The role of Neuropilin-1 in COVID-19.

Neuropilin-1 (NRP-1), a member of a family of signaling proteins, was shown to serve as an entry factor and potentiate SARS Coronavirus 2 (SARS-CoV-2) infectivity in vitro. This cell surface receptor with its disseminated expression is important in angiogenesis, tumor progression, viral entry, axonal guidance, and immune function. NRP-1 is implicated in several aspects of a SARS-CoV-2 infection including possible spread through the olfactory bulb and into the central nervous system and increased NRP-1 RNA expression in lungs of severe Coronavirus Disease 2019 (COVID-19). Up-regulation of NRP-1 protein in diabetic kidney cells hint at its importance in a population at risk of severe COVID-19. Involvement of NRP-1 in immune function is compelling, given the role of an exaggerated immune response in disease severity and deaths due to COVID-19. NRP-1 has been suggested to be an immune checkpoint of T cell memory. It is unknown whether involvement and up-regulation of NRP-1 in COVID-19 may translate into disease outcome and long-term consequences, including possible immune dysfunction. It is prudent to further research NRP-1 and its possibility of serving as a therapeutic target in SARS-CoV-2 infections. We anticipate that widespread expression, abundance in the respiratory and olfactory epithelium, and the functionalities of NRP-1 factor into the multiple systemic effects of COVID-19 and challenges we face in management of disease and potential long-term sequelae.

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.

Expression of the SARS-CoV-2 Receptor ACE2 in Human Retina and Diabetes-Implications for Retinopathy.

Purpose: To investigate the expression of angiotensin-converting enzyme 2 (ACE2), the receptor for SARS-CoV-2 in human retina. Methods: Human post-mortem eyes from 13 non-diabetic control cases and 11 diabetic retinopathy cases were analyzed for the expression of ACE2. To compare the vascular ACE2 expression between different organs that involve in diabetes, the expression of ACE2 was investigated in renal specimens from nondiabetic and diabetic nephropathy patients. Expression of TMPRSS2, a cell-surface protease that facilitates SARS-CoV-2 entry, was also investigated in human nondiabetic retinas. Primary human retinal endothelial cells (HRECs) and primary human retinal pericytes (HRPCs) were further used to confirm the vascular ACE2 expression in human retina. Results: We found that ACE2 was expressed in multiple nonvascular neuroretinal cells, including the retinal ganglion cell layer, inner plexiform layer, inner nuclear layer, and photoreceptor outer segments in both nondiabetic and diabetic retinopathy specimens. Strikingly, we observed significantly more ACE2 positive vessels in the diabetic retinopathy specimens. By contrast, in another end-stage organ affected by diabetes, the kidney, ACE2 in nondiabetic and diabetic nephropathy showed apical expression of ACE2 tubular epithelial cells, but no endothelial expression in glomerular or peritubular capillaries. Western blot analysis of protein lysates from HRECs and HRPCs confirmed expression of ACE2. TMPRSS2 expression was present in multiple retinal neuronal cells, vascular and perivascular cells, and Müller glia. Conclusions: Together, these results indicate that retina expresses ACE2 and TMPRSS2. Moreover, there are increased vascular ACE2 expression in diabetic retinopathy retinas.

Identification of a special cell type as a determinant of the kidney tropism of SARS-CoV-2.

