In-silico analysis of interacting pathways through KIM-1 protein interaction in diabetic nephropathy.

BACKGROUND: Human Kidney Injury Molecule-1, also known as HAVCR-1 (Hepatitis A virus cellular receptor 1), belongs to the cell-surface protein of immunoglobulin superfamily involved in the phagocytosis by acting as scavenger receptor epithelial cells. The study focused on pinpointing the mechanisms and genes that interact with KIM-1. METHODS: This in-silico study was done from March 2019 to December 2019. The Enrichment and protein-protein interaction (PPI) network carefully choose proteins. In addition, the diagramed gene data sets were accomplished using FunRich version 3.1.3. It was done to unveil the proteins that may affect the regulation of HAVCR1 or may be regulated by this protein. These genes were then further considered in pathway analysis to discover the dysregulated pathways in diabetic nephropathy. The long list of differentially expressed genes is meaningless without pathway analysis. RESULTS: Critical pathways that are dysregulated in diabetic nephropathy patients have been identified. These include Immune System (Total = 237, P < 0.05), Innate Immune System (Total = 140, P < 0.05), Cytokine Signaling Immune system (Total = 116, P < 0.05), Adaptive Immune System (Total = 85) and Neutrophil degranulation (Total = 78). CONCLUSION: The top 5 genes that are interacting directly with HIVCR1 include CASP3, CCL2, SPP1, B2M, and TIMP1 with degrees 161, 144, 108, 107, and 105 respectively for Immune system pathways (Innate Immune System, Cytokine Signaling Immune system, Adaptive Immune System and Neutrophil degranulation).

Kim-1 Targeted Extracellular Vesicles: A New Therapeutic Platform for RNAi to Treat AKI.

BACKGROUND: AKI is a significant public health problem with high morbidity and mortality. Unfortunately, no definitive treatment is available for AKI. RNA interference (RNAi) provides a new and potent method for gene therapy to tackle this issue. METHODS: We engineered red blood cell-derived extracellular vesicles (REVs) with targeting peptides and therapeutic siRNAs to treat experimental AKI in a mouse model after renal ischemia/reperfusion (I/R) injury and unilateral ureteral obstruction (UUO). Phage display identified peptides that bind to the kidney injury molecule-1 (Kim-1). RNA-sequencing (RNA-seq) characterized the transcriptome of ischemic kidney to explore potential therapeutic targets. RESULTS: REVs targeted with Kim-1-binding LTH peptide (REVLTH) efficiently homed to and accumulated at the injured tubules in kidney after I/R injury. We identified transcription factors P65 and Snai1 that drive inflammation and fibrosis as potential therapeutic targets. Taking advantage of the established REVLTH, siRNAs targeting P65 and Snai1 were efficiently delivered to ischemic kidney and consequently blocked the expression of P-p65 and Snai1 in tubules. Moreover, dual suppression of P65 and Snai1 significantly improved I/R- and UUO-induced kidney injury by alleviating tubulointerstitial inflammation and fibrosis, and potently abrogated the transition to CKD. CONCLUSIONS: A red blood cell-derived extracellular vesicle platform targeted Kim-1 in acutely injured mouse kidney and delivered siRNAs for transcription factors P65 and Snai1, alleviating inflammation and fibrosis in the tubules.

LncRNA-ATB participates in the regulation of calcium oxalate crystal-induced renal injury by sponging the miR-200 family.

