Tubular-specific expression of HIV protein Vpr leads to severe tubulointerstitial damage accompanied by progressive fibrosis and cystic development.

Chronic kidney disease (CKD) is a common cause of morbidity in human immunodeficiency virus (HIV)-positive individuals. HIV infection leads to a wide spectrum of kidney cell damage, including tubular epithelial cell (TEC) injury. Among the HIV-1 proteins, the pathologic effects of viral protein R (Vpr) are well established and include DNA damage response, cell cycle arrest, and cell death. Several in vitro studies have unraveled the molecular pathways driving the cytopathic effects of Vpr in tubular epithelial cells. However, the in vivo effects of Vpr on tubular injury and CKD pathogenesis have not been thoroughly investigated. Here, we use a novel inducible tubular epithelial cell-specific Vpr transgenic mouse model to show that Vpr expression leads to progressive tubulointerstitial damage, interstitial inflammation and fibrosis, and tubular cyst development. Importantly, Vpr-expressing tubular epithelial cells displayed significant hypertrophy, aberrant cell division, and atrophy; all reminiscent of tubular injuries observed in human HIV-associated nephropathy (HIVAN). Single-cell RNA sequencing analysis revealed the Vpr-mediated transcriptomic responses in specific tubular subsets and highlighted the potential multifaceted role of p53 in the regulation of cell metabolism, proliferation, and death pathways in Vpr-expressing tubular epithelial cells. Thus, our study demonstrates that HIV Vpr expression in tubular cells is sufficient to induce HIVAN-like tubulointerstitial damage and fibrosis, independent of glomerulosclerosis and proteinuria. Additionally, as this new mouse model develops progressive CKD with diffuse fibrosis and kidney failure, it can serve as a useful tool to examine the mechanisms of kidney disease progression and fibrosis in vivo.

Optical and Photocatalytic Properties of Cobalt-Doped LuFeO3 Powders Prepared by Oxalic Acid Assistance.

B-site cobalt (Co)-doped rare-earth orthoferrites ReFeO3 have shown considerable enhancement in physical properties compared to their parent counterparts, and Co-doped LuFeO3 has rarely been reported. In this work, LuFe1-xCoxO3 (x = 0, 0.05, 0.1, 0.15) powders have been successfully prepared by a mechanochemical activation-assisted solid-state reaction (MAS) method at 1100 °C for 2 h. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy studies demonstrated that a shrinkage in lattice parameters emerges when B-site Fe ions are substituted by Co ions. The morphology and elemental distribution were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The UV-visible absorbance spectra show that LuFe0.85Co0.15O3 powders have a narrower bandgap (1.75 eV) and higher absorbance than those of LuFeO3 (2.06 eV), obviously improving the light utilization efficiency. Additionally, LuFe0.85Co0.15O3 powders represent a higher photocatalytic capacity than LuFeO3 powders and can almost completely degrade MO in 5.5 h with the assistance of oxalic acid under visible irradiation. We believe that the present study will promote the application of orthorhombic LuFeO3 in photocatalysis.

Reticulon-1A mediates diabetic kidney disease progression through endoplasmic reticulum-mitochondrial contacts in tubular epithelial cells.

Recent epidemiological studies suggest that some patients with diabetes progress to kidney failure without significant albuminuria and glomerular injury, suggesting a critical role of kidney tubular epithelial cell (TEC) injury in diabetic kidney disease (DKD) progression. However, the major risk factors contributing to TEC injury and progression in DKD remain unclear. We previously showed that expression of endoplasmic reticulum-resident protein Reticulon-1A (RTN1A) increased in human DKD, and the increased RTN1A expression promoted TEC injury through endoplasmic reticulum (ER) stress response. Here, we show that TEC-specific RTN1A overexpression worsened DKD in mice, evidenced by enhanced tubular injury, tubulointerstitial fibrosis, and kidney function decline. But RTN1A overexpression did not exacerbate diabetes-induced glomerular injury or albuminuria. Notably, RTN1A overexpression worsened both ER stress and mitochondrial dysfunction in TECs under diabetic conditions by regulation of ER-mitochondria contacts. Mechanistically, ER-bound RTN1A interacted with mitochondrial hexokinase-1 and the voltage-dependent anion channel-1 (VDAC1), interfering with their association. This disengagement of VDAC1 from hexokinase-1 resulted in activation of apoptotic and inflammasome pathways, leading to TEC injury and loss. Thus, our observations highlight the importance of ER-mitochondrial crosstalk in TEC injury and the salient role of RTN1A-mediated ER-mitochondrial contact regulation in DKD progression.

