Yifei Zhong

Down-regulation of NF-κB Transcriptional Activity in HIV-associated Kidney Disease by BRD4 Inhibition

Background: NF-κB and BRD4 control proinflammatory gene activation in HIV-associated kidney disease. Results: Small molecule inhibition of BRD4 binding to NF-κB blocks target gene activation. Conclusion: Targeting the proinflammatory activity of NF-κB may be a new therapeutic approach. Significance: This study has broad implications as NF-κB-mediated inflammation represents the major pathology in chronic kidney and non-kidney diseases. NF-κB-mediated inflammation is the major pathology in chronic kidney diseases, including HIV-associated nephropathy (HIVAN) that ultimately progresses to end stage renal disease. HIV infection in the kidney induces NF-κB activation, leading to the production of proinflammatory chemokines, cytokines, and adhesion molecules. In this study, we explored selective inhibition of NF-κB transcriptional activity by small molecule blocking NF-κB binding to the transcriptional cofactor BRD4, which is required for the assembly of the productive transcriptional complex comprising positive transcription elongation factor b and RNA polymerase II. We showed that our BET (Bromodomain and Extra-Terminal domain)-specific bromodomain inhibitor MS417, designed to block BRD4 binding to the acetylated NF-κB, effectively attenuates NF-κB transcriptional activation of proinflammatory genes in kidney cells treated with TNFα or infected by HIV. MS417 ameliorates inflammation and kidney injury in HIV-1 transgenic mice, an animal model for HIVAN. Our study suggests that BET bromodomain inhibition, targeting at the proinflammatory activity of NF-κB, represents a new therapeutic approach for treating NF-κB-mediated inflammation and kidney injury in HIVAN.

A systems approach identifies HIPK2 as a key regulator of kidney fibrosis.

Kidney fibrosis is a common process that leads to the progression of various types of kidney disease. We used an integrated computational and experimental systems biology approach to identify protein kinases that regulate gene expression changes in the kidneys of human immunodeficiency virus (HIV) transgenic mice (Tg26 mice), which have both tubulointerstitial fibrosis and glomerulosclerosis. We identified homeo-domain interacting protein kinase 2 (HIPK2) as a key regulator of kidney fibrosis. HIPK2 was upregulated in the kidneys of Tg26 mice and in those of patients with various kidney diseases. HIV infection increased the protein concentrations of HIPK2 by promoting oxidative stress, which inhibited the seven in absentia homolog 1 (SIAH1)-mediated proteasomal degradation of HIPK2. HIPK2 induced apoptosis and the expression of epithelial-to-mesenchymal transition markers in kidney epithelial cells by activating the p53, transforming growth factor β (TGF-β)–SMAD family member 3 (Smad3) and Wnt-Notch pathways. Knockout of HIPK2 improved renal function and attenuated proteinuria and kidney fibrosis in Tg26 mice, as well as in other murine models of kidney fibrosis. We therefore conclude that HIPK2 is a potential target for anti-fibrosis therapy.

Role of Transcription Factor Acetylation in Diabetic Kidney Disease

Nuclear factor (NF)-κB and signal transducer and activator of transcription 3 (STAT3) play a critical role in diabetic nephropathy (DN). Sirtuin-1 (SIRT1) regulates transcriptional activation of target genes through protein deacetylation. Here, we determined the roles of Sirt1 and the effect of NF-κB (p65) and STAT3 acetylation in DN. We found that acetylation of p65 and STAT3 was increased in both mouse and human diabetic kidneys. In human podocytes, advanced glycation end products (AGEs) induced p65 and STAT3 acetylation and overexpression of acetylation-incompetent mutants of p65 and STAT3 abrogated AGE-induced expression of NF-κB and STAT3 target genes. Inhibition of AGE formation in db/db mice by pyridoxamine treatment attenuated proteinuria and podocyte injury, restored SIRT1 expression, and reduced p65 and STAT3 acetylation. Diabetic db/db mice with conditional deletion of SIRT1 in podocytes developed more proteinuria, kidney injury, and acetylation of p65 and STAT3 compared with db/db mice without SIRT1 deletion. Treatment of db/db mice with a bromodomain and extraterminal (BET)-specific bromodomain inhibitor (MS417) which blocks acetylation-mediated association of p65 and STAT3 with BET proteins, attenuated proteinuria, and kidney injury. Our findings strongly support a critical role for p65 and STAT3 acetylation in DN. Targeting protein acetylation could be a potential new therapy for DN.