BACKGROUND: LncRNA-ATB is a long noncoding RNA (lncRNA) activated by transforming growth factor ß (TGF-ß) and it has important biological functions in tumours and nontumour diseases. Meanwhile, TGF-ß is the most critical regulatory factor in the process of nephrotic fibrosis and calcium oxalate (CaOx) crystal-induced renal injury. The present study aimed to investigate the biological function and mechanism of lncRNA-ATB in CaOx crystal-induced renal injury. METHODS: The expression level of lncRNA-ATB was detected by quantitative reverse-transcription polymerase chain reaction (qRT-PCR), the expression levels of epithelial-mesenchymal transition (EMT) markers, TGF-ß1 and Kidney Injury Molecule-1 (KIM-1) were detected by qRT-PCR, immunofluorescence staining or western blot analysis, cell proliferation was measured with a CCK-8 kit, cell apoptosis was measured by flow cytometry and TUNEL staining, and cell injury was detected with the Cytotoxicity lactate dehydrogenase (LDH) Assay kit and the expression level of KIM-1. RESULTS: The expression levels of lncRNA-ATB and TGF-ß1 were significantly increased in HK-2 cells after coincubation with calcium oxalate monohydrate (COM). COM stimulation caused significant injury in the HK-2 cells, induced cell apoptosis, inhibited cell proliferation, and induced EMT changes. After COM stimulation, the expression levels of the epithelial cell markers E-cadherin and zonula occludens (ZO)-1 in HK-2 cells significantly decreased, whereas the levels of the mesenchymal cell markers N-cadherin, vimentin and α-smooth muscle actin (α-SMA) significantly increased. Interference with lncRNA-ATB expression significantly relieved the COM-induced cell injury, cell apoptosis, proliferation inhibition, and EMT changes. The expression levels of the microRNA-200 (miR-200) family in the HK-2 cells after coincubation with COM were significantly decreased. MiR-200a mimics relieved the COM-induced cell injury, apoptosis, proliferation inhibition, and EMT changes, whereas miR-200a inhibitors abolished the lncRNA-ATB interference-induced relief of the COM-induced cell injury, apoptosis, proliferation inhibition, and EMT. CONCLUSION: LncRNA-ATB promoted the COM-induced cell injury, cell apoptosis, proliferation inhibition, and EMT to participate in the process of CaOx crystal-induced renal injury by sponging miR-200s.

Porcine Reproductive and Respiratory Syndrome Virus Utilizes Viral Apoptotic Mimicry as an Alternative Pathway To Infect Host Cells.

Porcine reproductive and respiratory syndrome (PRRS), caused by PRRS virus (PRRSV), has led to enormous economic losses in global swine industry. Infection by PRRSV is previously shown to be via low pH-dependent clathrin-mediated endocytosis, and CD163 functions as an essential receptor during viral infection. Despite much research focusing on it, PRRSV infection remains to be fully elucidated. In this study, we demonstrated that PRRSV externalized phosphatidylserine (PS) on the envelope as viral apoptotic mimicry and infected host cells through T-cell immunoglobulin and mucin domain (TIM)-induced and CD163-involved macropinocytosis as an alternative pathway. In detail, we identified that PS receptor TIM-1/4 recognized and interacted with PRRSV as viral apoptotic mimicry and subsequently induced macropinocytosis by the downstream Rho GTPases Rac1, cell division control protein 42 (Cdc42), and p21-activated kinase 1 (Pak1). Altogether, these results expand our knowledge of PRRSV infection, which will support implications for the prevention and control of PRRS.IMPORTANCE PRRS has caused huge economic losses to pig farming worldwide. Its causative agent, PRRSV, infects host cells through low pH-dependent clathrin-mediated endocytosis and CD163 is indispensable during the process. Whether there exist alternative infection pathways for PRRSV arouses our interest. Here, we found that PRRSV exposed PS on its envelope and disguised as apoptotic debris. The PS receptor TIM-1/4 recognized PRRSV and induced the downstream signaling pathway to mediate viral infection via CD163-dependent macropinocytosis. The current work deepens our understanding of PRRSV infection and provides clues for the development of drugs and vaccines against the virus.

Association of TIM-1 (T-Cell Immunoglobulin and Mucin Domain 1) With Incidence of Stroke.

