Yufeng Huang

BACKGROUND: Upregulation of the RNA-binding protein HuR (human antigen R) has been reported in patients with chronic kidney disease (CKD), but its pathogenic role remains incompletely understood. We hypothesized that HuR promotes renal and vascular injury in hypertensive CKD and that pharmacological inhibition of HuR attenuates disease progression. We therefore investigated the role of HuR in deoxycorticosterone acetate (DOCA) plus Ang II (angiotensin II)-induced CKD and evaluated the therapeutic efficacy of the HuR inhibitor, KH3 . METHODS: Male mice underwent uninephrectomy followed by DOCA+Ang II infusion with 1% NaCl in drinking water and were treated with KH3 or vehicle for 3 weeks. Control mice received saline without DOCA or Ang II. RESULTS: DOCA+Ang II markedly increased HuR expression in circulating exosomes and kidney tissues, which was attenuated by KH3 treatment. KH3 reduced albuminuria, improved renal function, and attenuated kidney hypertrophy, glomerular, and tubulointerstitial fibrosis. These renoprotective effects were associated with reduced podocyte and tubular injury, decreased macrophage infiltration, and suppression of NF-κB (nuclear factor-kappa B) p65, Nox2 (NADPH oxidase 2), AKT (protein kinase B) phosphorylation, TGFβ1 (transforming growth factor β1), and Wisp1 (WNT1-inducible signaling pathway protein 1) signaling. KH3 also partially lowered arterial blood pressure in DOCA+Ang II–treated mice. Further studies in vascular smooth muscle cells and mesenteric resistance arteries suggested that HuR inhibition may suppress vascular profibrotic signaling associated with SGLT2 (sodium-glucose cotransporter 2). CONCLUSIONS: HuR is upregulated in renal and vascular tissues in DOCA+Ang II–induced CKD and contributes to renal inflammation, oxidative stress, fibrosis, and vascular dysfunction. Pharmacological inhibition of HuR attenuates renal and vascular injury, supporting HuR as a promising therapeutic target for CKD.

Plasma prorenin is commonly elevated in patients with diabetes and has been associated with the development of albuminuria and progression of diabetic nephropathy. Because albuminuria often reflects podocyte injury, the pathogenic role of prorenin in podocyte dysfunction warrants further investigation. In this study, we examined the association between prorenin and podocyte injury, as well as glomerular fibrosis, using a transgenic rat model in which prorenin is inducibly expressed and secreted from the liver. cyp1a1-prorenin transgenic rats were randomized to receive diets containing increasing concentrations of the gene activator indole-3-carbinol (I3C; 0.05%, 0.15%, or 0.3%) for 4 weeks. Wild-type rats maintained on a normal diet served as controls. I3C administration resulted in a dose-dependent increase in plasma prorenin levels in transgenic rats. Elevated prorenin was associated with increased mean arterial pressure and urinary albumin excretion, accompanied by a dose-dependent reduction in podocyte number and slit diaphragm protein expression, as well as segmental foot process effacement and podocyte hypertrophy. In addition, increased prorenin stimulated renal expression of profibrotic factors and promoted glomerular fibrosis. Treatment with either amlodipine or enalapril for 6 weeks prevented the development of hypertension and partially attenuated podocyte injury, albuminuria, and renal fibrosis, without fully reversing these changes. These protective effects were associated with suppression of NF-κB- and Nox2-mediated inflammatory and oxidative stress pathways. Collectively, these findings demonstrate that prorenin promotes podocyte injury and glomerular fibrosis through mechanisms that are partially dependent on hypertension and angiotensin II but also involve angiotensin II-independent pathways.

This study identifies the RNA-binding protein HuR as a key regulator of maladaptive tubular repair during AKI-to-CKD transition. Pharmacologic disruption of HuR-RNA interactions with the small molecule inhibitor KH3 attenuated tubular injury, inflammation, senescence, and fibrosis in aristolochic acid-induced nephropathy. These findings provide mechanistic insight into posttranscriptional control of kidney injury and establish HuR inhibition as a promising therapeutic strategy to prevent CKD progression following AKI.

