Treatment with quercetin inhibits SARS-CoV-2 N protein-induced acute kidney injury by blocking Smad3-dependent G1 cell-cycle arrest.

Increasing evidence shows that SARS-CoV-2 can infect kidneys and cause acute kidney injury (AKI) in critically ill COVID-19 patients. However, mechanisms through which COVID-19 induces AKI are largely unknown, and treatment remains ineffective. Here, we report that kidney-specific overexpressing SARS-CoV-2 N gene can cause AKI, including tubular necrosis and elevated levels of serum creatinine and BUN in 8-week-old diabetic db/db mice, which become worse in those with older age (16 weeks) and underlying diabetic kidney disease (DKD). Treatment with quercetin, a purified product from traditional Chinese medicine (TCM) that shows effective treatment of COVID-19 patients, can significantly inhibit SARS-CoV-2 N protein-induced AKI in diabetic mice with or without underlying DKD. Mechanistically, quercetin can block the binding of SARS-CoV-2 N protein to Smad3, thereby inhibiting Smad3 signaling and Smad3-mediated cell death via the p16-dependent G1 cell-cycle arrest mechanism in vivo and in vitro. In conclusion, SARS-CoV-2 N protein is pathogenic and can cause severe AKI in diabetic mice, particularly in those with older age and pre-existing DKD, via the Smad3-dependent G1 cell-cycle arrest mechanism. Importantly, we identify that quercetin may be an effective TCM compound capable of inhibiting COVID-19 AKI by blocking SARS-CoV-2 N-Smad3-mediated cell death pathway.

AANG Prevents Smad3-dependent Diabetic Nephropathy by Restoring Pancreatic ß-Cell Development in db/db Mice.

Diabetic nephropathy (DN) is a major cause of end-stage kidney disease, where TGF-ß1/Smad signaling plays an important role in the disease progression. Our previous studies demonstrated a combination of Traditional Chinese Medicine derived Smad7 agonist Asiatic Acid (AA) and Smad3 inhibitor Naringenin (NG), AANG, effectively suppressed the progression of renal fibrosis in vivo. However, its implication in type-2 diabetic nephropathy (T2DN) is still unexplored. Here, we detected progressive activation of Smad3 but reduction of Smad7 in db/db mice during T2DN development. Therefore, we optimized the dosage and the combination ratio of AANG to achieve a better rebalancing Smad3/Smad7 signaling for treatment of T2DN. Unexpectedly, preventive treatment with combined AANG from week 4 before the development of diabetes and T2DN effectively protected against the onset of T2DN. In contract, these inhibitory effects were lost when db/db mice received the late AANG treatment from 12-24 weeks. Surprisingly, preventive treatment with AANG ameliorated not only T2DN but also the primary disease type-2 diabetes (T2D) with relative normal levels of fasting blood glucose and HbA1c, and largely improving metabolic abnormalities especially on insulin insensitivity and glucose tolerance in db/db mice. Mechanistically, AANG effectively prevented both Smad3-mediated renal fibrosis and NF-κB-driven renal inflammation in the diabetic kidney in vivo and advanced glycation end-products (AGE) stimulated tubular epithelial mTEC cells in vitro. More importantly, we uncovered that preventive treatment with AANG effectively protected against diabetic-associated islet injury via restoring the ß cell development in db/db mice. Taken together, we discovered that the early treatment with combined AANG can effectively protect against the development of T2D and T2DN via mechanism associated with protection against Smad3-depenedent islet injury.

Smad3-Targeted Therapy Protects against Cisplatin-Induced AKI by Attenuating Programmed Cell Death and Inflammation via a NOX4-Dependent Mechanism.