OBJECTIVE: The aim of this study was to investigate if there is a causal relationship between circulating levels of TIM-1 (T-cell immunoglobulin and mucin domain 1) and incidence of stroke. Approach and Results: Plasma TIM-1 was analyzed in 4591 subjects (40% men; mean age, 57.5 years) attending the Malmö Diet and Cancer Study. Incidence of stroke was studied in relation to TIM-1 levels during a mean of 19.5 years follow-up. Genetic variants associated with TIM-1 (pQTLs [protein quantitative trait loci]) were examined, and a 2-sample Mendelian randomization analysis was performed to explore the role of TIM-1 in stroke using summary statistics from our pQTLs and the MEGASTROKE consortium. A total of 416 stroke events occurred during follow-up, of which 338 were ischemic strokes. After risk factor adjustment, TIM-1 was associated with increased incidence of all-cause stroke (hazards ratio for third versus first tertile, 1.44 [95% CI, 1.10-1.87]; P for trend, 0.004), and ischemic stroke (hazards ratio, 1.42 [95% CI, 1.06-1.90]; P for trend, 0.011). Nineteen independent lead SNPs, located in three genomic risk loci showed significant associations with TIM-1 (P<5×10-8). A 2-sample Mendelian Randomization analysis suggested a causal effect of TIM-1 on stroke (ß=0.083, P=0.0004) and ischemic stroke (ß=0.102, P=7.7×10-5). CONCLUSIONS: Plasma level of TIM-1 is associated with incidence of stroke. The genetic analyses suggest that this could be a causal relationship.

Predictive value of novel biomarkers for chronic kidney disease among workers occupationally exposed to silica.

There is a pressing need to find reliable biomarkers for the early diagnosis of silica-induced nephropathy. Abundant genes are upregulated in damaged kidneys with subsequent protein products appearing in the urine. Liver-type fatty acid-binding protein (L-FABP) and kidney injury molecule-1 (KIM-1) are among the most promising. Our objective was to study the importance of L-FABP and KIM-1 genes and their urinary proteins in the early detection of silica-induced renal injury, as compared with other conventional biomarkers. A cross-sectional study was conducted among 90 pottery workers occupationally exposed to silica, as compared to 90 controls. A full history taking and complete clinical examination were performed. Levels of serum creatinine, liver enzymes, urinary silicon, KIM-1, and L-FABP gene expression and protein products were measured. Estimated glomerular filtration rate (eGFR) was calculated, and abdominal ultrasound was performed. The results showed that the silica-exposed group had a statistically significant increase in serum creatinine and urinary silica, as well as a significant decrease in eGFR. Additionally, a significant increase in KIM-1 and L-FABP gene expression, associated with a significant increase in their urinary protein, was found among the exposed group. A positive correlation between urinary silica level and L-FABP gene expression was also found. A receiver operating characteristic curve analysis for L-FABP and KIM-1 gene as predictors for silica-induced nephropathy showed that L-FABP gene and protein specificity were greater than the KIM-1 gene and protein. Taken together, these findings suggest that the L-FABP gene and its protein product may be used as early indicators for renal injury among silica exposed workers.

Class IIa HDAC inhibitor TMP195 alleviates lipopolysaccharide-induced acute kidney injury.