Therapeutic use of traditional Chinese herbal medications for chronic kidney diseases

Traditional Chinese herbal medications (TCHM) are frequently used in conjunction with western pharmacotherapy for treatment of chronic kidney diseases (CKD) in China and many other Asian countries. The practice of traditional Chinese medicine is guided by cumulative empiric experience. Recent in vitro and animal studies have confirmed the biological activity and therapeutic effects of several TCHM in CKD. However, the level of evidence supporting TCHM is limited to small, non-randomized trials. Due to variations in the prescription pattern of TCHM and the need for frequent dosage adjustment, which are inherent to the practice of traditional Chinese medicine, it has been challenging to design and implement large randomized clinical trials of TCHM. Several TCHM are associated with significant adverse effects, including nephrotoxicity. However, reporting of adverse effects associated with TCHM has been inadequate. To fully realize the therapeutic use of TCHM in CKD we need molecular studies to identify active ingredients of TCHM and their mechanism of action, rigorous pharmacologic studies to determine the safety and meet regulatory standards required for clinical therapeutic agents, and well-designed clinical trials to provide evidence-based support of their safety and efficacy.

Expression of HIV transgene aggravates kidney injury in diabetic mice

With the widespread use of combination antiretroviral agents, the incidence of HIV-associated nephropathy has decreased. Currently, HIV-infected patients live much longer and often suffer from comorbidities such as diabetes mellitus. Recent epidemiological studies suggest that concurrent HIV infection and diabetes mellitus may have a synergistic effect on the incidence of chronic kidney disease. To address this, we determined whether HIV-1 transgene expression accelerates diabetic kidney injury using a diabetic HIV-1 transgenic (Tg26) murine model. Diabetes was initially induced with low-dose streptozotocin in both Tg26 and wild-type mice on a C57BL/6 background, which is resistant to classic HIV-associated nephropathy. Although diabetic nephropathy is minimally observed on the C57BL/6 background, diabetic Tg26 mice exhibited a significant increase in glomerular injury compared with nondiabetic Tg26 mice and diabetic wild-type mice. Validation of microarray gene expression analysis from isolated glomeruli showed a significant upregulation of proinflammatory pathways in diabetic Tg26 mice. Thus, our study found that expression of HIV-1 genes aggravates diabetic kidney disease.

Puerarin Attenuated Early Diabetic Kidney Injury through Down-Regulation of Matrix Metalloproteinase 9 in Streptozotocin-Induced Diabetic Rats

Radix puerariae, a traditional Chinese herbal medication, has been used successfully to treat patients with early stage of diabetic nephropathy. However, the underlined mechanism of this renal protective effect has not been determined. In the current study, we investigated the effects and the mechanism of puerarin in Streptozotocin (STZ)-induced diabetic rats. We treated STZ-rats with either puerarin or losartan, an angiotensin II receptor blocker, as compared to those treated with vehicle. We found that both puerarin and losartan attenuated kidney hypertrophy, mesangial expansion, proteinuria, and podocyte foot process effacement in STZ rats. In addition, both puerarin and losartan increased expression of podocyte slit diaphragm proteins such as nephrin and podocin. Interestingly, we found that puerarin treatment induced a more pronounced suppression of oxidative stress production and S-nitrosylation of proteins in the diabetic kidneys as compared to losartan treatment. Furthermore, we found that matrix metalloproteinase-9 (MMP-9), which is known to be activated by oxidative stress and S-nitrosylation of proteins, was also suppressed more extensively by puerarin than losartan. In conclusion, these data provide for the first time the potential mechanism to support the use of puerarin in the treatment of early diabetic nephropathy.

Renoprotective Effect of Combined Inhibition of Angiotensin-Converting Enzyme and Histone Deacetylase

The Connectivity Map database contains microarray signatures of gene expression derived from approximately 6000 experiments that examined the effects of approximately 1300 single drugs on several human cancer cell lines. We used these data to prioritize pairs of drugs expected to reverse the changes in gene expression observed in the kidneys of a mouse model of HIV-associated nephropathy (Tg26 mice). We predicted that the combination of an angiotensin-converting enzyme (ACE) inhibitor and a histone deacetylase inhibitor would maximally reverse the disease-associated expression of genes in the kidneys of these mice. Testing the combination of these inhibitors in Tg26 mice revealed an additive renoprotective effect, as suggested by reduction of proteinuria, improvement of renal function, and attenuation of kidney injury. Furthermore, we observed the predicted treatment-associated changes in the expression of selected genes and pathway components. In summary, these data suggest that the combination of an ACE inhibitor and a histone deacetylase inhibitor could have therapeutic potential for various kidney diseases. In addition, this study provides proof-of-concept that drug-induced expression signatures have potential use in predicting the effects of combination drug therapy.

Novel retinoic acid receptor alpha agonists for treatment of kidney disease.