Inhibition of HIPK2 Alleviates Thoracic Aortic Disease in Mice With Progressively Severe Marfan Syndrome.

Objective: Despite considerable research, the goal of finding nonsurgical remedies against thoracic aortic aneurysm and acute aortic dissection remains elusive. We sought to identify a novel aortic PK (protein kinase) that can be pharmacologically targeted to mitigate aneurysmal disease in a well-established mouse model of early-onset progressively severe Marfan syndrome (MFS). Approach and Results: Computational analyses of transcriptomic data derived from the ascending aorta of MFS mice predicted a probable association between thoracic aortic aneurysm and acute aortic dissection development and the multifunctional, stress-activated HIPK2 (homeodomain-interacting protein kinase 2). Consistent with this prediction, Hipk2 gene inactivation significantly extended the survival of MFS mice by slowing aneurysm growth and delaying transmural rupture. HIPK2 also ranked among the top predicted PKs in computational analyses of DEGs (differentially expressed genes) in the dilated aorta of 3 MFS patients, which strengthened the clinical relevance of the experimental finding. Additional in silico analyses of the human and mouse data sets identified the TGF (transforming growth factor)-ß/Smad3 signaling pathway as a potential target of HIPK2 in the MFS aorta. Chronic treatment of MFS mice with an allosteric inhibitor of HIPK2-mediated stimulation of Smad3 signaling validated this prediction by mitigating thoracic aortic aneurysm and acute aortic dissection pathology and partially improving aortic material stiffness. Conclusions: HIPK2 is a previously unrecognized determinant of aneurysmal disease and an attractive new target for antithoracic aortic aneurysm and acute aortic dissection multidrug therapy.

Low expression of HIV genes in podocytes accelerates the progression of diabetic kidney disease in mice.

With the widespread use combination antiretroviral therapy, there has been a dramatic decrease in HIV-associated nephropathy. However, although the patients living with HIV have low or undetectable viral load, the prevalence of chronic kidney disease (CKD) in this population remains high. Additionally, improved survival is associated with aging-related comorbidities such as diabetes and cardiovascular disease. A faster progression of CKD is associated with concurrent HIV infection and diabetes than with HIV infection or diabetes alone. To explore the potential pathogenic mechanisms that synergistically drive CKD progression by diabetes and HIV infection, we generated a new mouse model with a relatively low expression of HIV-1 proviral genes specifically in podocytes (pod-HIV mice) to better mimic the setting of kidney injury in patients living with HIV. While no apparent kidney phenotypes were observed at baseline in pod-HIV mice, the induction of mild diabetic kidney disease with streptozotocin led to significant worsening of albuminuria, glomerular injury, podocyte loss, and kidney dysfunction as compared to the mice with diabetes alone. Mechanistically, diabetes and HIV-1 synergistically increased the glomerular expression of microRNA-34a (miR-34a), thereby reducing the expression of Sirtuin-1 (SIRT1) deacetylase. These changes were also associated with increased acetylation and activation of p53 and p65 NF-κB and with enhanced expression of senescence and inflammatory markers. The treatment of diabetic pod-HIV mice with the specific Sirtuin-1 agonist BF175 significantly attenuated albuminuria and glomerulopathy. Thus, our study highlights the reduction in Sirtuin-1 as a major basis of CKD progression in diabetic patients living with HIV and suggests Sirtuin-1 agonists as a potential therapy.

