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.

Effects of uric acid-lowering therapy (ULT) on renal outcomes in CKD patients with asymptomatic hyperuricemia: a systematic review and meta-analysis.

BACKGROUND: It is well known that asymptomatic hyperuricemia and gout play an important role in patients with chronic kidney disease (CKD). However, the effect of uric acid-lowering therapy (ULT) on the prognosis of CKD patients with asymptomatic hyperuricemia remains controversial. Therefore, we aim to investigate the influence of ULT on renal outcomes in these patients. METHODS: Comprehensive searches were conducted in PubMed, EMBASE, China National Knowledge Internet (CNKI), and the Cochrane Library, up until January 2024. We included randomized controlled trials (RCTs) that evaluated the effects of ULT on renal outcomes in CKD patients with asymptomatic hyperuricemia. RESULTS: A total of 17 studies were included in the meta-analysis. Compared with placebo or no treatment, ULT preserved the loss of estimated glomerular filtrating rate (eGFR) (Weighted mean difference [WMD] and its 95% confidence intercal(CI): 2.07 [0.15,3.98] mL/min/1.73m2) at long-term subgroup. At the same time, short-term subgroup also proved the preserved loss of eGFR (WMD 5.74[2.09, 9.39] mL/min/1.73m2). Compared with placebo or no treatment, ULT also reduced the increase in serum creatinine (Scr) at short-term (WMD -44.48[-84.03,-4.92]µmol/L) subgroup and long-term (WMD -46.13[-65.64,-26.62]µmol/L) subgroup. ULT was associated with lower incidence of the events of doubling of Scr without dialysis (relative risk (RR) 0.32 [0.21, 0.49], p < 0.001). However, no difference was found for lower incidence of acute kidney injury (AKI) (p = 0.943). CONCLUSIONS: According to our study, ULT is beneficial for slowing CKD progression both in short to long-term follow-ups. Additionally, in patients younger than 60 years old, the protective effect of ULT on renal outcome is more pronounced. However, it showed no significant difference in the incidence of AKI. These findings underscore the importance of considering ULT in clinical strategies for CKD patients with asymptomatic hyperuricemia.

P2Y12 inhibitor clopidogrel inhibits renal fibrosis by blocking macrophage-to-myofibroblast transition.

Clopidogrel, a P2Y12 inhibitor, is a novel anti-fibrosis agent for chronic kidney disease (CKD), but its mechanisms remain unclear, which we investigated by silencing P2Y12 or treating unilateral ureteral obstruction (UUO) in LysM-Cre/Rosa Tomato mice with clopidogrel in vivo and in vitro. We found that P2Y12 was significantly increased and correlated with progressive renal fibrosis in CKD patients and UUO mice. Phenotypically, up to 82% of P2Y12-expressing cells within the fibrosing kidney were of macrophage origin, identified by co-expressing CD68/F4/80 antigens or a macrophage-lineage-tracing marker Tomato. Unexpectedly, more than 90% of P2Y12-expressing macrophages were undergoing macrophage-to-myofibroblast transition (MMT) by co-expressing alpha smooth muscle actin (α-SMA), which was also confirmed by single-cell RNA sequencing. Functionally, clopidogrel improved the decline rate of the estimated glomerular filtration rate (eGFR) in patients with CKD and significantly inhibited renal fibrosis in UUO mice. Mechanistically, P2Y12 expression was induced by transforming growth factor ß1 (TGF-ß1) and promoted MMT via the Smad3-dependent mechanism. Thus, silencing or pharmacological inhibition of P2Y12 was capable of inhibiting TGF-ß/Smad3-mediated MMT and progressive renal fibrosis in vivo and in vitro. In conclusion, P2Y12 is highly expressed by macrophages in fibrosing kidneys and mediates renal fibrosis by promoting MMT via TGF-ß/Smad3 signaling. Thus, P2Y12 inhibitor maybe a novel and effective anti-fibrosis agent for CKD.

Neuropeptide Y attenuates cardiac remodeling and deterioration of function following myocardial infarction.