BACKGROUND: Transforming growth factor-ß (TGF-ß)/Smad signaling is the central mediator in renal fibrosis, yet its functional role in acute kidney injury (AKI) is not fully understood. Recent evidence showed that TGF-ß/Smad3 may be involved in the pathogenesis of AKI, but its functional role and mechanism of action in cisplatin-induced AKI are unclear. OBJECTIVES: Demonstrating that Smad3 may play certain roles in cisplatin nephropathy due to its potential effect on programmed cell death and inflammation. METHODS: Here, we established a cisplatin-induced AKI mouse model with Smad3 knockout mice and created stable in vitro models with Smad3 knockdown tubular epithelial cells. In addition, we tested the potential of Smad3-targeted therapy using 2 in vivo protocols - lentivirus-mediated Smad3 silencing in vivo and use of naringenin, a monomer used in traditional Chinese medicine and a natural inhibitor of Smad3. RESULTS: Disruption of Smad3 attenuated cisplatin-induced kidney injury, inflammation, and NADPH oxidase 4-dependent oxidative stress. We found that Smad3-targeted therapy protected against loss of renal function and alleviated apoptosis, RIPK-mediated necroptosis, renal inflammation, and oxidative stress in cisplatin nephropathy. CONCLUSIONS: These findings show that Smad3 promotes cisplatin-induced AKI and Smad3-targeted therapy protects against this pathological process. These findings have substantial clinical relevance, as they suggest a therapeutic target for AKI.

AANG: A natural compound formula for overcoming multidrug resistance via synergistic rebalancing the TGF-ß/Smad signalling in hepatocellular carcinoma.

Cancer cells are high in heterogeneity and versatility, which can easily adapt to the external stresses via both primary and secondary resistance. Targeting of tumour microenvironment (TME) is a new approach and an ideal therapeutic strategy especially for the multidrug resistant cancer. Recently, we invented AANG, a natural compound formula containing traditional Chinese medicine (TCM) derived Smad3 inhibitor Naringenin (NG) and Smad7 activator Asiatic Acid (AA), for rebalancing TGF-ß/Smad signalling in the TME, and its implication on the multidrug resistance is still unexplored. Here, we observed that an equilibrium shift of the Smad signalling in patients with hepatocellular carcinoma (HCC), which was dramatically enhanced in the recurrent cases showing p-glycoprotein overexpression. We optimized the formula ratio and dosage of AANG that effectively inhibit the proliferation of our unique human multidrug resistant subclone R-HepG2. Mechanistically, we found that AANG not only inhibits Smad3 at post-transcriptional level, but also upregulates Smad7 at transcriptional level in a synergistic manner in vitro. More importantly, AANG markedly suppressed the growth and p-glycoprotein expression of R-HepG2 xenografts in vivo. Thus, AANG may represent a novel and safe TCM-derived natural compound formula for overcoming HCC with p-glycoprotein-mediated multidrug resistance.

Quercetin protects against cisplatin-induced acute kidney injury by inhibiting Mincle/Syk/NF-κB signaling maintained macrophage inflammation.

Acute kidney injury (AKI) with high incidence and mortality is the main cause of chronic kidney disease. Previous studies have indicated that quercetin, an abundant flavonoid in plants, exhibited renoprotective role in AKI. However, the underlying mechanism is largely unknown. In this study, we try to explore whether quercetin protects against AKI by inhibiting macrophage inflammation via regulation of Mincle/Syk/NF-κB signaling. The results demonstrated that quercetin can significantly inhibit expression and secretion of IL-1ß, IL-6, and TNF-α in LPS-induced bone marrow-derived macrophages (BMDMs) and reduce activity of Mincle/Syk/NF-κB signaling in vitro. We also found that quercetin can strongly reduce the concentration of serum creatinine, BUN, IL-1ß, IL-6, and TNF-α in cisplatin-induced AKI model. Furthermore, quercetin down-regulated protein levels of Mincle, phosphorylated Syk and NF-κB in kidney macrophages of AKI, as well as inhibited M1, up-regulated M2 macrophage activity. Notably, the down-regulation of LPS-induced inflammation by quercetin was reversed after adding TDB (an agonist of Mincle) in BMDMs, suggesting that quercetin suppresses macrophage inflammation may mainly through inhibiting Mincle and its downstream signaling. In summary, these findings clarified a new mechanism of quercetin improving AKI-induced kidney inflammation and injury, which provides a new drug option for the clinical treatment of AKI.