Sepsis-associated acute kidney injury (SA-AKI) is associated with high mortality rates, but clinicians lack effective treatments except supportive care or renal replacement therapies. Recently, histone deacetylase (HDAC) inhibitors have been recognized as potential treatments for acute kidney injury and sepsis in animal models; however, the adverse effect generated by the use of pan inhibitors of HDACs may limit their application in people. In the present study, we explored the possible renoprotective effect of a selective class IIa HDAC inhibitor, TMP195, in a murine model of SA-AKI induced by lipopolysaccharide (LPS). Administration of TMP195 significantly reduced increased serum creatinine and blood urea nitrogen levels and renal damage induced by LPS; this was coincident with reduced expression of HDAC4, a major isoform of class IIa HDACs, and elevated histone H3 acetylation. TMP195 treatment following LPS exposure also reduced renal tubular cell apoptosis and attenuated renal expression of neutrophil gelatinase-associated lipocalin and kidney injury molecule-1, two biomarkers of tubular injury. Moreover, LPS exposure resulted in increased expression of BAX and cleaved caspase-3 and decreased expression of Bcl-2 and bone morphogenetic protein-7 in vivo and in vitro; TMP195 treatment reversed these responses. Finally, TMP195 inhibited LPS-induced upregulation of multiple proinflammatory cytokines/chemokines, including intercellular adhesion molecule-1, monocyte chemoattractant protein-1, tumor necrosis factor-α, and interleukin-1ß, and accumulation of inflammatory cells in the injured kidney. Collectively, these data indicate that TMP195 has a powerful renoprotective effect in SA-AKI by mitigating renal tubular cell apoptosis and inflammation and suggest that targeting class IIa HDACs might be a novel therapeutic strategy for the treatment of SA-AKI that avoids the unintended adverse effects of a pan-HDAC inhibitor.

Evaluation of cisplatin-induced injury in human kidney organoids.

Acute kidney injury (AKI) remains a major global healthcare problem, and there is a need to develop human-based models to study AKI in vitro. Toward this goal, we have characterized induced pluripotent stem cell-derived human kidney organoids and their response to cisplatin, a chemotherapeutic drug that induces AKI and preferentially damages the proximal tubule. We found that a single treatment with 50 µM cisplatin induces hepatitis A virus cellular receptor 1 (HAVCR1) and C-X-C motif chemokine ligand 8 (CXCL8) expression, DNA damage (γH2AX), and cell death in the organoids but greatly impairs organoid viability. DNA damage was not specific to the proximal tubule but also affected the distal tubule and interstitial cell populations. This lack of specificity correlated with low expression of proximal tubule-specific SLC22A2/organic cation transporter 2 (OCT2) for cisplatin. To improve viability, we developed a repeated low-dose regimen of 4 × 5 µM cisplatin over 7 days and found this caused less toxicity while still inducing a robust injury response that included secretion of known AKI biomarkers and inflammatory cytokines. This work validates the use of human kidney organoids to model aspects of cisplatin-induced injury, with the potential to identify new AKI biomarkers and develop better therapies.

Identification, expression pattern, and immune response of Tim-1 and Tim-4 in embryos and adult medaka (Oryzias latipes).

T-cell immunoglobulin (Ig) and mucin domain-containing 1 (Tim-1) and Tim-4 are two members of the Tim family. In mammals, Tim-1 and Tim-4 are proteins mainly expressed in immune cells and are associated with immune response. In the present study, medaka Oryzias latipes' Tim-1 (OlTim-1) and OlTim-4 were identified and characterized using bioinformatics analyses. With the use of reverse-transcription polymerase chain reaction, the expression profiles of OlTim-1 and OlTim-4 were examined in embryos and adult fish and in immune tissues following the intraperitoneal injection of stimulants. The results revealed that OlTim-1 possesses a cytoplasmic region, a transmembrane region, a mucin domain, and an Ig-like domain, while OlTim-4 is composed of two Ig-like domains and a mucin domain, but without the transmembrane region and cytoplasmic region. OlTim-1 and OlTim-4 expressions are detectable from the gastrula stage on, indicating that they are zygotic genes. Furthermore, OlTim-1 and OlTim-4 are expressed ubiquitously in the adult. Administration of immune stimulants, namely lipopolysaccharides and polyinosinic:polycytidylic acid, significantly increased the expression levels of OlTim-1 and OlTim-4 in the liver and intestine within 1 day and in the head, kidney, and spleen within 3 to 4 days postinjection. These results suggest that OlTim-1 and OlTim-4 are possibly involved in both innate and adaptive immunities.

Novel insights into the disease transcriptome of human diabetic glomeruli and tubulointerstitium.

