney fibrosis is associated with an adverse renal prognosis. Beta-mangostin (β-Mag) is a xanthone derivative obtained from mangosteens that is involved in the generation of antifibrotic and anti-oxidation effects. The purpose of this study was to examine the effects of β-Mag on renal tubulointerstitial fibrosis both in vivo and in vitro and the corresponding mechanisms involved. As shown through an in vivo study conducted on a unilateral ureteral obstruction mouse model, oral β-Mag administration, in a dose-dependent manner, caused a lesser degree of tubulointerstitial damage, diminished collagen I fiber deposition, and the depressed expression of fibrotic markers (collagen I, α-SMA) and EMT markers (N-cadherin, Vimentin, Snail, and Slug) in the UUO kidney tissues. The in vitro part of this research revealed that β-Mag, when co-treated with transforming growth factor-β1 (TGF-β1), decreased cell motility and downregulated the EMT (in relation to Vimentin, Snail, and N-cadherin) and phosphoryl-JNK1/2/Smad2/Smad3 expression. Furthermore, β-Mag co-treated with SB (Smad2/3 kinase inhibitor) or SP600125 (JNK kinase inhibitor) significantly inhibited the TGF-β1-associated downstream phosphorylation and activation of JNK1/2-mediated Smad2 targeting the Snail/Vimentin axis. To conclude, β-Mag protects against EMT and kidney fibrotic processes by mediating the TGF-β1/JNK/Smad2 targeting Snail-mediated Vimentin expression and may have therapeutic implications for renal tubulointerstitial fibrosis.

ORAI2 is Important for the Development of Early-Stage Postirradiation Fibrosis in Salivary Glands

PURPOSE

Although postirradiation hyposalivation significantly impairs patient quality of life, the underlying mechanisms driving radiation-induced salivary gland fibrosis and hyposalivation remain poorly understood. This study aims to explore the role of calcium-mediated signaling pathways in radiation-induced salivary gland fibrosis.

METHODS AND MATERIALS

Primary human submandibular gland (SG) cells and C57BL/6J female mouse SGs were exposed to irradiation to model fibrosis development. Following 15 Gy irradiation exposure, RNA sequencing and bioinformatic analysis were conducted on mouse SGs. The effects of store-operated calcium entry (SOCE) inhibition using SKF96365 and YM58483 on fibrosis markers were assessed in vitro and in vivo. Additionally, the involvement of ORAI2 protein and the newly identified JNK/NFAT1/transforming growth factor β1 (TGF-β1) signaling axis in SG fibrosis was explored.

RESULTS

We identified that the calcium release-activated calcium modulator ORAI2 was important in promoting early-stage postirradiation fibrosis in SGs. Calcium channel signaling was activated in both human patients and irradiated C57BL/6J female mice SGs. Inhibition of SOCE signaling effectively blocked fibrosis in an ORAI2-dependent manner 30 days after irradiation. Our mechanistic studies revealed a novel ORAI2/JNK/NFAT1 axis within the SOCE pathway critical in driving TGF-β1-mediated fibrogenesis. Encouragingly, pharmacologic inhibition of NFAT1 significantly mitigated radiation-induced SG fibrosis and restored saliva flow to 84.61% of normal levels in treated mice 30 days after irradiation, without detectable side effects.

CONCLUSIONS

Our findings highlight the significance of the ORAI2-mediated calcium signaling pathway, specifically via the ORAI2/JNK/NFAT1 axis, in promoting TGF-β1 expression and contributing to the development of early-stage salivary gland fibrosis following irradiation exposure. Targeting the ORAI2/JNK/NFAT1 axis emerges as a promising therapeutic strategy to alleviate radiation-induced hyposalivation and fibrosis, potentially improving the quality of life for patients undergoing radiation therapy.

Update on JNK inhibitor patents: 2015 to present

INTRODUCTION

c-Jun N-terminal kinase (JNK) regulates various biological processes through the phosphorylation cascade and is closely associated with numerous diseases, including inflammation, cardiovascular diseases, and neurological disorders. Therefore, JNKs have emerged as potential targets for disease treatment.

AREAS COVERED

This review compiles the patents and literatures concerning JNK inhibitors through retrieving relevant information from the SciFinder, Google Patents databases, and PubMed from 2015 to the present. It summarizes the structure-activity relationship (SAR) and biological activity profiles of JNK inhibitors, offering valuable perspectives on their potential therapeutic applications.

EXPERT OPINION

The JNK kinase serves as a novel target for the treatment of neurodegenerative disorders, pulmonary fibrosis, and other illnesses. A variety of small-molecule inhibitors targeting JNKs have demonstrated promising therapeutic potential in preclinical studies, which act upon JNK kinases via distinct mechanisms, encompassing traditional ATP competitive inhibition, covalent inhibition, and bidentate inhibition. Among them, several JNK inhibitors from PregLem SA, Celegene SA, and Xigen SA have accomplished the early stage of clinical trials, and their results will guide the development and indications of future JNK inhibitors.

Therapeutic approaches and novel antifibrotic agents in renal fibrosis: A comprehensive review

Renal fibrosis (RF) is one of the underlying pathological conditions leading to progressive loss of renal function and end-stage renal disease (ESRD). Over the years, various therapeutic approaches have been explored to combat RF and prevent ESRD. Despite significant advances in understanding the underlying molecular mechanism(s), effective therapeutic interventions for RF are limited. Current therapeutic strategies primarily target these underlying mechanisms to halt or reverse fibrotic progression. Inhibition of transforming growth factor-β (TGF-β) signaling, a pivotal mediator of RF has emerged as a central strategy to manage RF. Small molecules, peptides, and monoclonal antibodies that target TGF-β receptors or downstream effectors have demonstrated potential in preclinical models. Modulating the renin-angiotensin system and targeting the endothelin system also provide established approaches for controlling fibrosis-related hemodynamic changes. Complementary to pharmacological strategies, lifestyle modifications, and dietary interventions contribute to holistic management. This comprehensive review aims to summarize the underlying mechanisms of RF and provide an overview of the therapeutic strategies and novel antifibrotic agents that hold promise in its treatment.

Intervention treatment reducing cellular senescence inhibits tubulointerstitial fibrosis in diabetic mice following acute kidney injury

Senescence of kidney tubules leads to tubulointerstitial fibrosis (TIF). Proximal tubular epithelial cells undergo stress-induced senescence during diabetes and episodes of acute kidney injury (AKI), and combining these injuries promotes the progression of diabetic kidney disease (DKD). Since TIF is crucial to progression of DKD, we examined the therapeutic potential of targeting senescence with a senolytic drug (HSP90 inhibitor) and/or a senostatic drug (ASK1 inhibitor) in a model of TIF in which AKI is superimposed on diabetes. After 8 weeks of streptozotocin-induced diabetes, mice underwent bilateral clamping of renal pedicles to induce mild AKI, followed by 28 days of reperfusion. Groups of mice (n=10-12) received either vehicle, HSP90 inhibitor (alvespimycin), ASK1 inhibitor (GS-444217), or both treatments. Vehicle-treated mice displayed tubular injury at day 3 and extensive tubular cell senescence at day 10, which remained unresolved at day 28. Markers of senescence (Cdkn1a and Cdkn2a), inflammation (Cd68, Tnf, and Ccl2), and TIF (Col1a1, Col4a3, α-Sma/Acta2, and Tgfb1) were elevated at day 28, coinciding with renal function impairment. Treatment with alvespimycin alone reduced kidney senescence and levels of Col1a1, Acta2, Tgfb1, and Cd68; however, further treatment with GS-444217 also reduced Col4a3, Tnf, Ccl2, and renal function impairment. Senolytic therapy can inhibit TIF during DKD, but its effectiveness can be improved by follow-up treatment with a senostatic inhibitor, which has important implications for treating progressive DKD.

QiDiTangShen granules alleviates diabetic nephropathy podocyte injury: A network pharmacology study and experimental validation in vivo and vitro

Background

QiDiTangShen granules (QDTS), a traditional Chinese medicine (TCM) compound prescription, have remarkable efficacy in diabetic nephropathy (DN) patients, and their pharmacological mechanism needs further exploration.