Curcumin relieved cisplatin-induced kidney inflammation through inhibiting Mincle-maintained M1 macrophage phenotype.

BACKGROUND: Acute kidney injury (AKI) is a common kidney disease with a high risk of death and can develop into chronic kidney disease (CKD) and renal failure eventually. Curcumin, an herbal supplement, has been reported exhibiting a renoprotective role in AKI. However, the underlying mechanism is largely unclear. PURPOSE: Recent research showed that Mincle (Macrophage-inducible C-type lectin) maintained M1 macrophage polarization, which plays a key role in kidney injury of AKI through up-regulating the expression and secretion of inflammatory cytokines. Here, we investigated the effects of Curcumin on Mincle expression and macrophage polarization in vitro using lipopolysaccharide (LPS) induced macrophage inflammatory cell model and in vivo using a cisplatin induced murine AKI (cis-AKI) model. METHODS: Cell activation, inflammatory cytokines expression and secretion, protein levels, macrophage polarization and renal pathology were analyzed. RESULTS: Our results showed that Curcumin markedly reduced the mRNA expression and secretion of IL-1ß, IL-6, TNFα and MCP-1 in LPS stimulated RAW264.7 cell and the supernatant. The same results were found in Curcumin treated cis-AKI kidney and blood. The data also demonstrated that Curcumin remarkably down-regulated mRNA expression and protein level of Mincle in cis-AKI kidney and also reduced expression of iNOS (M1 macrophage marker) as well as inhibited the activation of Syk and NF-kB. Interestingly, although Mincle deletion in RAW264.7 cell largely decreased the LPS-induced protein level of iNOS, Curcumin cannot further reduce expression of iNOS without Mincle, indicating that Curcumin inhibits M1 macrophage with a Mincle-dependent pattern. Furthermore, flow cytometry results showed that Curcumin significantly decreased the iNOS positive macrophages and increased the CD206 (M2 macrophage marker) positive macrophages in vivo and in vitro. CONCLUSION: Our findings prove that Curcumin protects kidney from cisplatin induced AKI through inhibiting Mincle maintained M1 macrophage phenotype, that may provide a specific renoprotection mechanism for Curcumin to develop it as a new therapeutic candidate for AKI.

The preventive and therapeutic implication for renal fibrosis by targetting TGF-ß/Smad3 signaling.

It is well established that Smad3 is a key downstream effector of transforming growth factor-ß (TGF-ß) signaling in tissue fibrogenesis. We reported here that targetting Smad3 specifically with a Smad3 inhibitor SIS3 is able to prevent or halt the progression of renal fibrosis in a mouse model of unilateral ureteral obstructive nephropathy (UUO). We found that preventive treatment with SIS3 at the time of disease induction largely suppressed progressive renal fibrosis by inhibiting α-smooth muscle actin (α-SMA) + myofibroblast accumulation and extracellular matrix (collagen I (Col.I) and fibronectin (FN)) production. Importantly, we also found that treatment with SIS3 on established mouse model of UUO from day 4 after UUO nephropathy halted the progression of renal fibrosis. Mechanistically, the preventive and therapeutic effects of SIS3 on renal fibrosis were associated with the inactivation of Smad3 signaling and inhibition of TGF-ß1 expression in the UUO kidney. In conclusion, results from the present study suggest that targetting Smad3 may be a specific and effective therapy for renal fibrosis.

Therapeutic Effects of Tangshen Formula on Diabetic Nephropathy in Rats.