Plasma levels of neuropeptide Y (NPY) are elevated in patients with acute myocardial infarction (AMI), but its role in AMI remains unclear, which was examined here in NPY wild-type/knockout (WT/KO) mice treated with/without exogenous NPY and its Y1 receptor antagonist (Y1Ra) BIBP 3226. We found that AMI mice lacking NPY developed more severe AMI than WT mice with worse cardiac dysfunction, progressive cardiac inflammation and fibrosis, and excessive apoptosis but impairing angiogenesis. All of these changes were reversed when the NPY KO mice were treated with exogenous NPY in a dose-dependent manner. Interestingly, treatment with NPY also dose dependently attenuated AMI in WT mice, which was blocked by BIBP 3226. Phenotypically, cardiac NPY was de novo expressed by infiltrating macrophages during the repairing or fibrosing process in heart-failure patients and AMI mice. Mechanistically, NPY was induced by transforming growth factor (TGF)-ß1 in bone marrow-derived macrophages and signaled through its Y1R to exert its pathophysiological activities by inhibiting p38/nuclear factor κB (NF-κB)-mediated M1 macrophage activation while promoting the reparative M2 phenotype in vivo and in vitro. In conclusion, NPY can attenuate AMI in mice. Inhibition of cardiac inflammation and fibrosis while enhancing angiogenesis but reducing apoptosis may be the underlying mechanisms through which NPY attenuates cardiac remodeling and deterioration of function following AMI.

New COL4A5 mutation in IgA nephropathy.

PURPOSE: IgA nephropathy (IgAN) is the most common type of primary glomerulonephritis and a leading cause of chronic kidney disease (CKD) and end-stage kidney disease (ESKD). Recently, some case reports have shown that COL4A5 mutation is associated with IgAN. Here, we identified a new COL4A5 gene mutation in IgAN in a Chinese family. MATERIALS AND METHODS: In the present study, the proband and his 23-year-old younger brother were both diagnosed with IgAN, manifested as haematuria, proteinuria and chronic kidney injury without hearing loss or ocular symptoms. Additionally, the proband's 30-year-old younger brother, also diagnosed with ESKD, had been undergoing dialysis for 2 years with normal hearing and eyesight. To exclude genetic disease, we conducted whole-exome sequencing and Sanger sequencing assays. RESULTS: We found a new mutation in the COL4A5 gene (chrX:107 814 698, c.438+2->AAACCAATTATA-), a novel insertion mutation. Using vector transcription and Minigene transcriptional analyses, we verified, for the first time, the novel mutation pathogenicity of the COL4A5 gene. CONCLUSION: Together with other published data, we suggest that genetic screening should be performed in IgAN, particularly for patients with a familial history. The effects of different mutated splice sites of the COL4A5 gene, as well as the tissue specificity of the splicing machinery contributing to the pathogenesis and prognosis of IgAN, remains unclear and warrants further exploration in the future.

Systematic review and subgroup analysis of the incidence of acute kidney injury (AKI) in patients with COVID-19.

BACKGROUND: Acute kidney injury (AKI) occurs among patients with coronavirus disease-19 (COVID-19) and has also been indicated to be associated with in-hospital mortality. Remdesivir has been authorized for the treatment of COVID-19. We conducted a systematic review to evaluate the incidence of AKI in hospitalized COVID-19 patients. The incidence of AKI in different subgroups was also investigated. METHODS: A thorough search was performed to find relevant studies in PubMed, Web of Science, medRxiv and EMBASE from 1 Jan 2020 until 1 June 2020. The systematic review was performed using the meta package in R (4.0.1). RESULTS: A total of 16,199 COVID-19 patients were included in our systematic review. The pooled estimated incidence of AKI in all hospitalized COVID-19 patients was 10.0% (95% CI: 7.0-12.0%). The pooled estimated proportion of COVID-19 patients who needed continuous renal replacement therapy (CRRT) was 4% (95% CI: 3-6%). According to our subgroup analysis, the incidence of AKI could be associated with age, disease severity and ethnicity. The incidence of AKI in hospitalized COVID-19 patients being treated with remdesivir was 7% (95% CI: 3-13%) in a total of 5 studies. CONCLUSION: We found that AKI was not rare in hospitalized COVID-19 patients. The incidence of AKI could be associated with age, disease severity and ethnicity. Remdesivir probably did not induce AKI in COVID-19 patients. Our systematic review provides evidence that AKI might be closely associated with SARS-CoV-2 infection, which should be investigated in future studies.

miR-20a-5p is enriched in hypoxia-derived tubular exosomes and protects against acute tubular injury.