Methods

According to the active ingredients and targets of the QDTS in the TCMSP database, the network pharmacology of QDTS was investigated. The potential active ingredients were chosen based on the oral bioavailability and the drug similarity index. At the same time, targets for DN-related disease were obtained from GeneCards, OMIM, PharmGKB, TTD, and DrugBank. The TCM-component-target network and the protein-protein interaction (PPI) network were constructed with the Cytoscape and STRING platforms, respectively, and then the core targets of DN were selected with CytoNCA. GO and KEGG enrichment analysis using R software. Molecular docking to identify the core targets of QDTS for DN. In vivo, db/db mice were treated as DN models, and the urine microalbuminuria, the pathological changes in the kidney and the protein expression levels of p-PI3K, p-Akt, JUN, nephrin and synaptopodin were detected by immunohistochemistry, immunofluorescence method and Western blotting. After QDTS was used in vitro, the protein expression of mouse podocyte clone-5 (MPC5) cells was detected by immunohistochemistry, immunofluorescence and Western blot.

Results

Through network pharmacology analysis, 153 potential targets for DN in QDTS were identified, 19 of which were significant. The KEGG enrichment analysis indicated that QDTS might have therapeutic effects on IL-17, TNF, AGE-RAGE, PI3K-Akt, HIF-1, and EGFR through interfering with Akt1 and JUN. The main active ingredients in QDTS are quercetin, β-sitosterol, stigmasterol and kaempferol. Both in vivo and in vitro studies showed that QDTS could decrease the urine microalbuminuria and renal pathology of db/db mice, and alleviate podocyte injuries through the PI3K/Akt signaling pathway.

Conclusion

Through network pharmacology, in vivo and in vitro experiments, QDTS has been shown to improve the urine microalbuminuria and renal pathology in DN, and to reduce podocyte damage via the PI3K/Akt pathway.

Rehmannia glutinosa Libosch and Cornus officinalis Sieb herb couple ameliorates renal interstitial fibrosis in CKD rats by inhibiting the TGF-β1/MAPK signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Herb couple Rehmannia glutinosa Libosch and Cornus officinalis Sieb (RC), originated from "Liuwei Dihuang Pill" which recorded in Key to Therapeutics of Children's Diseases. Traditionally, they have been used widely for their ability to nourish yin and energize the kidneys. Our previous study indicated that the RC could protect against adenine induced Chronic kidney disease (CKD) rats. Nevertheless, there is still no clear explanation of the mechanisms by which RC affects renal interstitial fibrosis in CKD rats.

AIM OF THE STUDY

Current Work aims to explore the amelioration and potential mechanism of RC on renal interstitial fibrosis in CKD rats.

MATERIALS AND METHODS

CKD rats were induced by adenine. Two weeks after administration, blood, urine, and kidney tissue were collected for biochemical analysis. Observing the physiological state of rats through the changes of rat body weight and renal index. The pro-inflammatory cytokines were measured by enzyme linked immunosorbent assay (ELISA), while renal tissue damage and fibrosis were assessed with Hematoxylin-eosin staining (H&E) and Masson's trichrome staining. In order to determine the levels of indicators and proteins associated with fibrosis signaling pathways, real time PCR (Rt-PCR), Western blot (WB), and immunofluorescence were employed.

RESULTS

The renal interstitial fibrosis led to impaired cellular functions with increased the levels of Blood Urea Nitrogen (BUN), Urine protein (UP), Interleukin-1β (IL-1β), Interleukin-6 (IL-6), and Tumor Necrosis Factor alpha (TNF-α). and simultaneous up-regulated collagenⅠ(COL-1), fibronection (FN), α-smooth muscle actin (a-SMA), transforming growth factor-β1 (TGF-β1), c-Jun N-terminal kinase (JNK), p38 and extracellular regulated protein kinases (ERK), down-regulated the expression of the E-cadherin proteins. RC notably improved renal dysfunction in CKD rats as indicated by decreases in BUN, UP, and renal index. In addition, consistent with the morphological changes of renal tissue, renal interstitial fibrosis in CKD rats after RC intervention was significantly improved, mainly manifested by a decrease in the positive expression of COL-1, FN, and a-SMA, and increased levels of E-cadherin protein. Meanwhile, RC reduced the classical pro-inflammatory cytokines IL-1β, IL-6, and TNF-α in adenine-induced CKD rats. Additionally, RC administration also down-regulated TGF-β1, JNK, p38 and ERK.

CONCLUSION

In conclusion, RC may reduce inflammation in adenine induced CKD rats, improve extracellular matrix (ECM) components deposition, and diminish epithelial-mesenchymal transition (EMT) marker protein levels. Furthermore, RC intervention significantly reduces the release of inflammatory cytokines and inhibits the TGF-β1/MAPK signaling pathway. Based on the results, RC might be useful in the treatment of adenine induced renal fibrosis.

A gradient model of renal ischemia reperfusion injury to investigate renal interstitial fibrosis

Background: The progression from acute kidney injury to chronic kidney disease poses a significant health challenge. Nonetheless, a constraint in existing animal models of renal ischemia/reperfusion (I/R) injury is the necessity for a severe injury, almost reaching a life-threatening level, to trigger the subsequent onset of renal fibrosis. Hence, we explored an adapted gradient approach to induce I/R injury, aiming to promote the progression of renal fibrosis while preserving the overall normal functioning of the kidney. Methods: In each group, 6-8 male C57BL/6 mice were used for model construction, with all undergoing sodium pentobarbital anesthesia and left kidney removal. Subsequently, a silk thread was passed beneath the lower renal branch, elevating the right kidney under a 20-g weight's tension via a pulley system for durations of 30, 40, or 60 min. Afterwards, we lowered the kidney, sutured the wound, and administered intraperitoneal saline. Mice in different groups were euthanized following reperfusion for 1, 3, 7, or 28 days. Results: We observed a complete cessation of blood flow in the lower pole, while an incomplete cessation in the upper pole in the elevated kidney. Significant renal impairment was evident on day 1 with a 60min ischemic period (187.0 ± 65.3 vs 17.9 ± 4.8 μmol/L serum creatinine in normal; p < .001), but not with 30 or 40min. On day 1, tubular necrosis and hyaline cast formation was evident in both lower and upper poles. On day 3, renal function returned to normal and remained normal through day 28. Histologic damage resolved in the upper pole over days 3 to 7, resulting in normal histology on day 28. By contrast, there was sustained tubular damage tubular in the lower pole on days 3 and 7, which failed to resolve and led to significant renal fibrosis by day 28. Conclusion: We created a model demonstrating clinically "silent" renal fibrosis.

Natural products in traditional Chinese medicine: molecular mechanisms and therapeutic targets of renal fibrosis and state-of-the-art drug delivery systems

Renal fibrosis (RF) is the end stage of several chronic kidney diseases. Its series of changes include excessive accumulation of extracellular matrix, epithelial-mesenchymal transition (EMT) of renal tubular cells, fibroblast activation, immune cell infiltration, and renal cell apoptosis. RF can eventually lead to renal dysfunction or even renal failure. A large body of evidence suggests that natural products in traditional Chinese medicine (TCM) have great potential for treating RF. In this article, we first describe the recent advances in RF treatment by several natural products and clarify their mechanisms of action. They can ameliorate the RF disease phenotype, which includes apoptosis, endoplasmic reticulum stress, and EMT, by affecting relevant signaling pathways and molecular targets, thereby delaying or reversing fibrosis. We also present the roles of nanodrug delivery systems, which have been explored to address the drawback of low oral bioavailability of natural products. This may provide new ideas for using natural products for RF treatment. Finally, we provide new insights into the clinical prospects of herbal natural products.

Pathomechanisms of Diabetic Kidney Disease

The worldwide occurrence of diabetic kidney disease (DKD) is swiftly rising, primarily attributed to the growing population of individuals affected by type 2 diabetes. This surge has been transformed into a substantial global concern, placing additional strain on healthcare systems already grappling with significant demands. The pathogenesis of DKD is intricate, originating with hyperglycemia, which triggers various mechanisms and pathways: metabolic, hemodynamic, inflammatory, and fibrotic which ultimately lead to renal damage. Within each pathway, several mediators contribute to the development of renal structural and functional changes. Some of these mediators, such as inflammatory cytokines, reactive oxygen species, and transforming growth factor β are shared among the different pathways, leading to significant overlap and interaction between them. While current treatment options for DKD have shown advancement over previous strategies, their effectiveness remains somewhat constrained as patients still experience residual risk of disease progression. Therefore, a comprehensive grasp of the molecular mechanisms underlying the onset and progression of DKD is imperative for the continued creation of novel and groundbreaking therapies for this condition. In this review, we discuss the current achievements in fundamental research, with a particular emphasis on individual factors and recent developments in DKD treatment.