Background: Elevated RNA-binding protein HuR has been reported in patients with chronic kidney disease (CKD), but its specific pathogenic role remains unclear. Here, we investigated HuR involvement in progressive CKD induced by deoxycorticosterone acetate (DOCA) plus angiotensin II (Ang II) in mice and evaluated the therapeutic efficacy and mechanisms of the HuR inhibitor KH3. Methods: Adult male mice underwent uninephrectomy and were subjected to DOCA + Ang II infusion with 1% NaCl in drinking water. Mice were then treated with KH3 or vehicle for 3 weeks. Control mice received saline injections without DOCA and Ang II infusion. Results: DOCA + Ang II infusion markedly increased HuR expression in circulating exosomes and kidney tissues, which was attenuated by KH3. KH3 halted the progression of albuminuria and improved renal function, and reduced kidney hypertrophy and glomerular and tubulointerstitial fibrosis compared with untreated DOCA + Ang II mice. These improvements were associated with reduced podocyte and tubular injury. KH3 also decreased renal macrophage infiltration and suppressed NF- κBp65, Nox2, AKT phosphorylation, TGF-β1, and Wisp1, consistent with reduced inflammation, oxidative stress, and fibrosis. In addition, KH3 partially lowered arterial blood pressure in DOCA + Ang II-infused mice, an effect that may involve suppression of SGLT2-associated profibrotic vascular responses, as supported by studies in cultured VSMCs and mesenteric resistance arteries. Conclusions: HuR is upregulated in DOCA + Ang II-induced renal and vascular injury and contributes to hypertensive, inflammatory, oxidative, and fibrotic responses in CKD. Pharmacologic inhibition of HuR-RNA interactions represents a promising therapeutic strategy for CKD.

Hemodialysis requires functional vascular access, which serves as the conduit for blood flow between the patient and the hemodialysis machine. The arteriovenous fistula (AVF), created by surgically connecting an artery to a nearby vein in the upper extremity, is the preferred form of vascular access for maintenance hemodialysis. Newly created AVFs must undergo a maturation process, during which the fistula vein enlarges and develops sufficient lumen size and blood flow to be used effectively for dialysis. However, since the invention of AVFs 60 years ago, rates of AVF maturation failure have remained high. Currently, no proven therapies exist to promote maturation or prevent maturation failure. This review examines the current understanding of the cellular and molecular mechanisms underlying AVF maturation failure, with particular focus on the impact of the chronic kidney disease (CKD) environment on the vascular system. In CKD, patients often have elevated levels of uremic toxins, increased oxidative stress, and chronic inflammation, all of which adversely affect the function of vascular wall cells (such as endothelial cells, vascular smooth muscle cells, and fibroblasts) and circulating cells (such as platelets and immune/inflammatory cells). The goal of this review is to explore the mechanisms influencing both native and AVF vasculature in the context of CKD. In addition, we will discuss current therapies aimed at improving native vasculature in patients with CKD, as well as investigational approaches to promote AVF maturation.

Whether combining an sGC activator with an SGLT2 inhibitor could better control diabetes-associated oxidative stress and NO-cGMP signal deficiency has not yet been explored. Using the type 2 diabetic db/db mouse model, this study underscores the sGC activator avenciguat as a novel therapy for diabetic nephropathy and liver injury beyond sGLT2 inhibitors. It also highlights the need for further investigation into the combined effects of these two treatments in managing diabetic complications.

Septic acute kidney injury (AKI) is an important risk factor for developing chronic kidney disease (CKD). Hu antigen R (HuR) is recognized as a crucial modulator in inflammation. We hypothesized that elevated HuR contributes to the transition from septic AKI to CKD by promoting persistent inflammation and fibrosis, and inhibition of HuR may reverse septic kidney injury. Mice subjected to lipopolysaccharide (LPS) injections every other day were concurrently treated without or with either KH39 or niclosamide (NCS) for 7 days. Control mice received saline injections. Repeated LPS injections led to a significant increase in HuR expression in the kidneys, which was effectively suppressed by KH39 or NCS treatment. LPS-induced kidney injury was characterized by elevated plasma blood urea nitrogen levels and urinary albuminuria, along with histological signs of inflammatory cell infiltration and fibrosis, as determined by periodic acid–Schiff and Masson’s trichrome staining, and immunofluorescent staining for markers such as α-smooth muscle actin, fibronectin, collagen III, and F4/80. Treatment with either KH39 or NCS mitigated these changes observed in LPS-injured kidneys. Additionally, increased expression of CD147, a molecule implicated in inflammatory cell recruitment and tubular injury, was inhibited by KH39 or NCS treatment. These effects on HuR and CD147 expression were further validated in vitro in cultured macrophages and tubular cells. This study suggests that HuR elevation in LPS-stimulated macrophages and kidney cells contributes to the progression of septic kidney injury, possibly through HuR-CD147 interactions, underscoring the therapeutic potential of HuR inhibitors for this condition.