Exosomes have been shown to effectively regulate the biological functions of target cells. Here, we investigated the protective effect and mechanism of hypoxia-induced renal tubular epithelial cells (TECs)-derived exosomes on acute tubular injury. We found that in vitro hypoxia-induced tubular exosomes (Hy-EXOs) were protective in acute tubular injury by promoting TECs proliferation and improving mitochondrial functions. By using exosome miRNA sequencing, we identified miR-20a-5p was abundant and was a key mechanism for the protective effect of Hy-EXOs on tubular injury as up-regulation of miR-20a-5p enhanced but down-regulation of miR-20a-5p inhibited the protective effect of Hy-EXOs on tubular injury under hypoxia conditions. Further study in a mouse model of ischemia-reperfusion-induced acute kidney injury (IRI-AKI) also confirmed this notion as pre-treating mice with the miR-20a-5p agomir 48 h prior to AKI induction was capable of inhibiting IRI-AKI by lowering serum levels of creatinine and urea nitrogen, and attenuating the severity of tubular necrosis, F4/80(+) macrophages infiltration and vascular rarefaction. Mechanistically, the protective effect of miR-20a-5p on acute kidney injury (AKI) was associated with inhibition of TECs mitochondrial injury and apoptosis in vitro and in vivo. In conclusion, miR-20a-5p is enriched in hypoxia-derived tubular exosomes and protects against acute tubular injury. Results from the present study also reveal that miR-20a-5p may represent as a novel therapy for AKI.

CD8+CD103+ iTregs Inhibit Chronic Graft-versus-Host Disease with Lupus Nephritis by the Increased Expression of CD39.

Many patients with systemic lupus erythematosus (SLE) have lupus nephritis, one of the severe complications of SLE. We previously reported that CD8+CD103+ T regulatory cells induced ex vivo with transforming growth factor ß (TGF-ß) (iTregs) inhibited immune cells responses to ameliorate excessive autoimmune inflammation. However, the molecular mechanism(s) underlying the role of these CD8+ iTregs is still unclear. Here we identified that CD39, which is highly expressed on CD8+ iTregs, crucially contributes to the immunosuppressive role of the CD8+CD103+ iTregs. We showed that adoptive transfer of CD8+CD103+ iTregs significantly relieves the chronic graft-versus-host disease with lupus nephritis and CD39 inhibitor mostly abolished the functional activities of these CD8+ iTregs in vitro and in vivo. CD39+ cells sorted from CD8+CD103+ iTregs were more effective in treating lupus nephritis than CD39- partner cells in vivo. Furthermore, human CD8+ iTregs displayed increased CD103 and CD39 expressions, and CD39 was involved in the suppressive function of human CD8+ iTregs. Thus, our data implicated a crucial role of CD39 in CD8+CD103+ iTregs in treating lupus nephritis, and CD39 could be a new phenotypic biomarker for the identification of highly qualified CD8+ Tregs. This subpopulation may have therapeutic potential in patients with SLE nephritis and other autoimmune diseases.

The incidence, risk factors, and long-term outcomes of acute kidney injury in hospitalized diabetic ketoacidosis patients.

BACKGROUND: Emerging evidence has demonstrated that acute kidney injury (AKI) is an important risk factor associated with increased morbidity and mortality in diabetic ketoacidosis (DKA) patients. The current study aimed to investigate the incidence rate, risk factors, long-term renal outcomes, and mortality in DKA patients with AKI. METHODS: A total of 179 patients diagnosed with DKA at Sun Yat-sen Memorial Hospital from January 2012 to January 2018 were included in the analysis. AKI was diagnosed according to the 2012 KDIGO criteria. Risk factors, long-term renal outcomes, and mortality were analyzed by logistic regression and Cox proportional hazards models. RESULTS: Among 179 DKA patients, 98 patients (54.75%) were diagnosed as AKI. Aging; increased blood glucose, serum uric acid and white blood cells; decreased serum pH and albumin; coma; and preexisting chronic kidney disease (CKD) were risk factors of AKI in patients with DKA. During follow-up, DKA patients with AKI showed more than a two-fold decline in eGFR within 1 year after discharge from the hospital when compared with non-AKI DKA patients. Furthermore, AKI was also an independent risk factor for poor long-term renal outcomes and mortality in DKA patients. CONCLUSIONS: Multiple risk factors contribute to the development of AKI in DKA patients. AKI and advanced AKI stage are associated with rapid progressive CKD and long-term mortality in patients with DKA.