Promising therapeutic mechanism for Chinese herbal medicine in ameliorating renal fibrosis in diabetic nephropathy

Diabetic nephropathy (DN) is one of the most serious chronic microvascular abnormalities of diabetes mellitus and the major cause of uremia. Accumulating evidence has confirmed that fibrosis is a significant pathological feature that contributes to the development of chronic kidney disease in DN. However, the exact mechanism of renal fibrosis in DN is still unclear, which greatly hinders the treatment of DN. Chinese herbal medicine (CHM) has shown efficacy and safety in ameliorating inflammation and albuminuria in diabetic patients. In this review, we outline the underlying mechanisms of renal fibrosis in DN, including oxidative stress (OS) generation and OS-elicited ASK1-p38/JNK activation. Also, we briefly summarize the current status of CHM treating DN by improving renal fibrosis. The treatment of DN by inhibiting ASK1 activation to alleviate renal fibrosis in DN with CHM will promote the discovery of novel therapeutic targets for DN and provide a beneficial therapeutic method for DN.

Bioinformatics identification of ferroptosis-related genes and therapeutic drugs in rheumatoid arthritis

Introduction

Rheumatoid arthritis (RA) is a chronic immune disease characterized by synovial inflammation and bone destruction, with a largely unclear etiology. Evidence has indicated that ferroptosis may play an increasingly important role in the onset and development of RA. However, ferroptosis-related genes are still largely unexplored in RA. Therefore, this work focused on identifying and validating the potential ferroptosis-related genes involved in RA through bioinformatics analysis.

Methods

We screened differentially expressed ferroptosis-related genes (DEFGs) between RA patients and healthy individuals based on GSE55235 dataset. Subsequently, correlation analysis, protein-protein interaction (PPI) network analysis, GO, and KEGG enrichment analyses were performed using these DEFGs. Finally, our results were validated by GSE12021 dataset.

Results

We discovered 34 potential DEFGs in RA based on bioinformatics analysis. According to functional enrichment analysis, these genes were mainly enriched in HIF-1 signaling pathway, FoxO signaling pathway, and Ferroptosis pathway. Four genes (GABARPL1, DUSP1, JUN, and MAPK8) were validated to be downregulated by GSE12021 dataset and were diagnostic biomarkers and therapeutic targets for RA via the regulation of ferroptosis.

Discussion

Our results help shed more light on the pathogenesis of RA. Ferroptosis-related genes in RA are valuable diagnostic biomarkers and they will be exploited clinically as therapeutic targets in the future.

Echinochrome A Prevents Diabetic Nephropathy by Inhibiting the PKC-Iota Pathway and Enhancing Renal Mitochondrial Function in db/db Mice

Echinochrome A (EchA) is a natural bioproduct extracted from sea urchins, and is an active component of the clinical drug, Histochrome®. EchA has antioxidant, anti-inflammatory, and antimicrobial effects. However, its effects on diabetic nephropathy (DN) remain poorly understood. In the present study, seven-week-old diabetic and obese db/db mice were injected with Histochrome (0.3 mL/kg/day; EchA equivalent of 3 mg/kg/day) intraperitoneally for 12 weeks, while db/db control mice and wild-type (WT) mice received an equal amount of sterile 0.9% saline. EchA improved glucose tolerance and reduced blood urea nitrogen (BUN) and serum creatinine levels but did not affect body weight. In addition, EchA decreased renal malondialdehyde (MDA) and lipid hydroperoxide levels, and increased ATP production. Histologically, EchA treatment ameliorated renal fibrosis. Mechanistically, EchA suppressed oxidative stress and fibrosis by inhibiting protein kinase C-iota (PKCι)/p38 mitogen-activated protein kinase (MAPK), downregulating p53 and c-Jun phosphorylation, attenuating NADPH oxidase 4 (NOX4), and transforming growth factor-beta 1 (TGFβ1) signaling. Moreover, EchA enhanced AMPK phosphorylation and nuclear factor erythroid-2-related factor 2 (NRF2)/heme oxygenase 1 (HO-1) signaling, improving mitochondrial function and antioxidant activity. Collectively, these findings demonstrate that EchA prevents DN by inhibiting PKCι/p38 MAPK and upregulating the AMPKα/NRF2/HO-1 signaling pathways in db/db mice, and may provide a therapeutic option for DN.

A patent review of MAPK inhibitors (2018 - present)

INTRODUCTION

The mitogen-activated protein kinase (MAPK) family consist of p38 MAP kinases, c-Jun N-terminal kinases (JNKs) and extracellular signal-regulated kinases (ERKs). They are involved in a multitude of diseases, including inflammatory, autoimmune, neurodegenerative, and metabolic diseases as well as cancer. In recent years, further developments in the field of MAPK-inhibitors have been reported, including an isoform or downstream target selective inhibition of MAPKs as well as target protein degradation approaches.

AREAS COVERED

This review summarizes newly patented MAPK-inhibitors that were claimed between 2018 and early 2023. Presented are the patents as well as their corresponding publications, the storyline of development, and clinical trials involving these compounds. This article elaborates a total of 27 patents, which were identified using established search engines.

EXPERT OPINION

Although industrial research on MAPK-inhibitors has been ongoing for more than 20 years, novel clinical trials of MAPK-inhibitors as potential drug candidates are still being conducted in the period under review. Recently reported inhibitors show an excellent selectivity profile and are even achieving selectivity between closely related isoforms. This progression offers the possibility to eliminate unwanted side effects and may finally lead to the approval of the first MAPK-inhibitor.

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.

Targeted inhibition of ZAK ameliorates renal interstitial fibrosis

ZAK (sterile alpha motif and leucine zipper-containing kinase) is a newly discovered member of the subfamily of mitogen-activated protein kinase kinase kinases (MAP3Ks). The role of ZAK in kidney disease remains largely unknown. In this study, we systematically investigated the expression and function of ZAK in the progression of tubulointerstitial fibrosis (TIF). ZAK was induced, predominantly in tubular epithelium, in both fibrotic kidneys of human and mouse models with TIF. ZAK expression level was correlated with the extent of renal fibrosis and the decline of eGFR of CKD patients. Depleting ZAK attenuated TIF and inflammation induced by unilateral ureteral occlusion (UUO) together with decreased activation of p38 MAPK and Smads signaling. Moreover, we demonstrated that overexpressed ZAK was in complex with Smad2/3 and TGF-β receptor Ⅰ (TβRI). Whereas, silencing endogenous ZAK ameliorated the amount of Smad2/3 recruited to TβRI. Moreover, we discovered a novel small molecule inhibitor of ZAK, named 6p. In vitro, incubation with 6p inhibited TGF-β1-induced fibrogenic response in NRK52E cells. In vivo, intragastric administration of 6p ameliorated TIF and inflammation in UUO and unilateral ischemia-reperfusion injury model. Delayed administration of 6p was also effective in retarding the progression of the established TIF. In conclusion, ZAK is a novel therapeutic target for TIF, and 6p might be a potential therapeutic agent for TIF.

The Systemic Effects of Exercise on the Systemic Effects of Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive degenerative disorder and a leading cause of dementia in the elderly. The etiology of AD is multifactorial, including an increased oxidative state, deposition of amyloid plaques, and neurofibrillary tangles of the tau protein. The formation of amyloid plaques is considered one of the first signs of the illness, but only in the central nervous system (CNS). Interestingly, results indicate that AD is not just localized in the brain but is also found in organs distant from the brain, such as the cardiovascular system, gut microbiome, liver, testes, and kidney. These observations make AD a complex systemic disorder. Still, no effective medications have been found, but regular physical activity has been considered to have a positive impact on this challenging disease. While several articles have been published on the benefits of physical activity on AD development in the CNS, its peripheral effects have not been discussed in detail. The provocative question arising is the following: is it possible that the beneficial effects of regular exercise on AD are due to the systemic impact of training, rather than just the effects of exercise on the brain? If so, does this mean that the level of fitness of these peripheral organs can directly or indirectly influence the incidence or progress of AD? Therefore, the present paper aims to summarize the systemic effects of both regular exercise and AD and point out how common exercise-induced adaptation via peripheral organs can decrease the incidence of AD or attenuate the progress of AD.