Expression of Endothelial Cell Injury Marker Cd146 Correlates with Disease Severity and Predicts the Renal Outcomes in Patients with Diabetic Nephropathy.

BACKGROUND/AIMS: Glomerular endothelial cell injury plays a crucial role in the development of diabetic nephropathy (DN). CD146, an endothelial marker, was shown to increase in chronic kidney disease (CKD), but its role in DN remains unknown. We aim to assess whether CD146 could be used to evaluate disease severity and predict renal outcomes in DN at early stages. METHODS: 159 non-dialysis type 2-DN patients from 2008 to 2015 were enrolled to measure the plasma concentration of soluble CD146 (sCD146). 94 type 2 diabetes mellitus patients without DN and 100 healthy subjects were used as controls. The patients with CKD stage 1-3 were referred as early stage patients. Another independent cohort of 48 patients with biopsy-proved DN was used for the immunohistochemistry study of CD146. Renal outcomes were defined as doubling of serum creatinine, initiation of renal replacement therapy or death. RESULTS: We found that plasma level of sCD146 was upregulated and associated with renal function in DN patients. sCD146 was proved to be a more optimal marker than urine albumin creatinine ratio to evaluate disease severity in these DN patients. The kidney expression of CD146 was co-localized with endothelial marker CD31 and increased in DN. CD146 staining in kidney was correlated with the severity of pathological changes in DN patients. Survival analysis suggested that both plasma and biopsy expression of CD146 were correlated with renal outcomes. CONCLUSIONS: CD146 is associated with kidney injury and could be a good marker to predict renal outcomes in patients with early stages of DN.

A Novel Inhibitor of Homeodomain Interacting Protein Kinase 2 Mitigates Kidney Fibrosis through Inhibition of the TGF-ß1/Smad3 Pathway.

Homeodomain interacting protein kinase 2 (HIPK2) is a critical regulator of multiple profibrotic pathways, including that of TGF-ß1/Smad3. Genetic ablation of HIPK2 was shown previously to significantly reduce renal fibrosis in the experimental unilateral ureteral obstruction model and Tg26 mice, a model of HIV-associated nephropathy. To develop specific pharmacologic inhibitors of HIPK2 for antifibrotic therapy, we designed and synthesized small molecule inhibitor compounds on the basis of the predicted structure of HIPK2. Among these compounds, we identified one, BT173, that strongly inhibited the ability of HIPK2 to potentiate the downstream transcriptional activity of Smad3 in kidney tubular cells. Notably, binding of BT173 to HIPK2 did not inhibit HIPK2 kinase activity but rather, interfered allosterically with the ability of HIPK2 to associate with Smad3. In vitro, treatment with BT173 inhibited TGF-ß1-induced Smad3 phosphorylation and Smad3 target gene expression in human renal tubular epithelial cells. In vivo, administration of BT173 decreased Smad3 phosphorylation and mitigated renal fibrosis and deposition of extracellular matrix in unilateral ureteral obstruction and Tg26 mouse models of renal fibrosis. Our data indicate that BT173 is a novel HIPK2 inhibitor that attenuates renal fibrosis through suppression of the TGF-ß1/Smad3 pathway and may be developed as an antifibrotic therapy in patients with kidney disease.

Inhibition of Reticulon-1A-Mediated Endoplasmic Reticulum Stress in Early AKI Attenuates Renal Fibrosis Development.