Systemic inflammation modulates the ability of serum ferritin to predict all-cause and cardiovascular mortality in peritoneal dialysis patients.

BACKGROUND: This study aimed to ascertain whether the correlation of high serum ferritin with mortality is affected by systemic inflammation and to investigate the optimal serum ferritin level for predicting death when inflammation is considered in peritoneal dialysis (PD) patients. METHODS: We classified 221 patients into four groups according to serum ferritin concentration (100 µg/L) and high-sensitivity CRP (hs-CRP) level (3 mg/L), and followed them regularly from the date of catheterization to Dec 31, 2016, at Sun Yat-Sen Memorial Hospital, China. Clinical and biochemical data were collected at baseline, and clinical outcomes such as all-cause and cardiovascular mortality were assessed. RESULTS: During a median follow-up of 35 months (3 ~ 109 months), 50 (22.6%) deaths occurred. Cardiovascular disease (46.0%) was the most common cause of death, followed by infection (10.0%). The Kaplan-Meier survival analysis and log-rank test revealed significantly worse survival accumulation among PD patients with higher serum ferritin (≥100 µg/L) under elevated hsCRP levels (> 3 mg/L) (P = 0.022). A multivariate Cox regression analysis revealed that an increased serum ferritin level was independently associated with a higher risk of all-cause and cardiovascular mortality in PD patients (HR = 3.114, P = 0.021; and HR = 9.382, P = 0.032) with hsCRP above 3 mg/L after adjusting for relevant confounding factors. CONCLUSION: Higher serum ferritin levels were associated with an increased risk of all-cause and cardiovascular mortality in patients undergoing PD only in the presence of elevated hsCRP levels. The correlation of serum ferritin with poor outcome should take into consideration systemic inflammation.

The baseline levels and risk factors for high-sensitive C-reactive protein in Chinese healthy population.

BACKGROUND: Recent studies show that C-reactive protein (CRP) is not only a biomarker but also a pathogenic mediator contributing to the development of inflammation and ageing-related diseases. However, serum levels of CRP in the healthy ageing population remained unclear, which was investigated in the present study. METHODS: Serum levels of high sensitive C-reactive protein (hs-CRP), glucose (Glu), triglyceride (TG), cholesterol (CHOL), high-density lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), superoxide dismutase (SOD), serum creatinine (SCr), serum uric acid (SUA) were measured in 6060healthy subjects (3672 male and 2388 female, mean age:45.9 years) who received routine physical examination at Sun Yat-sen Memorial Hospital, Guangzhou, China. RESULTS: In total of 6060 healthy people, serum levels of hs-CRP were significantly increased with ageing (P < 0.05), particularly in those with age over 45-year-old (1.31[0.69-2.75] vs 1.05[0.53-2.16]mg/L, P < 0.001). Interestingly, levels of serum hs-CRP were significantly higher in male than female population (1.24[0.65-2.57] vs 1.07[0.53-2.29]mg/L, P < 0.001). Correlation analysis also revealed that serum levels of hs-CRP positively correlated with age and SUA, but inversely correlated with serum levels of HDL-c and SOD (all P < 0.05). CONCLUSIONS: Baseline levels of serum hs-CRP are increased with ageing and are significantly higher in male than female healthy population. In addition, elevated serum levels of hs-CRP are also associated with increased SUA but decreased HDL-c and SOD. Thus, serum levels of hs-CRP may be an indicator associated with ageing in healthy Chinese population.

Association of echocardiographic parameters with mortality in hospitalized patients with lupus nephritis.