Development of pharmacologic agents that protect podocytes from injury is a critical strategy for the treatment of kidney glomerular diseases. Retinoic acid reduces proteinuria and glomerulosclerosis in multiple animal models of kidney diseases. However, clinical studies are limited because of significant side effects of retinoic acid. Animal studies suggest that all trans retinoic acid (ATRA) attenuates proteinuria by protecting podocytes from injury. The physiological actions of ATRA are mediated by binding to all three isoforms of the nuclear retinoic acid receptors (RARs): RARα, RARβ, and RARγ. We have previously shown that ATRA exerts its renal protective effects mainly through the agonism of RARα. Here, we designed and synthesized a novel boron-containing derivative of the RARα-specific agonist Am580. This new derivative, BD4, binds to RARα receptor specifically and is predicted to have less toxicity based on its structure. We confirmed experimentally that BD4 binds to RARα with a higher affinity and exhibits less cellular toxicity than Am580 and ATRA. BD4 induces the expression of podocyte differentiation markers (synaptopodin, nephrin, and WT-1) in cultured podocytes. Finally, we confirmed that BD4 reduces proteinuria and improves kidney injury in HIV-1 transgenic mice, a model for HIV-associated nephropathy (HIVAN). Mice treated with BD4 did not develop any obvious toxicity or side effect. Our data suggest that BD4 is a novel RARα agonist, which could be used as a potential therapy for patients with kidney disease such as HIVAN.

Efficacy and Safety of Traditional Chinese Medicine (Shenqi Particle) for Patients With Idiopathic Membranous Nephropathy: A Multicenter Randomized Controlled Clinical Trial

BACKGROUND To compare the safety and efficacy of the traditional Chinese medicine Shenqi particle and standard therapy with prednisone and cyclophosphamide (control) in adult patients with idiopathic membranous nephropathy (IMN). STUDY DESIGN Open-label, multicenter, parallel, randomized, controlled clinical trial. SETTING & PARTICIPANTS From April 2008 to February 2011, a total of 190 patients with biopsy-proven IMN from 7 hospitals in China participated in the study. All patients had nephrotic syndrome with estimated glomerular filtration rate (eGFR) >30 mL/min/1.73 m(2). INTERVENTION Shenqi particle (9.6 g 3 times per day) or prednisone (1 mg/kg/d tapering to 0.17 mg/kg/d) and cyclophosphamide (total dose of 9-12 g per square meter of body surface area) for 48 weeks. OUTCOMES Primary outcomes included complete remission, defined as proteinuria (24-hour urine protein excretion) ≤0.3 g/d, or partial remission, defined as proteinuria with protein excretion >0.3-<3.5 g/d and a 50% reduction from its peak value at 48 weeks. Secondary outcomes included serum albumin level, eGFR, doubling of serum creatinine level, end-stage renal disease, and death. RESULTS Baseline values for proteinuria and eGFR were 5.34 ± 2.74 g/d and 84.0 ± 27.4 mL/min/1.73 m(2) for the Shenqi particle group and 5.33 ± 2.47 g/d and 83.8 ± 24.9 mL/min/1.73 m(2) for the control group, respectively. 132 patients (63 Shenqi particle group, 69 control group) completed the study. Change in urinary protein excretion in the Shenqi particle group was -3.01 (95% CI, -3.68 to -2.34) g/d, and in the control group, -3.28 (95% CI, -3.98 to -2.58) g/d; the mean difference between groups was 0.27 (95% CI, -0.70 to 1.23) g/d (P = 0.6). Changes in eGFR were 12.3 (95% CI, 4.99 to 19.6) mL/min/1.73 m(2) in the Shenqi particle group and -2.8 (95% CI, -10.32 to 4.77) mL/min/1.73 m(2) in the control group; the mean difference between groups was 15.1 (95% CI, 4.56 to 25.55) mL/min/1.73 m(2) (P = 0.005). Severe adverse events occurred in only the control group (14.5%) and included lung infection, liver injury, and pneumonia. LIMITATIONS High rate of loss to follow-up and lack of observation period prior to the study. CONCLUSIONS Shenqi particle may be a promising alternative therapy for adults with IMN and nephrotic syndrome.

Roflumilast enhances the renal protective effects of retinoids in an HIV-1 transgenic mouse model of rapidly progressive renal failure.

Retinoic acid decreases proteinuria and glomerulosclerosis in several animal models of kidney disease by protecting podocytes from injury. Our recent in vitro studies suggest that all-trans retinoic acid induces podocyte differentiation by activating the retinoic acid receptor-α (RARα)/cAMP/PKA/CREB pathway. When used in combination with all-trans retinoic acid, an inhibitor of phosphodiesterase 4 further enhanced podocyte differentiation by increasing intracellular cAMP. Additionally, we found that Am580, a specific RARα agonist, has similar renal protective effects as all-trans retinoic acid in a rederived colony of HIV-1 transgenic mice with rapidly progressive renal failure (HIV-Tg) that mimics human HIV-associated nephropathy. Treatment with either the inhibitor of phoshodiesterase 4, roflumilast, or Am580 significantly reduced proteinuria, attenuated kidney injury, and improved podocyte differentiation in these HIV-Tg mice. Additional renal protective effects were found when roflumilast was combined with Am580. Consistent with the in vitro data, glomeruli from HIV-Tg mice treated with both Am580 and roflumilast had more active phosphorylated CREB than with either agent alone. Thus, phosphodiesterase 4 inhibitors could be used in combination with RARα agonists to provide additional renal protection.