Several animal studies have shown an important role for endoplasmic reticulum (ER) stress in AKI, whereas human studies are lacking. We recently reported that Reticulon-1A (RTN1A) is a key mediator of ER stress and kidney cell injury. Here, we investigated whether modulation of RTN1A expression during AKI contributes to the progression to CKD. In a retrospective study of 51 patients with AKI, increased expression of RTN1A and other ER stress markers were associated with the severity of kidney injury and with progression to CKD. In an inducible tubular cell-specific RTN1A-knockdown mouse model subjected to folic acid nephropathy (FAN) or aristolochic acid nephropathy, reduction of RTN1A expression during the initial stage of AKI attenuated ER stress and kidney cell injury in early stages and renal fibrosis development in later stages. Treatment of wild-type mice with tauroursodeoxycholic acid, an inhibitor of ER stress, after the induction of kidney injury with FA facilitated renoprotection similar to that observed in RTN1A-knockdown mice. Conversely, in transgenic mice with inducible tubular cell-specific overexpression of RTN1A subjected to FAN, induction of RTN1A overexpression aggravated ER stress and renal injury at the early stage and renal fibrosis at the late stage of FAN. Together, our human and mouse data suggest that the RTN1A-mediated ER stress response may be an important determinant in the severity of AKI and maladaptive repair that may promote progression to CKD.

Genomic Analysis of Kidney Allograft Injury Identifies Hematopoietic Cell Kinase as a Key Driver of Renal Fibrosis.

Renal fibrosis is the common pathway of progression for patients with CKD and chronic renal allograft injury (CAI), but the underlying mechanisms remain obscure. We performed a meta-analysis in human kidney biopsy specimens with CAI, incorporating data available publicly and from our Genomics of Chronic Renal Allograft Rejection study. We identified an Src family tyrosine kinase, hematopoietic cell kinase (Hck), as upregulated in allografts in CAI. Querying the Kinase Inhibitor Resource database revealed that dasatinib, a Food and Drug Administration-approved drug, potently binds Hck with high selectivity. In vitro, Hck overexpression activated the TGF-ß/Smad3 pathway, whereas HCK knockdown inhibited it. Treatment of tubular cells with dasatinib reduced the expression of Col1a1 Dasatinib also reduced proliferation and α-SMA expression in fibroblasts. In a murine model with unilateral ureteric obstruction, pretreatment with dasatinib significantly reduced the upregulation of profibrotic markers, phosphorylation of Smad3, and renal fibrosis observed in kidneys pretreated with vehicle alone. Dasatinib treatment also improved renal function, reduced albuminuria, and inhibited expression of profibrotic markers in animal models with lupus nephritis and folic acid nephropathy. These data suggest that Hck is a key mediator of renal fibrosis and dasatinib could be developed as an antifibrotic drug.

Aldose reductase mediates endothelial cell dysfunction induced by high uric acid concentrations.

BACKGROUND: Uric acid (UA) is an antioxidant found in human serum. However, high UA levels may also have pro-oxidant functions. According to previous research, aldose reductase (AR) plays a vital role in the oxidative stress-related complications of diabetes. We sought to determine the mechanism by which UA becomes deleterious at high concentrations as well as the effect of AR in this process. METHOD: Endothelial cells were divided into three groups cultured without UA or with 300 µM or 600 µM UA. The levels of total reactive oxygen species (ROS), of four ROS components, and of NO and NOX4 expression were measured. Changes in the above molecules were detected upon inhibiting NOX4 or AR, and serum H2O2 and vWF levels were measured in vivo. RESULTS: Increased AR expression in high UA-treated endothelial cells enhanced ROS production by activating NADPH oxidase. These effects were blocked by the AR inhibitor epalrestat. 300 µM UA decreased the levels of the three major reactive oxygen species (ROS) components: O2•-, •OH, and 1O2. However, when the UA concentration was increased, both O2•- levels and downstream H2O2 production significantly increased. Finally, an AR inhibitor reduced H2O2 production in hyperuricemic mice and protected endothelial cell function. CONCLUSIONS: Our findings indicate that inhibiting AR or degrading H2O2 could protect endothelial function and maintain the antioxidant activities of UA. These findings provide new insight into the role of UA in chronic kidney disease.