Hu antigen R (HuR) plays a key role in regulating genes critical to the pathogenesis of diabetic nephropathy (DN). This study investigates the therapeutic potential of niclosamide (NCS) as an HuR inhibitor in DN. Uninephrectomized mice were assigned to four groups: normal control; untreated db/db mice terminated at 14 and 22 weeks, respectively; and db/db mice treated with NCS (20 mg/kg daily via i.p.) from weeks 18 to 22. Increased HuR expression was observed in diabetic kidneys from db/db mice, which was mitigated by NCS treatment. Untreated db/db mice exhibited obesity, progressive hyperglycemia, albuminuria, kidney hypertrophy and glomerular mesangial matrix expansion, increased renal production of fibronectin and a-smooth muscle actin, and decreased glomerular WT-1⁺-podocytes and nephrin expression. NCS treatment did not affect mouse body weight, but reduced blood glucose and HbA1c levels and halted the DN progression observed in untreated db/db mice. Renal production of inflammatory and oxidative stress markers (NF-κBp65, TNF-a, MCP-1) and urine MDA levels increased during disease progression in db/db mice but were halted by NCS treatment. Additionally, the Wnt1-signaling-pathway downstream factor, Wisp1, was identified as a key downstream mediator of HuR-dependent action and found to be markedly increased in db/db mouse kidneys, which was normalized by NCS treatment. These findings suggest that inhibition of HuR with NCS is therapeutic for DN by improving hyperglycemia, renal inflammation, and oxidative stress. The reduction in renal Wisp1 expression also contributes to its renoprotective effects. This study supports the potential of repurposing HuR inhibitors as a novel therapy for DN.

Background: Upregulation of an RNA-binding protein HuR has been implicated in glomerular diseases. Herein, we evaluated whether it is involved in renal tubular fibrosis. Methods: HuR was firstly examined in human kidney biopsy tissue with tubular disease. Second, its expression and the effect of HuR inhibition with KH3 on tubular injury were further assessed in a mouse model induced by a unilateral renal ischemia/reperfusion (IR). KH3 (50 mg kg⁻¹) was given daily via intraperitoneal injection from day 3 to 14 after IR. Last, one of HuR-targeted pathways was examined in cultured proximal tubular cells. Results: HuR significantly increases at the site of tubular injury both in progressive CKD in patients and in IR-injured kidneys in mice, accompanied by upregulation of HuR targets that are involved in inflammation, profibrotic cytokines, oxidative stress, proliferation, apoptosis, tubular EMT process, matrix remodeling and fibrosis in renal tubulointerstitial fibrosis. KH3 treatment reduces the IR-induced tubular injury and fibrosis, accompanied by the remarkable amelioration in those involved pathways. A panel of mRNA array further revealed that 519 molecules in mouse kidney following IR injury changed their expression and 71.3% of them that are involved in 50 profibrotic pathways, were ameliorated when treated with KH3. In vitro, TGFβ1 induced tubular HuR cytoplasmic translocation and subsequent tubular EMT, which were abrogated by KH3 administration in cultured HK-2 cells. Conclusions: These results suggest that excessive upregulation of HuR contributes to renal tubulointerstitial fibrosis by dysregulating genes involved in multiple profibrotic pathways and activating the TGFß1/HuR feedback circuit in tubular cells. Inhibition of HuR may have therapeutic potential for renal tubular fibrosis.

Although mesenchymal stem cell (MSC)-based regenerative therapy is being developed for the treatment of kidney diseases, cell delivery and engraftment still need to be improved. Cell sheet technology has been developed as a new cell delivery method, to recover cells as a sheet form retaining intrinsic cell adhesion proteins, which promotes its transplantation efficiency to the target tissue. We thus hypothesized that MSC sheets would therapeutically reduce kidney disease with high transplantation efficiency. When the chronic glomerulonephritis was induced by two injections of the anti-Thy 1.1 antibody (OX-7) in rats, the therapeutic efficacy of rat bone marrow stem cell (rBMSC) sheet transplantation was evaluated. The rBMSC-sheets were prepared using the temperature-responsive cell-culture surfaces and transplanted as patches onto the surface of two kidneys of each rat at 24 h after the first injection of OX-7. At 4 weeks, retention of the transplanted MSC-sheets was confirmed, and the animals with MSC-sheets showed significant reductions in proteinuria, glomerular staining for extracellular matrix protein, and renal production of TGFß1, PAI-1, collagen I, and fibronectin. The treatment also ameliorated podocyte and renal tubular injury, as evidenced by a reversal in the reductions of WT-1, podocin, and nephrin and by renal overexpression of KIM-1 and NGAL. Furthermore, the treatment enhanced gene expression of regenerative factors, and IL-10, Bcl-2, and HO-1 mRNA levels, but reduced TSP-1 levels, NF-kB, and NAPDH oxidase production in the kidney. These results strongly support our hypothesis that MSC-sheets facilitated MSC transplantation and function, and effectively retarded progressive renal fibrosis via paracrine actions on anti-cellular inflammation, oxidative stress, and apoptosis and promoted regeneration.