Fatty acid-binding protein 4 is a therapeutic target for septic acute kidney injury by regulating inflammatory response and cell apoptosis

Sepsis is a systemic inflammatory state in response to infection, and concomitant acute kidney injury (AKI) significantly increases morbidity and mortality. Growing evidence suggests that fatty acid-binding protein 4 (FABP4) is critically involved in kidney diseases, while its role in septic AKI remains unknown. Here, FABP4 was mainly upregulated in renal tubular epithelial cells (RTECs) following cecal ligation and puncture (CLP)- or lipopolysaccharide (LPS)-induced septic AKI. FABP4 inhibition by genetic deletion or BMS309403 treatment both attenuated kidney dysfunction and pathological injury in CLP- or LPS-treated mice. Notably, RTEC-specific deletion of FABP4 also showed similar renoprotective effects. Moreover, FABP4 inhibition alleviated inflammation and apoptosis in CLP-injured kidneys and LPS-stimulated mouse tubular epithelial cells. Mechanistically, TLR4 blockage improved sepsis-induced kidney injury, as well as suppressed c-Jun phosphorylation and FABP4 expression, where c-Jun knockdown also inhibited LPS-stimulated FABP4 level. Meanwhile, FABP4 inhibition reduced the elevated phosphorylated c-Jun, while the levels of TLR4 and MyD88 were uninfluenced. Collectively, the increased FABP4 in RTECs is dependent on TLR4/c-Jun signaling activation and contributes to kidney injury, by forming a positive feedback loop with c-Jun to aggravate inflammation and apoptosis in septic AKI. Thus, FABP4 may be a therapeutic target for septic AKI.

Macrophages in the kidney in health, injury and repair

Macrophages are a key component of the renal mononuclear phagocyte system, playing a major role in defense against infection, renal injury and repair. Yolk sac macrophage precursors seed the early embryonic kidney and are important for renal development. Later, renal macrophages are derived from hematopoietic stem cells and in adult life, there is a significant contribution from circulating monocytes, which is enhanced in response to infection or injury. Macrophages are highly plastic and can alter their phenotype in response to cues from parenchymal renal cells. Danger-associated molecules released from injured kidney cells may activate macrophages toward a pro-inflammatory phenotype, mediating further recruitment of inflammatory cells, exacerbating renal injury and activating renal fibroblasts to promote scarring. In acute kidney injury, once the injury stimulus has abated, macrophages may adopt a more reparative phenotype, dampening the immune response and promoting repair of renal tissue. However, in chronic kidney disease ongoing activation of pro-inflammatory monocytes and persistence of reparative macrophages leads to glomerulosclerosis and tubulointerstitial fibrosis, the hallmarks of end-stage kidney disease. Several strategies to inhibit the recruitment, activation and secretory products of pro-inflammatory macrophages have proven beneficial in pre-clinical models and are now undergoing clinical trials in patients with kidney disease. In addition, macrophages may be utilized in cell therapy as a "Trojan Horse" to deliver targeted therapies to the kidney. Single-cell RNA sequencing has identified a previously unappreciated spectrum of macrophage phenotypes, which may be selectively present in injury or repair, and ongoing functional analyses of these subsets may identify more specific targets for therapeutic intervention.

SARS-CoV-2 infects the human kidney and drives fibrosis in kidney organoids

Kidney failure is frequently observed during and after COVID-19, but it remains elusive whether this is a direct effect of the virus. Here, we report that SARS-CoV-2 directly infects kidney cells and is associated with increased tubule-interstitial kidney fibrosis in patient autopsy samples. To study direct effects of the virus on the kidney independent of systemic effects of COVID-19, we infected human-induced pluripotent stem-cell-derived kidney organoids with SARS-CoV-2. Single-cell RNA sequencing indicated injury and dedifferentiation of infected cells with activation of profibrotic signaling pathways. Importantly, SARS-CoV-2 infection also led to increased collagen 1 protein expression in organoids. A SARS-CoV-2 protease inhibitor was able to ameliorate the infection of kidney cells by SARS-CoV-2. Our results suggest that SARS-CoV-2 can directly infect kidney cells and induce cell injury with subsequent fibrosis. These data could explain both acute kidney injury in COVID-19 patients and the development of chronic kidney disease in long COVID.

Dual-Specificity Phosphatases and Kidney Diseases

BACKGROUND

Dual-specificity phosphatases (DUSPs) belong to the family of protein tyrosine phosphatases, which can dephosphorylate both serine/threonine and tyrosine residues. During the past decades, DUSPs have been implicated in various physiological and pathological activities. Besides mitogen-activated protein kinases (MAPKs) as the main substrates, other protein and nonprotein substrates can also be dephosphorylated by DUSPs. Aberrant regulations of DUSPs have been found in various diseases such as cancer, neurological disorders, and kidney diseases, suggesting the involvement of DUSPs in the pathogenesis of diseases.

SUMMARY

In this review, we summarize the general characteristics of DUSPs and the research progress made in the field of kidney diseases, including diabetic nephropathy, hypertensive nephropathy, chronic kidney disease, acute kidney injury, and lupus nephritis. As the main biochemical function of DUSPs is to dephosphorylate MAPKs activity, decreased DUSPs are found in kidney disease models, whereas forced DUSPs expression reverses the disease presentation, which was proved by using transgenic or gene knockout model.

KEY MESSAGES

Mounting evidence demonstrates that DUSPs have essential physiological and pathological functions in kidney disease. Fully understanding the functions and mechanisms of DUSPs in kidney disease contributes to their clinical application in translation medicine.

c-Jun N-terminal kinase (JNK) signaling contributes to cystic burden in polycystic kidney disease

Polycystic kidney disease is an inherited degenerative disease in which the uriniferous tubules are replaced by expanding fluid-filled cysts that ultimately destroy organ function. Autosomal dominant polycystic kidney disease (ADPKD) is the most common form, afflicting approximately 1 in 1,000 people. It primarily is caused by mutations in the transmembrane proteins polycystin-1 (Pkd1) and polycystin-2 (Pkd2). The most proximal effects of Pkd mutations leading to cyst formation are not known, but pro-proliferative signaling must be involved for the tubule epithelial cells to increase in number over time. The c-Jun N-terminal kinase (JNK) pathway promotes proliferation and is activated in acute and chronic kidney diseases. Using a mouse model of cystic kidney disease caused by Pkd2 loss, we observe JNK activation in cystic kidneys and observe increased nuclear phospho c-Jun in cystic epithelium. Genetic removal of Jnk1 and Jnk2 suppresses the nuclear accumulation of phospho c-Jun, reduces proliferation and reduces the severity of cystic disease. While Jnk1 and Jnk2 are thought to have largely overlapping functions, we find that Jnk1 loss is nearly as effective as the double loss of Jnk1 and Jnk2. Jnk pathway inhibitors are in development for neurodegeneration, cancer, and fibrotic diseases. Our work suggests that the JNK pathway should be explored as a therapeutic target for ADPKD.

Autosomal dominant polycystic kidney disease is a leading cause of end stage renal disease requiring dialysis or kidney transplant. During disease development, the cells lining the kidney tubules proliferate. This proliferation transforms normally small diameter tubules into fluid-filled cysts that enlarge with time, eventually destroying all kidney function. Despite decades of research, polycystic kidney disease remains incurable. Furthermore, the precise signaling events involved in cyst initiation and growth remain unclear. The c-Jun N-terminal kinase (JNK), is a major pathway regulating cellular proliferation and differentiation but its importance to polycystic kidney disease was not known. We show that JNK activity is elevated in cystic kidneys and that reducing JNK activity decreases cyst growth pointing to JNK inhibition as a therapeutic strategy for treating polycystic kidney disease.