OBJECTIVE: Inflammation and fibrosis are essential promoters in the pathogenesis of diabetic nephropathy (DN) in type 2 diabetes. The present study examined the anti-inflammation and anti-fibrosis effect of Tangshen Formula (TSF), a traditional Chinese medicine, on DN. RESEARCH DESIGN AND METHODS: Protective role of TSF in DN was examined in a rat model of type 2 DN that was established by high-fat diet-fed and low-dose-streptozotocin injection. TSF was suspended in 0.5% CMC-Na solution and delivered by oral gavage at a dosage of 1.67g/Kg body weight/day. The therapeutic effects and mechanisms of TSF on diabetic kidney injury were examined. RESULTS: We found that TSF treatment for 20 weeks attenuated DN by significantly inhibiting urinary excretion of albumin and renal histological injuries. These beneficial effects were associated with an inactivation of NF-κB signaling, thereby blocking the upregulation of pro-inflammatory cytokines (IL-1ß, TNFα), chemokine (MCP-1), and macrophage infiltration in the TSF-treated rats with type 2 DN. In addition, TSF treatment also inactivated TGF-ß/Smad3 signaling and therefore suppressed renal fibrosis including expressions of fibronectin, collagen I, and collagen IV. Further studies revealed that the inhibitory effect of TSF on TGF-ß/Smad3 and NF-κB signaling in DN was associated with inhibition of Smurf2-dependent ubiquitin degradation of Smad7. CONCLUSIONS: The present study reveals that TSF has therapeutic potential for type 2 DN in rats. Blockade of NF-κB-driven renal inflammation and TGF-ß/Smad3-mediated renal fibrosis by preventing the Smurf2-mediated Smad7 degradation pathway may be mechanisms through which TSF inhibits type 2 DN.

Treatment of renal fibrosis by rebalancing TGF-ß/Smad signaling with the combination of asiatic acid and naringenin.

We recently showed that imbalance of TGF-ß/Smad signaling with over-activation of Smad3 but lower levels of Smad7 is a central mechanism of tissue fibrosis. In the present study, we report here that inhibition of Smad3 with naringenin (NG) and upregulation of Smad7 with asiatic acid (AA) produced an additive effect on inhibition of renal fibrosis in a mouse model of obstructive nephropathy. We found that AA, a triterpene from Centella Asiatica, functioned as a Smad7 agonist and suppressed TGF-ß/Smad3-mediated renal fibrosis by inducing Smad7. Whereas, NG, a flavonoid from grapefruits and citrus fruits, was a Smad3 inhibitor that inhibited renal fibrosis by blocking Smad3 phosphorylation and transcription. The combination of AA and NG produced an additive effect on inhibition of renal fibrosis by blocking Smad3 while upregulating Smad7. Thus, rebalancing the disorder of TGF-ß/Smad signaling by treatment with AA and NG may represent as a novel and effective therapy for chronic kidney disease associated with fibrosis.

Renoprotective effect of berberine on type 2 diabetic nephropathy in rats.

Inflammation, fibrosis, and lipid disorder are essential promoters in the pathogenesis of diabetic kidney injury in diabetes mellitus type 2. Berberine (BBR) has been reported to have beneficial effects on diabetic nephropathy, but its action mechanism is still unclear. The present study was designed to elucidate the therapeutic mechanism of BBR in a type 2 diabetic nephropathy rat model induced by a high-fat diet and low-dose streptozotocin injection. The diabetic rats were treated with or without BBR by gavage for 20 weeks and examined by serology, 24-h albuminuria, histology, immunohistochemistry, and molecular analyses. Results showed that treatment with BBR significantly reduced serum levels of blood glucose and lipids, inhibited urinary excretion of albumin, and attenuated renal histological injuries in diabetic rats. Berberine treatment also inhibited renal inflammation, which was associated with inactivation of nuclear factor kappa-light-chain-enhancer of activated B-cell signalling. As a result, the upregulation of pro-inflammatory cytokines (interleukin-1ß, tumour necrosis factor-α) and chemokine (monocyte chemotactic protein-1) was blocked. In addition, BBR treatment also inactivated transforming growth factor-ß/Smad3 signalling and suppressed renal fibrosis, including expression of fibronectin, collagen I, and collagen IV. The present study reveals that BBR is a therapeutic agent for attenuating type 2 diabetic nephropathy by inhibiting nuclear factor kappa-light-chain-enhancer of activated B cell-driven renal inflammation and transforming growth factor-ß/Smad3 signalling pathway.

Smad7 protects against chronic aristolochic acid nephropathy in mice.