AIM: Increasing evidence shows that the cardiac involvement attributes to the mortality of patients with lupus nephritis (LN) and echocardiography provides a valid measurement for cardiac disease. However, the association between echocardiographic parameters and mortality in LN patients without cardiac disease history remains unclear. The aim of this study was to explore the relationship between echocardiographic parameters and the mortality in hospitalized LN patients without cardiac disease history. METHODS: A total of 436 LN patients without cardiac disease history who underwent echocardiography at Sun Yat-sen Memorial Hospital, between 1 January 2000 and 31 December 2014, were enrolled into this study. The association between echocardiographic parameters and all-cause and cardiac mortality of LN patients was examined by the Cox proportional hazards model. RESULTS: In this cohort study, the median duration of follow-up was 18 months. Among 436 hospitalized LN patients, 88 patients (20.2%) died. Of them, 38 patients (43.2%) died of cardiac disease. Cardiac symptoms, high systolic blood pressure, high serum levels of C-reactive protein, low serum albumin, low estimated glomerular filtration rate (eGFR), and decreased left ventricular ejection fraction (LVEF) were found to be independently associated with increased all-cause mortality. Furthermore, the cardiac symptoms, low eGFR, increased left ventricular mass index (LVMI), and decreased LVEF were independently correlated with an increased cardiac mortality risk. CONCLUSIONS: Decreased LVEF was associated with increased all-cause and cardiac mortality and increased LVMI was an independent risk factor for cardiac mortality in hospitalized LN patients without cardiac disease history.

The incidence, risk factors and in-hospital mortality of acute kidney injury in patients after abdominal aortic aneurysm repair surgery.

BACKGROUND: Acute kidney injury (AKI) is a severe complication associated with abdominal aortic aneurysm (AAA) repair. In this study, we evaluated the incidence, risk factors and in-hospital mortality of AKI in patients after the AAA repair surgery. METHODS: A total of 314 Chinese AAA patients who underwent endovascular aneurysm repair (EVAR) or open aneurysm repair (OPEN) were enrolled in this study. AKI was diagnosed according to the 2012 KDIGO criteria. Logistic regression modeling was used to explore risk factors of AKI, while risk factors associated with in-hospital mortality in AKI patients were investigated using Cox proportional hazards model and Kaplan-Meier analysis, respectively. Multicollinearity analysis was performed to identify the collinearity between the variables before logistic regression analysis and Cox proportional hazards analysis. RESULTS: Among 314 patients, 94 (29.9%) developed AKI after AAA repair surgery. Severity of AKI and ruptured AAA were independently associated with an increase in in-hospital mortality in AKI patients after AAA repair. Kaplan-Meier analysis identified severity of AKI as being negatively associated with hospital survival in AKI patients. Risk factors associated with AKI included cardiovascular disease (OR 3.169, 95% confidence interval (CI) 1.538 to 6.527, P = 0.002), decreased eGFR (OR 0.965, 95%CI 0.954 to 0.977, P < 0.001), ruptured AAA (OR 2.717, 95%CI 1.320 to 5.592, P = 0.007), renal artery involvement (OR 2.903, 95%CI 1.219 to 6.912, P = 0.016) and OPEN (OR 2.094, 95%CI 1.048 to 4.183, P = 0.036). Further subgroup analysis identified OPEN as an important risk factor of AKI in ruptured AAA patients but not in ruptured AAA patients. The incidence of AKI was significantly lower in EVAR than in OPEN (27.1% vs. 42.8%) and, similarly lower in nonruptured AAA than in ruptured AAA (26.2% vs. 48.1%). CONCLUSION: One-third of AAA patients developed AKI after repair surgery. Severity of AKI was associated with reduced survival rate in AAA patients who developed postoperative AKI. Decreased preoperative creatinine clearance, cardiovascular disease, ruptured AAA and OPEN were independent risk factors for postoperative AKI in all 314 AAA patients. Although a lower rate of incident AKI was observed in EVAR compared with OPEN, subgroup analysis of ruptured AAA versus nonruptured AAA showed that EVAR was an independent protective factor for AKI only in ruptured AAA patients but not in nonruptured AAA patients.

C-reactive protein promotes acute kidney injury by impairing G1/S-dependent tubular epithelium cell regeneration.