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

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

Klotho overexpression protects against renal aging along with suppression of transforming growth factor-β1 signaling pathways

Klotho is an antiaging protein reported to suppress transforming growth factor-β1 (TGF-β1) signaling. Aging kidneys are characterized by interstitial fibrosis, accumulation of cell cycle-arrested cells, and increased levels of oxidative stress. TGF-β1 signaling is involved in these processes. In this study, we investigated whether klotho overexpression improves these features in the kidneys of aging mice and examined the inhibitory effect of klotho on signaling molecules related to transforming growth of TGF-β1. Klotho transgenic (KLTG) and wild-type (WT) mice were used, and 8-wk-old and 24-mo-old mice were defined as young and aging, respectively. We found that klotho expression was decreased in aging WT mice, but it was maintained in aging KLTG mice. Klotho overexpression improved the survival of 24-mo-old mice. Although the serum Ca²⁺ level was significantly lower in aging KLTG mice than in aging WT mice, the serum phosphate level did not differ between these mice. Klotho overexpression attenuated the increases in blood pressure, serum blood urea nitrogen level, and serum creatinine level in aging mice. Interstitial fibrosis, accumulation of cell cycle-arrested cells, and oxidative stress did not differ between young KLTG and WT mice, but they were significantly suppressed in aging KLTG mice compared with aging WT mice. Furthermore, the expression of TGF-β1-related signaling molecules was increased in aging WT mice, whereas it was inhibited in aging KLTG mice. These data suggest that klotho overexpression protects against kidney aging along with suppression of TGF-β1 signaling pathways.NEW & NOTEWORTHY Klotho is considered as an antiaging protein, and its overexpression may be a candidate therapy for protection against kidney damage with advanced aging. Although multiple factors are involved in the aging process, we showed that klotho overexpression inhibited interstitial fibrosis, accumulation of cell cycle-arrested cells, and increased levels of oxidative stress in the kidneys of aging mice, suppressing transforming growth factor-β1-related signaling pathways. The present data showed that klotho overexpression protects against age-associated kidney damage.

SB203580-A Potent p38 MAPK Inhibitor Reduces the Profibrotic Bronchial Fibroblasts Transition Associated with Asthma

Subepithelial fibrosis is a component of the remodeling observed in the bronchial wall of patients diagnosed with asthma. In this process, human bronchial fibroblasts (HBFs) drive the fibroblast-to-myofibroblast transition (FMT) in response to transforming growth factor-β₁ (TGF-β₁), which activates the canonical Smad-dependent signaling. However, the pleiotropic properties of TGF-β₁ also promote the activation of non-canonical signaling pathways which can affect the FMT. In this study we investigated the effect of p38 mitogen-activated protein kinase (MAPK) inhibition by SB203580 on the FMT potential of HBFs derived from asthmatic patients using immunocytofluorescence, real-time PCR and Western blotting methods. Our results demonstrate for the first time the strong effect of p38 MAPK inhibition on the TGF-β₁-induced FMT potential throughout the strong attenuation of myofibroblast-related markers: α-smooth muscle actin (α-SMA), collagen I, fibronectin and connexin 43 in HBFs. We suggest the pleiotropic mechanism of SB203580 on FMT impairment in HBF populations by the diminishing of TGF-β/Smad signaling activation and disturbances in the actin cytoskeleton architecture along with the maturation of focal adhesion sites. These observations justify future research on the role of p38 kinase in FMT efficiency and bronchial wall remodeling in asthma.

Redox signaling pathways in unilateral ureteral obstruction (UUO)-induced renal fibrosis

Unilateral ureteral obstruction (UUO) is an experimental rodent model that mimics renal fibrosis associated with obstructive nephropathy in an accelerated manner. After UUO, the activation of the renin-angiotensin system (RAS), nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) and mitochondrial dysfunction lead to reactive oxygen species (ROS) overproduction in the kidney. ROS are secondary messengers able to induce post-translational modifications (PTMs) in redox-sensitive proteins, which activate or deactivate signaling pathways. Therefore, in UUO, it has been proposed that ROS overproduction causes changes in said pathways promoting inflammation, oxidative stress, and apoptosis that contribute to fibrosis development. Furthermore, mitochondrial metabolism impairment has been associated with UUO, contributing to renal damage in this model. Although ROS production and oxidative stress have been studied in UUO, the development of renal fibrosis associated with redox signaling pathways has not been addressed. This review focuses on the current information about the activation and deactivation of signaling pathways sensitive to a redox state and their effect on mitochondrial metabolism in the fibrosis development in the UUO model.

TGFβ1 protein trap AVID200 beneficially affects hematopoiesis and bone marrow fibrosis in myelofibrosis

Myelofibrosis (MF) is a progressive chronic myeloproliferative neoplasm characterized by hyperactivation of JAK/STAT signaling and dysregulation of the transcription factor GATA1 in megakaryocytes (MKs). TGF-β plays a pivotal role in the pathobiology of MF by promoting BM fibrosis and collagen deposition and by enhancing the dormancy of normal hematopoietic stem cells (HSCs). In this study, we show that MF-MKs elaborated significantly greater levels of TGF-β1 than TGF-β2 and TGF-β3 to a varying degree, and we evaluated the ability of AVID200, a potent TGF-β1/TGF-β3 protein trap, to block the excessive TGF-β signaling. Treatment of human mesenchymal stromal cells with AVID200 significantly reduced their proliferation, decreased phosphorylation of SMAD2, and interfered with the ability of TGF-β1 to induce collagen expression. Moreover, treatment of MF mononuclear cells with AVID200 led to increased numbers of progenitor cells (PCs) with WT JAK2 rather than mutated JAK2V617F. This effect of AVID200 on MF PCs was attributed to its ability to block TGF-β1–induced p57^Kip2 expression and SMAD2 activation, thereby allowing normal rather than MF PCs to preferentially proliferate and form hematopoietic colonies. To assess the in vivo effects of AVID200, Gata1^lo mice, a murine model of MF, were treated with AVID200, resulting in the reduction in BM fibrosis and an increase in BM cellularity. AVID200 treatment also increased the frequency and numbers of murine progenitor cells as well as short-term and long-term HSCs. Collectively, these data provide the rationale for TGF-β1 blockade, with AVID200 as a therapeutic strategy for patients with MF.

Signaling Pathways Involved in Diabetic Renal Fibrosis

Diabetic kidney disease (DKD), as the most common complication of diabetes mellitus (DM), is the major cause of end-stage renal disease (ESRD). Renal interstitial fibrosis is a crucial metabolic change in the late stage of DKD, which is always considered to be complex and irreversible. In this review, we discuss the pathological mechanisms of diabetic renal fibrosis and discussed some signaling pathways that are closely related to it, such as the TGF-β, MAPK, Wnt/β-catenin, PI3K/Akt, JAK/STAT, and Notch pathways. The cross-talks among these pathways were then discussed to elucidate the complicated cascade behind the tubulointerstitial fibrosis. Finally, we summarized the new drugs with potential therapeutic effects on renal fibrosis and listed related clinical trials. The purpose of this review is to elucidate the mechanisms and related pathways of renal fibrosis in DKD and to provide novel therapeutic intervention insights for clinical research to delay the progression of renal fibrosis.

Purine adducts as a presumable missing link for aristolochic acid nephropathy-related cellular energy crisis, potential anti-fibrotic prevention and treatment

Aristolochic acid nephropathy is a progressive exposome-induced disease characterized by tubular atrophy and fibrosis culminating in end-stage renal disease and malignancies. The molecular mechanisms of the energy crisis as a putative cause of fibrosis have not yet been elucidated. In light of the fact that aristolochic acid forms DNA and RNA adducts by covalent binding of aristolochic acid metabolites to exocyclic amino groups of (deoxy)adenosine and (deoxy)guanosine, we hypothesize here that similar aristolochic acid adducts may exist with other purine-containing molecules. We also provide new insights into the aristolochic acid-induced energy crisis and presumably a link between already known mechanisms. In addition, an overview of potential targets in fibrosis treatment is provided, which is followed by recommendations on possible preventive measures that could be taken to at least postpone or partially alleviate aristolochic acid nephropathy.

Physical Training Inhibits the Fibrosis Formation in Alzheimer's Disease Kidney Influencing the TGFβ Signaling Pathways

Background:

Alzheimer’s disease (AD) is a neurodegenerative illness, with several peripheral pathological signs such as accumulation of amyloid-β (Aβ) plaques in the kidney. Alterations of transforming growth factor β (TGFβ) signaling in the kidney can induce fibrosis, thus disturbing the elimination of Aβ.

Objective:

A protective role of increased physical activity has been proven in AD and in kidney fibrosis, but it is not clear whether TGFβ signalization is involved in this effect.

Methods:

The effects of long-term training on fibrosis were investigated in the kidneys of mice representing a model of AD (B6C3-Tg(APPswe,PSEN1dE9)85Dbo/J) by comparing wild type and AD organs. Alterations of canonical and non-canonical TGFβ signaling pathways were followed with PCR, western blot, and immunohistochemistry.