Chronic Aristolochic Acid Nephropathy (AAN) is a progressive chronic kidney disease related to herb medicine. However, treatment for chronic AAN remains ineffective. We report here that Smad7 is protective and has therapeutic potential for chronic AAN. In a mouse model of chronic AAN, progressive renal injury was associated with a loss of renal Smad7 and disruption of Smad7 largely aggravated the severity of chronic AAN as demonstrated by a significant increase in levels of 24-hour urinary protein excretion, serum creatinine, and progressive renal fibrosis and inflammation. In contrast, restored Smad7 locally in the kidneys of Smad7 knockout mice prevented the progression of chronic AAN. Further studies revealed that worsen chronic AAN in Smad7 knockout mice was associated with enhanced activation of TGF-ß/Smad3 and NF-κB signaling pathways, which was reversed when renal Smad7 was restored. Importantly, we also found that overexpression of Smad7 locally in the kidneys with established chronic AAN was capable of attenuating progressive chronic AAN by inactivating TGF-ß/Smad3-medated renal fibrosis and NF-κB-driven renal inflammation. In conclusion, Smad7 plays a protective role in the pathogenesis of chronic AAN and overexpression of Smad7 may represent a novel therapeutic potential for chronic AAN.

Metabolomic and lipidomic study of the protective effect of Chaihuang-Yishen formula on rats with diabetic nephropathy.

ETHNOPHARMACOLOGICAL RELEVANCE: Chaihuang-Yishen formula (CHYS) is a Chinese herbal formula that has been shown clinically to effectively treat chronic kidney disease including diabetic nephropathy (DN), also known as diabetic kidney disease. Our previous animal studies showed that numerous intrarenal metabolites were associated with the development of DN. In the present work, an integrated metabolomic and lipidomic analysis was used to further examine whether CHYS could attenuate the development of DN by regulating the disordered metabolic pathways. METHOD: Progressive diabetic kidney disease was induced in Wistar rats by uninephrectomy and a single intraperitoneal injection of streptozocin. Over 20 weeks, one group of animals was treated with CHYS and another group went untreated. Effects of CHYS on metabolomic and lipidomic changes in the renal cortex of diabetic rats were studied using gas chromatography/time-of-flight mass spectrometry, ultra-performance liquid chromatography/time-of-flight mass spectrometry, and tandem MS-based metabolomic and lipidomic. The well-established drug fosinopril was used as positive control throughout the experiment. RESULTS: Like fosinopril, treatment with CHYS produced a renoprotective effect against DN. Metabolomic and lipidomic analyses showed that the therapeutic effect of CHYS on DN was significantly associated with inhibition of the elevated organic toxins including several uremic toxins and glucuronides, and normalization of diminished phospholipids, especially sphingomyelins. CONCLUSION: Improved abnormal metabolic and lipidomic disorders, such as accumulation of uremic toxins and glucuronides and phospholipids, may be mechanisms by which treatment of CHYS inhibits DN. Results from this study provide new evidence for the pharmacologic characteristics of CHYS on DN.

Chaihuang-Yishen granule inhibits diabetic kidney disease in rats through blocking TGF-ß/Smad3 signaling.

OBJECTIVE: Increasing evidence shows that TGF-ß1 is a key mediator in diabetic nephropathy (DN) and induces renal fibrosis positively by Smad3 but negatively by Smad7. However, treatment of DN by blocking the TGF-ß/Smad pathway remains limited. The present study investigated the anti-fibrotic effect of a traditional Chinese medicine, Chaihuang-Yishen granule (CHYS), on DN. RESEARCH DESIGN AND METHODS: Protective role of CHYS in DN was examined in an accelerated type 1 DN induced by streptozotocin in uninephrectomized Wistar rats. CHYS, at a dose of 0.56 g/kg body weight, was administered by a daily gastric gavage for 20 weeks and the therapeutic effect and potential mechanisms of CHYS on diabetic kidney injury were examined. RESULTS: Treatment with CHYS attenuated diabetic kidney injury by significantly inhibiting 24-h proteinuria and progressive renal fibrosis including glomerulosclerotic index, tubulointerstitial fibrosis index, and upregulation of extracellular matrix (collagen I, IV, and fibronectin), despite the same levels of blood glucose. Further studies revealed that inhibition of renal fibrosis in CHYS-treated diabetic rats was associated with inhibition of TGF-ß1/Smad3 signaling as demonstrated by upregulation of Smad7 but downregulation of TGF-ß1, TGF-ß receptors, activation of Smad3, and expression of miRNA-21. CONCLUSIONS: CHYS may be a therapeutic agent for DN. CHYS attenuates DN by blocking TGF-ß/Smad3-mediated renal fibrosis.