The kidney tropism of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been well-validated clinically and often leads to various forms of renal damage in coronavirus disease-2019 (COVID-19) patients. However, the underlying mechanisms and diagnostic approaches remain to be determined. We interrogated the expression of virus-related host factors in single-cell RNA sequencing (scRNA-seq) datasets of normal human kidneys and kidneys with pre-existing diseases and validated the results with urinary proteomics of COVID-19 patients and healthy individuals. We also assessed the effects of genetic variants on kidney susceptibility using expression quantitative trait loci (eQTLs) databases. We identified a subtype of tubular cells, which we named PT-3 cells, as being vulnerable to SARS-CoV-2 infections in the kidneys. PT-3 cells were enriched in viral entry factors and replication and assembly machinery but lacked antiviral restriction factors. Immunohistochemistry confirmed positive staining of PT-3 cell marker SCL36A2 on kidney sections from COVID-19 patients. Urinary proteomic analyses of COVID-19 patients revealed that markers of PT-3 cells were significantly increased, along with elevated viral receptor angiotensin-converting enzyme 2. We further found that the proportion of PT-3 cells increased in diabetic nephropathy but decreased in kidney allografts and lupus nephropathy, suggesting that kidney susceptibility varied among these diseases. We finally identified several eQTLs that regulate the expression of host factors in kidney cells. PT-3 cells may represent a key determinant for the kidney tropism of SARS-CoV-2, and detection of PT-3 cells may be used to assess the risk of renal infection during COVID-19.

Hepatitis C virus-related kidney disease: various histological patterns.

BACKGROUND: Although hepatitis C virus (HCV) infection is known to be associated with Type 2 cryoglobulinemic glomerulopathy (CG), only a few reports about other types of nephropathy have been published. METHODS: 68 HCV antibody positive patients in whom renal biopsy had been performed for persistent proteinuria, hematuria, and/or renal dysfunction between 1992 and 2008 at our institute were included. The histological, clinical and laboratory characteristics including the age, gender, hypertension, diabetes mellitus, liver histology (chronic hepatitis or liver cirrhosis), HCV-RNA, HCV genotype, splenomegaly, gastroesophageal varices, serum creatinine, hemoglobin, platelet count, rheumatoid factor, cryoglobulin, IgG, IgA, IgM, CH50, C3, C4, creatinine clearance, 24-h protein excretion, and hematuria, between their nephropathy with and without immune deposition were compared. RESULTS: Nephropathy was classified into two groups based on the detection of immune deposits by immunofluorescence microscopy: i.e., a positive group (n = 39) and a negative group (n = 29). The former group was further classified into three types of nephropathy: IgG dominant group (n = 10) (including membranous nephropathy (MN)), IgA dominant group (n = 20) (including IgA nephropathy (IgAN)), membranoproliferative glomerulonephritis (MPGN) (IgA type)), and IgM dominant group (n = 9) (MPGN apart from the IgA type). The latter group included diabetic nephropathy (n = 13), focal glomerular sclerosis (n = 4), and benign nephrosclerosis (n = 3), malignant nephrosclerosis (n = 1), tubulointerstitial nephritis (TIN) (n = 2), minimal change nephrotic syndrome (n = 1), cast nephropathy (n = 1), granulomatous TIN (n = 1), and others (n = 3). An increased serum IgM level, hypocomplementemia, splenomegaly, thrombocytopenia, liver cirrhosis, hematuria, and a high HCV RNA level were features of patients with MPGN of IgM dominant group (consistent with "CG"). CONCLUSIONS: Our results showed various histological patterns of HCV-related kidney disease and the specificity of CG, and revealed that a minority of HCV patients (n = 7) presented typical CG, while IgAN, MN, and diabetic nephropathy were more frequent.

JC Viruria Is Associated With Reduced Risk of Diabetic Kidney Disease.

PURPOSE: African Americans who shed JC polyomavirus (JCV) in their urine have reduced rates of nondiabetic chronic kidney disease (CKD). We assessed the associations between urinary JCV and urine BK polyomavirus (BKV) with CKD in African Americans with diabetes mellitus. METHODS: African Americans with diabetic kidney disease (DKD) and controls lacking nephropathy from the Family Investigation of Nephropathy and Diabetes Consortium (FIND) and African American-Diabetes Heart Study (AA-DHS) had urine tested for JCV and BKV using quantitative PCR. Of the 335 individuals tested, 148 had DKD and 187 were controls. RESULTS: JCV viruria was detected more often in the controls than in the patients with DKD (FIND: 46.6% vs 32.2%; OR, 0.52; 95% CI, 0.29 to 0.93; P = 0.03; AA-DHS: 30.4% vs 26.2%; OR, 0.63; 95% CI, 0.27 to 1.48; P = 0.29). A joint analysis adjusted for age, sex, and study revealed that JC viruria was inversely associated with DKD (OR, 0.56; 95% CI, 0.35 to 0.91; P = 0.02). Statistically significant relationships between BKV and DKD were not observed. MAIN CONCLUSIONS: The results from the present study extend the inverse association between urine JCV and nondiabetic nephropathy in African Americans to DKD. These results imply that common pathways likely involving the innate immune system mediate coincident chronic kidney injury and restriction of JCV replication. Future studies are needed to explore causative pathways and characterize whether the absence of JC viruria can serve as a biomarker for DKD in the African American population.