Results:

Accumulation of collagen type I and interstitial fibrosis were reduced in kidneys of AD mice after long-term training. AD induced the activation of canonical and non-canonical TGFβ pathways in non-trained mice, while expression levels of signal molecules of both TGFβ pathways became normalized in trained AD mice. Decreased amounts of phosphoproteins with molecular weight corresponding to that of tau and the cleaved C-terminal of AβPP were detected upon exercising, along with a significant increase of PP2A catalytic subunit expression.

Conclusion:

Our data suggest that physical training has beneficial effects on fibrosis formation in kidneys of AD mice and TGFβ signaling plays a role in this phenomenon.

Multi-target pharmacological mechanisms of Salvia miltiorrhiza against oral submucous fibrosis: A network pharmacology approach

OBJECTIVES

The herb Salvia miltiorrhiza is used to treat oral submucous fibrosis (OSF); however, the mechanism underlying its efficacy has not been elucidated. As such, a network pharmacology-based approach was applied to investigate the potential mechanisms of Salvia miltiorrhiza against OSF.

MATERIALS AND METHODS

Potential targets of Salvia miltiorrhiza were collected by Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform, Bioinformatics Analysis Tool for Molecular Mechanism of Traditional Chinese Medicine, and Swiss Target Prediction. Potential targets of OSF were collected from DisGeNET, GeneCards, and National Center for Biotechnology Information Gene database. Salvia miltiorrhiza against OSF targets protein-protein interaction and enrichment analyses network were constructed by Cytoscape and Metascape.

RESULTS

Twelve active ingredients from Salvia miltiorrhiza and 57 potential OSF-related targets were identified. The constructed network predicted seven potential key targets of Salvia miltiorrhiza for the treatment of OSF. Functional enrichment analysis showed that biological processes such as cellular response to drugs and pathways such as bladder cancer were mainly regulated by the Salvia miltiorrhiza active ingredient targets. Furthermore, the protein-protein interaction network demonstrated that the molecular complex detection components were mainly related to the ErbB signaling pathway, cancer pathways and IL-17 signaling.

CONCLUSIONS

A network approach was employed to document how Salvia miltiorrhiza active ingredients change various pathways against OSF. Salvia miltiorrhiza active ingredient targets against OSF involved CYP19A1, EGFR, PTPN11, ACHE, TERT, MAPK8 and PGR and were enriched in several signaling pathways.

Indazole as a Privileged Scaffold: The Derivatives and their Therapeutic Applications

BACKGROUND

Heterocyclic compounds, also called heterocycles, are a major class of organic chemical compound that plays a vital role in the metabolism of all living cells. The heterocyclic compound, indazole, has attracted more attention in recent years and is widely present in numerous commercially available drugs. Indazole-containing derivatives, representing one of the most important heterocycles in drug molecules, are endowed with a broad range of biological properties.

METHODS

A literature search was conducted in PubMed, Google Scholar and Web of Science regarding articles related to indazole and its therapeutic application.

RESULTS

The mechanism and structure-activity relationship of indazole and its derivatives were described. Based on their versatile biological activities, the compounds were divided into six groups: anti-inflammatory, antibacterial, anti-HIV, antiarrhythmic, antifungal and antitumour. At least 43 indazole-based therapeutic agents were found to be used in clinical application or clinical trials.

CONCLUSION

This review is a guide for pharmacologists who are in search of valid preclinical/clinical drug compounds where the progress of approved marketed drugs containing indazole scaffold is examined from 1966 to the present day. Future direction involves more diverse bioactive moieties with indazole scaffold and greater insights into its mechanism.

JNK signaling pathway in metabolic disorders: An emerging therapeutic target

Metabolic Syndrome is a multifactorial disease associated with increased risk of cardiovascular disorders, type 2 diabetes mellitus, fatty liver disease, etc. Various stress stimuli such as reactive oxygen species, endoplasmic reticulum stress, mitochondrial dysfunction, increased cytokines, or free fatty acids are known to aggravate progressive development of hyperglycemia and hyperlipidemia. Although the exact mechanism contributing to altered metabolism is unclear. Evidence suggests stress kinase role to be a crucial one in metabolic syndrome. Stress kinase, c-jun N-terminal kinase activation (JNK) is involved in various metabolic manifestations including obesity, insulin resistance, fatty liver disease as well as cardiometabolic disorders. It emerged as a foremost mediator in regulating metabolism in the liver, skeletal muscle, adipose tissue as well as pancreatic β cells. It has three isoforms each having a unique and tissue-specific role in altered metabolism. Current findings based on genetic manipulation or chemical inhibition studies identified JNK isoforms to play a central role in the regulation of whole-body metabolism, suggesting it to be a novel therapeutic target. Hence, it is imperative to elucidate its role in metabolic syndrome onset and progression. The purpose of this review is to elucidate in vitro and in vivo implications of JNK signaling along with the therapeutic strategy to inhibit specific isoform. Since metabolic syndrome is an array of diseases and complex pathway, carefully examining each tissue will be important for specific treatment strategies.

JNK signaling as a target for anticancer therapy

The JNKs are members of mitogen-activated protein kinases (MAPK) which regulate many physiological processes including inflammatory responses, macrophages, cell proliferation, differentiation, survival, and death. It is increasingly clear that the continuous activation of JNKs has a role in cancer development and progression. Therefore, JNKs represent attractive oncogenic targets for cancer therapy using small molecule kinase inhibitors. Studies showed that the two major JNK proteins JNK1 and JNK2 have opposite functions in different types of cancers, which need more specification in the design of JNK inhibitors. Some of ATP- competitive and ATP non-competitive inhibitors have been developed and widely used in vitro, but this type of inhibitors lack selectivity and inhibits phosphorylation of all JNK substrates and may lead to cellular toxicity. In this review, we summarized and discussed the strategies of JNK binding inhibitors and the role of JNK signaling in the pathogenesis of different solid and hematological malignancies.

JUN Amino-Terminal Kinase 1 Signaling in the Proximal Tubule Causes Cell Death and Acute Renal Failure in Rat and Mouse Models of Renal Ischemia/Reperfusion Injury

Activation of the JUN amino-terminal kinase (JNK) pathway is prominent in most forms of acute and progressive tubulointerstitial damage, including acute renal ischemia/reperfusion injury (IRI). Two forms of JNK, JNK1 and JNK2, are expressed in the kidney. Systemic administration of pan-JNK inhibitors suppresses renal IRI; however, the contribution of JNK1 versus JNK2, and the specific role of JNK activation in the proximal tubule in IRI, remains unknown. These questions were addressed in rat and mouse models of acute bilateral renal IRI. Administration of the JNK inhibitor, CC-930, substantially reduced the severity of renal failure, tubular damage, and inflammation at 24 hours in a rat IRI model. Additionally, Jnk1^-/- mice, but not Jnk2^-/- mice, were shown to be significantly protected against acute renal failure, tubular damage, and inflammation in the IRI model. Furthermore, mice with conditional Jnk1 deletion in the proximal tubule also showed considerable protection from IRI-induced renal failure, tubular damage, and inflammation. Finally, primary cultures of Jnk1^-/-, but not Jnk2^-/-, tubular epithelial cells were protected from oxidant-induced cell death, in association with preventing phosphorylation of proteins (receptor interacting serine/threonine kinase 3 and mixed lineage kinase domain-like pseudokinase) in the necroptosis pathway. In conclusion, JNK1, but not JNK2, plays a specific role in IRI-induced cell death in the proximal tubule, leading to acute renal failure.

c-Jun Amino Terminal Kinase Signaling Promotes Aristolochic Acid-Induced Acute Kidney Injury

Aristolochic acid (AA) is a toxin that induces DNA damage in tubular epithelial cells of the kidney and is the cause of Balkan Nephropathy and Chinese Herb Nephropathy. In cultured tubular epithelial cells, AA induces a pro-fibrotic response via the c-Jun amino terminal kinase (JNK) signaling pathway. This study investigated the in vivo role of JNK signaling with a JNK inhibitor (CC-930) in mouse models of acute high dose AA-induced kidney injury (day 3) and renal fibrosis induced by chronic low dose AA exposure (day 22). CC-930 treatment inhibited JNK signaling and protected from acute AA-induced renal function impairment and severe tubular cell damage on day 3, with reduced macrophage infiltration and expression of pro-inflammatory molecules. In the chronic model, CC-930 treatment inhibited JNK signaling but did not affect AA-induced renal function impairment, tubular cell damage including the DNA damage response and induction of senescence, or renal fibrosis; despite a reduction in the macrophage pro-inflammatory response. In conclusion, JNK signaling contributes to acute high dose AA-induced tubular cell damage, presumably via an oxidative stress-dependent mechanism, but is not involved in tubular atrophy and senescence that promote chronic kidney disease caused by ongoing DNA damage in chronic low dose AA exposure.