CRP (C-reactive protein) is regarded as an inflammatory biomarker in AKI (acute kidney injury), but its exact role in AKI remains unclear. Thus we sought to investigate the role of CRP in AKI. Clinically, elevated serum CRP levels were found to associate closely with increased serum creatinine and urea levels (P<0.01) in patients with AKI, which then fell after recovery from AKI. To determine the role of CRP in AKI, an ischaemia/reperfusion mouse model of AKI was developed using Tg (transgenic) mice that express human CRP. Compared with the WT (wild-type) mice, CRP Tg mice developed more severe renal injury at 24 h after ischaemia as determined by significantly increased serum creatinine and tubular necrosis. This was associated with an impaired TEC (tubular epithelium cell) regeneration as shown by an over 60% reduction in PCNA+ (proliferating-cell nuclear antigen) and BrdU+ (bromodeoxyuridine) TECs in CRP Tg mice with AKI. In vitro, the addition of CRP to a human TEC line (HK-2) also largely suppressed the proliferation of TECs. The functional role of CRP in AKI was demonstrated further by the blocking of CRP binding to the FcγRII (Fcγ receptor II) with a neutralizing anti-CD32 antibody, which restored TEC proliferation and prevented AKI in CRP Tg mice. Moreover, we found that impaired G1/S transition by suppression of the phosphorylation of CDK2 (cyclin-dependent kinase 2) and expression of cyclin E may be a key mechanism by which CRP inhibits TEC regeneration during the AKI repair process. In conclusion, CRP plays a pathogenic role in AKI by inhibiting G1/S-dependent TEC regeneration. The results of the present study suggest that targeting CRP signalling may offer a new therapeutic potential for AKI.

[Research advances on stem cell-based treatments in animal studies and clinical trials of lymphedema].

Objective: To summarize the progress of the roles and mechanisms of various types of stem cell-based treatments and their combination therapies in both animal studies and clinical trials of lymphedema. Methods: The literature on stem cell-based treatments for lymphedema in recent years at home and abroad was extensively reviewed, and the animal studies and clinical trials on different types of stem cells for lymphedema were summarized. Results: Various types of stem cells have shown certain effects in animal studies and clinical trials on the treatment of lymphedema, mainly through local differentiation into lymphoid endothelial cells and paracrine cytokines with different functions. Current research focuses on two cell types, adipose derived stem cells and bone marrow mesenchymal stem cells, both of which have their own advantages and disadvantages, mainly reflected in the therapeutic effect of stem cells, the difficulty of obtaining stem cells and the content in vivo. In addition, stem cells can also play a synergistic role in combination with other treatments, such as conservative treatment, surgical intervention, cytokines, biological scaffolds, and so on. However, it is still limited to the basic research stage, and only a small number of studies have completed clinical trials. Conclusion: Stem cells have great transformation potential in the treatment of lymphedema, but there is no unified standard in the selection of cell types, the amount of transplanted cells, and the timing of transplantation.

Role of C-Reactive Protein in Kidney Diseases.

Background: C-reactive protein (CRP) is an acute-phase protein and has been found to be a risk factor for acute kidney injury (AKI) and chronic kidney diseases (CKD). However, the role and mechanisms of CRP in AKI and CKD remain largely unclear. Summary: Clinically, elevated serum CRP is a risk factor or biomarker for patients with AKI and CKD. Interestingly, in critically ill COVID-19 patients, increased serum CRP is also associated with the development of AKI. Functionally, studies using human CRP transgenic mouse models find that CRP is pathogenic and can function as a mediator for AKI and CKD as mice overexpressing human CRP promote AKI and CKD. Mechanistically, CRP can promote AKI and CKD via NF-κB and Smad3-dependent mechanisms. We found that CRP can activate Smad3 signaling directly and cause AKI via the Smad3-p27-dependent G1 cell cycle arrest mechanism. Thus, targeting CRP-Smad3 signaling with a neutralizing antibody or Smad3 inhibitor can inhibit AKI. Key Messages: CRP acts not only as a biomarker but also as a mediator for AKI and CKD. CRP can activate Smad3 to induce cell death and cause progressive renal fibrosis. Thus, targeting CRP-Smad3 signaling may represent a promising therapy for AKI and CKD.

SARS-CoV-2 N protein induced acute kidney injury in diabetic db/db mice is associated with a Mincle-dependent M1 macrophage activation.