Idiopathic nodular glomerulosclerosis (ING) in an African American (AA) man with hepatitis C.

Idiopathic nodular glomerulosclerosis (ING) in a non-diabetic patient is uncommon. Nodular glomerulosclerosis is hallmark sign of diabetic nephropathy. ING is a very rare clinicopathological disease associated with smoking, obesity and hypertension, chronic obstructive pulmonary disease and metabolic syndrome. A 68-year-old non-obese African American man with hypertension, smoking and history of hepatitis C presented to the clinic with progressive worsening of lower extremity oedema and declining renal function over few months. Renal biopsy demonstrated nodular glomerulosclerosis. In this case, ING is hypothesised to be associated with hepatitis C along with smoking and hypertension (HTN). We present this case to speculate the existence of yet unknown aetiologies of ING.

Inauspicious contribution of hepatitis C virus and diabetes mellitus targeting kidneys: an update.

Hepatitis C virus (HCV) infection and diabetes mellitus are frequent problems worldwide that induce high health and financial burden in different societies, both of which are also highly prevalent in patients with chronic kidney disease. Diabetes mellitus is a known underlying cause of end-stage renal disease, and on the other hand, HCV is responsible for a wide variety of renal manifestations, such as membranous nephropathy, cryoglobulinemia, and membranoproliferative glomerulonephritis. Moreover, along with its direct impact on kidney damage, HCV is also known to play a role in progression of other causes of kidney diseases. It is known that HCV infection is highly prevalent among patients with diabetic nephropathy. This article reviews the existing literature on the relationship between HCV infection and diabetes mellitus in patients with chronic kidney disease, and also overviews the interplay of these two factors in the transplantation era.

Patterns in the prevalence of hepatitis C virus infection at the start of hemodialysis in Japan.

BACKGROUND: Although hepatitis C virus (HCV) infection is a persistent public health concern in hemodialysis patients, there seem to have been only a few reports on the prevalence of HCV at the start of hemodialysis. In this study we investigated whether patients starting on hemodialysis therapy are positive for anti-HCV antibody or not. METHODS: The 400 patients who began regular hemodialysis between February 2003 and June 2007 were enrolled in this study. Clinical data such as age, anti-HCV antibody and primary cause of end-stage kidney disease (ESKD) were examined. As healthy controls we used 70,717 healthy blood donors in 2005 whose data were obtained from Tokyo Metropolitan Red Cross Blood Center. Anti-HCV antibody was used as an indicator of HCV infection. Since the prevalence of HCV infection is affected by age in Japan, we classified the patients by age group. RESULTS: The anti-HCV antibody prevalence rate among the patients who were new to hemodialysis was 7.3%, as opposed to 0.15% in the healthy volunteers. The prevalence of HCV in the 31-45-, 46-60-, and 61-year-old groups was significantly higher among the hemodialysis patients than among the healthy volunteers (P = 0.0209, <0.0001, and <0.0001, respectively). The prevalence rate of anti-HCV antibody was higher among men (10.0%) than among women (1.5%, P < 0.0001) in the hemodialysis patients. The anti-HCV-antibody-positive patients were significantly older than the anti-HCV-antibody-negative patients (66.4 +/- 14.3 years versus 58.6+/-16.6 years; P = 0.0152). Diabetic nephropathy was a more frequent cause of ESKD among the anti-HCV-antibody-positive patients (30.4%) than among the anti-HCV-antibody-negative patients (19.9%, P = 0.0122). Among the anti-HCV-antibody-positive patients, 55.2% had received a blood transfusion. The rate was significantly higher than that among the anti-HCV-antibody-negative patients (19.4%, P < 0.0001). CONCLUSION: The results showed a much higher rate of anti-HCV antibody positivity in patients new to hemodialysis than in healthy volunteers. Older age, blood transfusion, male gender, and diabetic nephropathy seemed to be risk factors for anti-HCV antibody positivity in Japan.