Cyclophilin Inhibition Protects Against Experimental Acute Kidney Injury and Renal Interstitial Fibrosis

Cyclophilins have important homeostatic roles, but following tissue injury, cyclophilin A (CypA) can promote leukocyte recruitment and inflammation, while CypD can facilitate mitochondrial-dependent cell death. This study investigated the therapeutic potential of a selective cyclophilin inhibitor (GS-642362), which does not block calcineurin function, in mouse models of tubular cell necrosis and renal fibrosis. Mice underwent bilateral renal ischemia/reperfusion injury (IRI) and were killed 24 h later: treatment with 10 or 30 mg/kg/BID GS-642362 (or vehicle) began 1 h before surgery. In the second model, mice underwent unilateral ureteric obstruction (UUO) surgery and were killed 7 days later; treatment with 10 or 30 mg/kg/BID GS-642362 (or vehicle) began 1 h before surgery. GS-642362 treatment gave a profound and dose-dependent protection from acute renal failure in the IRI model. This protection was associated with reduced tubular cell death, including a dramatic reduction in neutrophil infiltration. In the UUO model, GS-642362 treatment significantly reduced tubular cell death, macrophage infiltration, and renal fibrosis. This protective effect was independent of the upregulation of IL-2 and activation of the stress-activated protein kinases (p38 and JNK). In conclusion, GS-642362 was effective in suppressing both acute kidney injury and renal fibrosis. These findings support further investigation of cyclophilin blockade in other types of acute and chronic kidney disease.

Up-regulation of PKR pathway contributes to L-NAME induced hypertension and renal damage

Objective

Hypertension induced kidney damage is often associated with fibrosis and tubular apoptosis. Double-stranded protein kinase (PKR) is a well recognized inducer of inflammation and apoptosis. However, role of PKR in hypertension coupled renal damage is still not explored. Therefore here we sought to investigate the role of PKR in the pathogenesis of L-NAME induced hypertension and renal damage in Wistar rats and the underneath molecular mechanism.

Methods

L-NAME (40 mg/kg, p.o) and imoxin (0.5 mg/kg, i.p) was given to Wistar rats for 4 weeks. Increased eNOS expression, serum creatinine, BUN and changes in mean arterial pressure confirmed for hypertensive renal damage. Western blot and immunohistochemistry was carried out for PKR and markers for fibrosis and apoptosis. Morphological alterations were assessed by H&E staining. Sirius red and Masson's Trichrome staining was performed for collagen and fibrosis. TUNEL assay was done for tubular cell death and apoptosis.

Results

Increased expression of PKR and its downstream markers were reported in L-NAME rats, attenuation was observed with imoxin treatment. L-NAME treated rats showed a significant increase in MAP, serum calcium, creatinine and BUN along with the significant morphological changes, attenuation was reported with the imoxin treatment.

Conclusion

PKR is a core contributor in the pathogenesis of L-NAME induced renal damage and tubular apoptosis. Therapeutically targeting of PKR could be an attractive approach to treat the renal complications associated with hypertension.

Transforming Growth Factor β1 Induces Epithelial–mesenchymal Transition by Activating the Jnk–SMAD3 Pathway in Rat Peritoneal Mesothelial Cells

⋄ Background

Peritoneal fibrosis is a serious complication in long-term peritoneal dialysis (PD) patients. Epithelial-mesenchymal transition (EMT) plays an important role in peritoneal fibrosis, and TGFβ1 is the crucial inducer of EMT. Phosphorylation of Smad proteins is required for TGFβ1-induced EMT. It was reported that C-Jun N-terminal kinase (JNK) was involved in the TGFβ1/Smad signaling pathway and might regulate the activation of Smad proteins. However, whether JNK is activated by TGFβ1 in rat peritoneal mesothelial cells (RPMCs) and the role taken by JNK signaling in EMT induced by TGFβ1 remains undetermined. In the present study, we investigated the role of JNK-Smad pathway in EMT induced by TGFβ1 in RPMCs.

⋄ Methods

We harvested RPMCs from the peritoneum of male Sprague-Dawley rats and then cultured the cells in Dulbecco modified Eagle medium / F12 medium with 15% (volume:volume) fetal bovine serum. The cells were pretreated with SP600125, a specific inhibitor of JNK, for 4 hours before incubation with TGFβ1. The protein expression levels of phosphorylated JNK, Smad2, and Smad3 were detected by Western blotting. The messenger RNA levels and protein expression of α-smooth muscle actin (α-SMA), E-cadherin, and collagen I were determined with reverse transcriptase polymerase chain reaction and Western blotting respectively.

⋄ Results

Expression of α-SMA and collagen I were significantly increased and expression of E-cadherin decreased with TGFβ1 in RPMCs. Transforming growth factor β1 can stimulate phosphorylated JNK expression from 5 minutes, with the peak at 10 minutes, and phosphorylated Smad2 and Smad3 expression from 10 minutes, with the peak at 30 minutes. The addition of SP600125, which blocked activation of JNK, effectively inhibited TGFβ1-induced phosphorylation of Smad3, but not Smad2. Also, our results showed that SP600125 effectively suppressed TGFβ1-induced high expression of α-SMA and collagen I, and prevented TGFβ1-induced downregulation of E-cadherin expression in RPMCs.

⋄ Conclusions

This study demonstrated that JNK signaling may play an important role in EMT induced by TGFβ1 in RPMCs through activation of Smad3, suggesting that JNK inhibitor may prove to be a novel therapeutic agent for peritoneal fibrosis.

Apigenin Alleviates Renal Fibroblast Activation through AMPK and ERK Signaling Pathways In Vitro

OBJECTIVE

Renal fibrosis is a common pathway leading to the progression of chronic kidney disease. Activated fibroblasts contribute remarkably to the development of renal fibrosis. Although apigenin has been demonstrated to play a protective role from fibrotic diseases, its pharmacological effect on renal fibroblast activation remains largely unknown.

MATERIALS AND METHODS

Here, we examined the functional role of apigenin in the activation of renal fibroblasts response to transforming growth factor (TGF)-β1 and its potential mechanisms. Cultured renal fibroblasts (NRK-49F) were exposed to apigenin (1, 5, 10 and 20 μM), followed by the stimulation of TGF-β1 (2 ng/mL) for 24 h. The markers of fibroblast activation were determined. In order to confirm the anti-fibrosis effect of apigenin, the expression of fibrosis-associated genes in renal fibroblasts was assessed. As a consequence, apigenin alleviated fibroblast proliferation and fibroblastmyofibroblast differentiation induced by TGF-β1.

RESULTS

Notably, apigenin significantly inhibited the fibrosis-associated genes expression in renal fibroblasts. Moreover, apigenin treatment significantly increased the phosphorylation of AMP-activated protein kinase (AMPK). Apigenin treatment also obviously reduced TGF-β1 induced phosphorylation of ERK1/2 but not Smad2/3, p38 and JNK MAPK in renal fibroblasts.

CONCLUSION

In a summary, these results indicate that apigenin inhibits renal fibroblast proliferation, differentiation and function by AMPK activation and reduced ERK1/2 phosphorylation, suggesting it could be an attractive therapeutic potential for the treatment of renal fibrosis.

Peptide DR8 suppresses epithelial-to-mesenchymal transition via the TGF-β/MAPK signaling pathway in renal fibrosis

AIMS

Renal fibrosis is a progressive disease that leads to renal dysfunction and end-stage renal failure, and there is currently no specific treatment. Our previous study showed that the 8-residue peptide DR8 (DHNNPQIR) exhibits potent antioxidant and antifibrotic properties, and accumulating evidence suggests that oxidative stress contributes greatly to fibrosis. The effects and mechanisms of DR8 on renal fibrosis remain unknown.

MATERIALS AND METHODS

The effects of DR8 were assessed in a unilateral ureteral obstruction mouse model that received a daily, single-dose subcutaneous injection of 500 μg/kg DR8 for 14 days and in cultured cells (HK-2 and NIH-3T3 cells) treated with 5 ng/mL TGF-β1 and 80 μM DR8. Western blotting, immunohistochemical staining, real-time qPCR and other tools were conducted to study the molecular mechanisms underlying antifibrotic effects.