"Cytokine storm" is common in critically ill COVID-19 patients, however, mechanisms remain largely unknown. Here, we reported that overexpression of SARS-CoV-2 N protein in diabetic db/db mice significantly increased tubular death and the release of HMGB1, one of the damage-associated molecular patterns (DAMPs), to trigger M1 proinflammatory macrophage activation and production of IL-6, TNF-α, and MCP-1 via a Mincle-Syk/NF-κB-dependent mechanism. This was further confirmed in vitro that overexpression of SARS-CoV-2 N protein caused the release of HMGB1 from injured tubular cells under high AGE conditions, which resulted in M1 macrophage activation and production of proinflammatory cytokines via a Mincle-Syk/NF-κB-dependent mechanism. This was further evidenced by specifically silencing macrophage Mincle to block HMGB1-induced M1 macrophage activation and production of IL-6, TNF-α, and MCP-1 in vitro. Importantly, we also uncovered that treatment with quercetin largely improved SARS-CoV-2 N protein-induced AKI in db/db mice. Mechanistically, we found that quercetin treatment significantly inhibited the release of a DAMP molecule HMGB1 and inactivated M1 pro-inflammatory macrophage while promoting reparative M2 macrophage responses by suppressing Mincle-Syk/NF-κB signaling in vivo and in vitro. In conclusion, SARS-CoV-2 N protein-induced AKI in db/db mice is associated with Mincle-dependent M1 macrophage activation. Inhibition of this pathway may be a mechanism through which quercetin inhibits COVID-19-associated AKI.

Signaling mechanisms of SARS-CoV-2 Nucleocapsid protein in viral infection, cell death and inflammation.

COVID-19 which is caused by severe acute respiratory syndrome coronavirus (SARS-CoV-2) has posed a worldwide pandemic and a major global public health threat. SARS-CoV-2 Nucleocapsid (N) protein plays a critical role in multiple steps of the viral life cycle and participates in viral replication, transcription, and assembly. The primary roles of N protein are to assemble with genomic RNA into the viral RNA-protein (vRNP) complex and to localize to the replication transcription complexes (RTCs) to enhance viral replication and transcription. N protein can also undergo liquid-liquid phase separation (LLPS) with viral genome RNA and inhibit stress granules to facilitate viral replication and assembly. Besides the function in viral life cycle, N protein can bind GSDMD to antagonize pyroptosis but promotes cell death via the Smad3-dependent G1 cell cycle arrest mechanism. In innate immune system, N protein inhibits IFN-ß production and RNAi pathway for virus survival. However, it can induce expression of proinflammatory cytokines by activating NF-κB signaling and NLRP3 inflammasome, resulting in cytokine storms. In this review article, we are focusing on the signaling mechanisms of SARS-CoV-2 N protein in viral replication, cell death and inflammation.

SARS-CoV-2 N Protein Induces Acute Kidney Injury via Smad3-Dependent G1 Cell Cycle Arrest Mechanism.

COVID-19 is infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and can cause severe multiple organ injury and death. Kidney is one of major target organs of COVID-19 and acute kidney injury (AKI) is common in critically ill COVID-19 patients. However, mechanisms through which COVID-19 causes AKI remain largely unknown and treatment remains unspecific and ineffective. Here, the authors report that normal kidney-specifically overexpressing SARS-CoV-2 N develops AKI, which worsens in mice under ischemic condition. Mechanistically, it is uncovered that SARS-CoV-2 N-induced AKI is Smad3-dependent as SARS-CoV-2 N protein can interact with Smad3 and enhance TGF-ß/Smad3 signaling to cause tubular epithelial cell death and AKI via the G1 cell cycle arrest mechanism. This is further confirmed in Smad3 knockout mice and cells in which deletion of Smad3 protects against SARS-CoV-2 N protein-induced cell death and AKI in vivo and in vitro. Most significantly, it is also found that targeting Smad3 with a Smad3 pharmacological inhibitor is able to inhibit SARS-CoV-2 N-induced AKI. In conclusion, the authors identify that SARS-CoV-2 N protein is a key mediator for AKI and induces AKI via the Smad3-dependent G1 cell cycle arrest mechanism. Targeting Smad3 may represent as a novel therapy for COVID-19-asscoaited AKI.