Mechanism of chronic aristolochic acid nephropathy: role of Smad3.

Aristolochic acid nephropathy (AAN) has become a worldwide disease and is the most severe complication related to the use of traditional Chinese medicine. However, the pathogenic mechanisms of AAN remain unclear and therapies are limited. The present study tested the hypothesis that transforming growth factor (TGF)-beta/Smad3 may be a key pathway leading to chronic AAN. This was examined in vivo in Smad3 wild-type/knockout (WT/KO) mice and in vitro in tubular epithelial cells with knockdown of Smad2 or Smad3. Results revealed that chronic administration of aristolochic acid (AA) resulted in a severe AAN characterized by progressive renal dysfunction and tubulointerstitial fibrosis including epithelial-mesenchymal transition (EMT) in Smad3 WT mice, but not in Smad3 KO mice, suggesting a critical role for Smad3 in the development of AAN. This was further tested in vitro. We found that AA was able to activate Smad signaling to mediate EMT and renal fibrosis via both TGF-beta-dependent and JNK/MAP kinase-dependent mechanisms because blockade of JNK and specific knockdown of Smad3, but not Smad2, were able to attenuate AA-stimulated collagen matrix expression and EMT. In conclusion, TGF-beta/Smad3 may be an essential mediator for chronic AAN. Results from this study indicate that specific blockade of the TGF-beta/Smad3 signaling pathway may have therapeutic potential for chronic AAN.

Bradykinin and high glucose promote renal tubular inflammation.

BACKGROUND: The role of the kallikrein-kinin system in diabetic nephropathy remains controversial. METHODS AND RESULTS: High-glucose (HG) super-induced interleukin (IL)-6, CCL-2, transforming growth factor (TGF)-beta, vascular endothelial growth factor (VEGF) and B(2)K receptor (B(2)KR) mRNA in cultured proximal tubular epithelial cells (PTEC), whereas bradykinin (BK) upregulated IL-6, CCL-2 and TGF-beta mRNA. HG activated mitogen-activated protein kinase (MAPK) p42/p44 and protein kinase C (PKC) signals, whereas BK only activated MAPK. Tubular expression of these mediators and tissue kallikrein 1 (KLK1) was confirmed in human diabetic kidney biopsies. Inhibition of MAPK p42/p44 by PD98059 partially reduced HG and BK induction of IL-6, CCL-2 and TGF-beta, whereas inhibition of PKC by staurosporine partially reduced HG- but not BK-induced overexpression of these cytokines and that of VEGF. Staurosporine and PD98059 synergistically reduced the effect of HG on IL-6, CCL-2 and TGF-beta expression. The B(2)KR blocker, icatibant, downregulated BK- and HG-induced MAPK p42/p44 but not HG-induced PKC activation and partially reduced both HG- and BK-induced IL-6, CCL-2 and TGF-beta secretion. HG stimulated expression of KLK1 and low-molecular-weight kininogen (LMWK) and its downstream effects were attenuated by aprotinin (tissue kallikrein inhibitor). The peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist, rosiglitazone, attenuated HG-induced PKC but not HG- or BK- induced MAPK p42/44 activation and reduced HG-stimulated VEGF, along with IL-6, CCL-2 and TGF-beta secretion. Rosiglitazone plus icatibant further reduced these effects of HG. CONCLUSIONS: In conclusion, HG stimulates tubular proinflammatory, profibrotic and angiogenic signals, which is partly mediated through BK via MAPK signalling and partly through PKC independent of BK. The potential therapeutic role of complementary B(2)KR blockade and PPAR-gamma activation deserves clinical investigation.