KEY FINDINGS

DR8 improved renal function and reduced injury and extracellular matrix (ECM) deposition. Inflammation and oxidative stress were alleviated by DR8 in vivo. DR8 also inhibited the activation of fibroblasts and ECM deposition in HK-2 and NIH-3T3 cells induced by TGF-β1. In addition, epithelial-to-mesenchymal transition (EMT) was inhibited by DR8 both in vivo and in vitro. Mechanistic studies supported that DR8 inhibited ERK and p38 mitogen-activated protein kinase (MAPK) activation. These results indicate that DR8 attenuates renal fibrosis via suppression of EMT by antagonizing the MAPK pathway.

SIGNIFICANCE

We provide mechanistic details for a potential therapeutic agent and establish a foundation for peptide therapeutics.

Pulmonary fibrosis and COVID-19: the potential role for antifibrotic therapy

In December, 2019, reports emerged from Wuhan, China, of a severe acute respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). By the end of April, 2020, over 3 million people had been confirmed infected, with over 1 million in the USA alone, and over 215 000 deaths. The symptoms associated with COVID-19 are diverse, ranging from mild upper respiratory tract symptoms to severe acute respiratory distress syndrome. The major risk factors for severe COVID-19 are shared with idiopathic pulmonary fibrosis (IPF), namely increasing age, male sex, and comorbidities such as hypertension and diabetes. However, the role of antifibrotic therapy in patients with IPF who contract SARS-CoV-2 infection, and the scientific rationale for their continuation or cessation, is poorly defined. Furthermore, several licensed and potential antifibrotic compounds have been assessed in models of acute lung injury and viral pneumonia. Data from previous coronavirus infections such as severe acute respiratory syndrome and Middle East respiratory syndrome, as well as emerging data from the COVID-19 pandemic, suggest there could be substantial fibrotic consequences following SARS-CoV-2 infection. Antifibrotic therapies that are available or in development could have value in preventing severe COVID-19 in patients with IPF, have the potential to treat severe COVID-19 in patients without IPF, and might have a role in preventing fibrosis after SARS-CoV-2 infection.

The Emerging Role of Innate Immunity in Chronic Kidney Diseases

Renal fibrosis is a common fate of chronic kidney diseases. Emerging studies suggest that unsolved inflammation will progressively transit into tissue fibrosis that finally results in an irreversible end-stage renal disease (ESRD). Renal inflammation recruits and activates immunocytes, which largely promotes tissue scarring of the diseased kidney. Importantly, studies have suggested a crucial role of innate immunity in the pathologic basis of kidney diseases. This review provides an update of both clinical and experimental information, focused on how innate immune signaling contributes to renal fibrogenesis. A better understanding of the underlying mechanisms may uncover a novel therapeutic strategy for ESRD.

Comprehensive molecular characterization of circRNA-associated ceRNA network in constrictive pericarditis

Background

Aberrant gene expression occurs in almost all diseases including constrictive pericarditis (CP). However, the dysregulation of genes underlying the CP remains unclear. This study aims to investigate the potential molecular mechanisms underlying CP and screen hub genes critical for the pathogenesis of CP.

Methods

Differentially expressed mRNAs, miRNAs, lncRNAs and circRNAs in pericardial tissues were screened using RNA-seq in CP patients and controls. Furthermore, functional annotation analysis and protein-protein interaction (PPI) network were carried out to investigate the potential key pathways and identify hub genes in CP. Subsequently, a ceRNA network was established and the key circRNAs were determined by Gene Set Enrichment Analysis (GSEA). Finally, the corresponding RNA-seq results were confirmed and validated with a quantitative real time-PCR (qRT-PCR).

Results

Functional annotation analysis revealed that differentially expressed mRNAs (DEMs) mainly participated in inflammatory response related pathways and the 10 top genes with the highest degree in PPI network were considered as the hub genes. In addition, a total of 377 regulatory relationships among the differentially expressed genes (DEGs) could be constructed, from which a subsequent ceRNA network was also established, while the circRNAs were further validated with qRT-PCR and the key biological pathways were identified using GSEA as well.

Conclusions

The genes determined to have altered expression levels in CP may participate in a number of biological signaling processes leading to inflammation and fibrosis frequently encountered in CP, and, therefore, our novel findings may provide an insight into the pathogenesis, molecular biomarkers, and potential therapeutic targets in CP.

Heterotrimeric Gα12/13 proteins in kidney injury and disease

Gα₁₂ and Gα₁₃ are ubiquitous members of the heterotrimeric guanine nucleotide-binding protein (G protein) family that play central and integrative roles in the regulation of signal transduction cascades within various cell types in the kidney. Gα₁₂/Gα₁₃ proteins enable the kidney to adapt to an ever-changing environment by transducing stimuli from cell surface receptors and accessory proteins to effector systems. Therefore, perturbations in Gα₁₂/Gα₁₃ levels or their activity can contribute to the pathogenesis of various renal diseases, including renal cancer. This review will highlight and discuss the complex and expanding roles of Gα₁₂/Gα₁₃ proteins on distinct renal pathologies, with emphasis on more recently reported findings. Deciphering how the different Gα₁₂/Gα₁₃ interaction networks participate in the onset and development of renal diseases may lead to the discovery of new therapeutic strategies.

Mitogen-Activated Protein Kinase Inhibitors and T-Cell-Dependent Immunotherapy in Cancer

Mitogen-activated protein kinase (MAPK) signaling networks serve to regulate a wide range of physiologic and cancer-associated cell processes. For instance, a variety of oncogenic mutations often lead to hyperactivation of MAPK signaling, thereby enhancing tumor cell proliferation and disease progression. As such, several components of the MAPK signaling network have been proposed as viable targets for cancer therapy. However, the contributions of MAPK signaling extend well beyond the tumor cells, and several MAPK effectors have been identified as key mediators of the tumor microenvironment (TME), particularly with respect to the local immune infiltrate. In fact, a blockade of various MAPK signals has been suggested to fundamentally alter the interaction between tumor cells and T lymphocytes and have been suggested a potential adjuvant to immune checkpoint inhibition in the clinic. Therefore, in this review article, we discuss the various mechanisms through which MAPK family members contribute to T-cell biology, as well as circumstances in which MAPK inhibition may potentiate or limit cancer immunotherapy.

Combined Blockade of Smad3 and JNK Pathways Ameliorates Progressive Fibrosis in Folic Acid Nephropathy

Acute kidney injury leading to chronic kidney disease through tubulointerstitial fibrosis is a major challenge in nephropathy. Several signaling pathways promote interstitial fibrosis; however, effective suppression of fibrosis may require blockade of more than one pathway. This study investigated whether blockade of Smad3 and c-Jun N-terminal kinase (JNK) signaling gives added suppression of interstitial fibrosis in folic acid nephropathy. A single high dose of folic acid (FA) causes acute tubular damage in C57BL/6J mice followed by interstitial fibrosis and chronic renal impairment. Co-activations of Smad3 and JNK signaling occur in both tubular epithelial cells and myofibroblasts in areas of tubulointerstitial damage and fibrosis in both murine FA-induced nephropathy and human IgA nephropathy. Groups of mice were treated with a Smad3 inhibitor (SIS3), a JNK inhibitor (SP600125), or a combination from day 6 after FA administration until being killed on day 28. Each drug efficiently inhibited its specific target (Smad3 phosphorylation or c–Jun phosphorylation) without affecting the other pathway. Given alone, each drug partially reduced renal fibrosis, whereas the combination therapy gave an additive and profound protection from renal fibrosis and improved renal function. Inhibition of Smad3 and/or JNK signaling activities prevented down-regulation of PGC-1α in tubular epithelial cells and up-regulation of PGC-1α in myofibroblasts during FA-induced renal fibrosis and inflammation. The expression of PGC-1α was upregulated in Smad3^−/− NRK52E cells while downregulated in Smad3^−/−NRK49F cells, suggesting that Smad3 signaling may regulate expression of PGC-1α in renal tubular epithelial cells and fibroblasts in distinct fashion. In vivo and cell culture studies also indicate that Smad3 and JNK signaling cooperate to cause mitochondrial dysfunction and cell damage in tubular epithelial cells via direct actions on the transcription of PGC-1α. These pathways also act cooperatively to promote renal fibroblast proliferation in tempo-spatial fashion. In conclusion, we have identified a potential combination therapy for progressive renal fibrosis which operates, in part, through modifying mitochondrial function.