Seroprevalence of hepatitis C in patients with type 2 diabetes mellitus and non-diabetic on haemodialysis.

Type 2 diabetes mellitus (DM) has emerged as the commonest cause of end-stage renal disease. Haemodialysis (HD) treatment constitutes a high-risk environment for the transmission of hepatitis C virus (HCV). The aim of this study was to establish a potential relationship between type 2 DM and HCV infection in HD patients. Of the 267 HD patients, 67 (25.1%) had type 2 DM and 200 (74.9%) were with diverse aetiology for end-stage renal disease. The serum markers of HCV infection were tested by a second-generation enzyme-linked immunosorbent assay test for antibodies and by qualitative reverse-transcription polymerase chain reaction technique for viral RNA. The overall prevalence of anti-HCV antibodies and HCV RNA was found to be 12.7% (34/267) and 10.1% (27/267), respectively. Patients with type 2 DM were found to have a higher HCV prevalence compared with non-diabetic patients [20.8% (14/67) vs. 10% (20/200)] (p < 0.05). The mean period on dialysis of anti-HCV-positive patients with type 2 DM was shorter than that observed for anti-HCV-positive non-diabetic patients (43.9 +/- 9.8 months vs. 59.7 +/- 28.4 months) (p < 0.05). This study has shown that although the period on dialysis of diabetic patients are shorter than non-diabetic patients, the prevalence of HCV in HD patients with type 2 DM is higher than that detected in non-diabetic HD patients.

Prevalence of hepatitis C in patients with idiopathic glomerulopathies in native and transplant kidneys.

Previous studies suggest that there is an association between hepatitis C (HCV) infection and glomerular diseases in native and transplanted kidneys. However, the data are controversial. To reexamine this issue, we determined the prevalence of serum anti-HCV antibodies in patients with glomerulopathies of native kidneys (n = 105) and in patients with acute and chronic transplant glomerulopathy (TxGN) (n = 62). Compared with a control group of patients with diabetic nephropathy (n = 37, 0% HCV+), the prevalence of HCV antibodies was significantly higher in patients with focal glomerulosclerosis (FGS) (4 of 32, 13%, P = 0.04 by chi-square), but not in patients with membranous nephropathy (MGN) (1 of 19, 5%) or in patients with membranoproliferative glomerulonephritis (MPGN) (2 of 17, 12%). All of the patients with positive HCV serology had histories of intravenous (IV) drug use. Thus, HCV serology was negative in all of the patients with native glomerulopathies without histories of IV drug use. Compared with a group of 105 transplant patients without TxGN (1.8% HCV+), the prevalence of HCV antibodies was significantly higher in patients with acute (A)TxGN (12 or 41: 29%. P = 0.0004) and in patients with chronic (C)TxGN (9 of 27: 33%. P = 0.0004). Compared with controls, patients with ATxGN also had a significantly higher prevalence of serum immunoglobulin (Ig) M antibodies to cytomegalovirus (CMV) (3% and 26% of patients, respectively, P = 0.0004). However, there were no statistical associations between HCV and CMV serologies. These results do not support the postulate that HCV infection is associated with idiopathic native glomerulopathies; instead, the data suggest that the presence of HCV positivity in these patients can be explained by the inclusion of patients with a history of IV drug use. In contrast, these studies demonstrate for the first time an association between HCV infection and transplant glomerulopathies.