BACKGROUND: Diabetic nephropathy (DN) is the most common cause of end-stage renal disease, affecting ∼30% of the rapidly growing diabetic population, and strongly associated with cardiovascular risk. Despite this, the molecular mechanisms of disease remain unknown. METHODS: RNA sequencing (RNAseq) was performed on paired, micro-dissected glomerular and tubulointerstitial tissue from patients diagnosed with DN [n = 19, 15 males, median (range) age: 61 (30-85) years, chronic kidney disease stages 1-4] and living kidney donors [n = 20, 12 males, median (range) age: 56 (30-70) years]. RESULTS: Principal component analysis showed a clear separation between glomeruli and tubulointerstitium transcriptomes. Differential expression analysis identified 1550 and 4530 differentially expressed genes, respectively (adjusted P < 0.01). Gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses highlighted activation of inflammation and extracellular matrix (ECM) organization pathways in glomeruli, and immune and apoptosis pathways in tubulointerstitium of DN patients. Specific gene modules were associated with renal function in weighted gene co-expression network analysis. Increased messengerRNA (mRNA) expression of renal damage markers lipocalin 2 (LCN) and hepatitis A virus cellular receptor1 (HAVCR1) in the tubulointerstitial fraction was observed alongside higher urinary concentrations of the corresponding proteins neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) in DN patients. CONCLUSIONS: Here we present the first RNAseq experiment performed on paired glomerular and tubulointerstitial samples from DN patients. We show that prominent disease-specific changes occur in both compartments, including relevant cellular processes such as reorganization of ECM and inflammation (glomeruli) as well as apoptosis (tubulointerstitium). The results emphasize the potential of utilizing high-throughput transcriptomics to decipher disease pathways and treatment targets in this high-risk patient population.

Pre-Operative Fasting Provides Long Term Protection Against Chronic Renal Damage Induced by Ischaemia Reperfusion Injury in Wild Type and Aneurysm Prone Fibulin-4 Mice.

OBJECTIVE: Renal ischaemia reperfusion injury (IRI) is inevitable during open repair of pararenal aortic aneurysms. Pre-operative fasting potently increases resistance against IRI. The effect of fasting on IRI was examined in a hypomorphic Fibulin-4 mouse model (Fibulin-4+/R), which is predisposed to develop aortic aneurysms. METHODS: Wild type (WT) and Fibulin-4+/R mice were either fed ad libitum (AL) or fasted for two days before renal IRI induction by temporary clamping of the renal artery and vein of both kidneys. Six hours, 48 h, and seven days post-operatively, serum urea levels, renal histology, and mRNA expression levels of inflammatory and injury genes were determined to assess kidney function and damage. Additionally, matrix metalloproteinase activity in the kidney was assessed six months after IRI. RESULTS: Two days of fasting improved survival the first week after renal IRI in WT mice compared with AL fed mice. Short term AL fed Fibulin-4+/R mice showed improved survival and kidney function compared with AL fed WT mice, which could not be further enhanced by fasting. Both fasted WT and Fibulin-4+/R mice showed improved survival, kidney function and morphology compared with AL fed mice six months after renal IRI. Fibulin-4+/R kidneys of fasted mice showed reduced apoptosis together with increased matrix metalloprotease activity levels compared with AL fed Fibulin-4+/R mice, indicative of increased matrix remodelling. CONCLUSION: Fibulin-4+/R mice are naturally protected against the short-term, but not long-term, consequences of renal IRI. Pre-operative fasting protects against renal IRI and prevents (long-term) deterioration of kidney function and morphology in both WT and Fibulin-4+/R mice. These data suggest that pre-operative fasting may decrease renal damage in patients undergoing open abdominal aneurysm repair.

Genetic polymorphisms of rs9313422 G>C and rs41297579 G>A at the promoter of TIM-1 gene contribute to the risk of community-acquired pneumonia in children.

OBJECTIVE: To investigate the association of genetic polymorphisms of rs9313422 G>C and rs41297579 G>A at the promoter of TIM-1 gene with the risk of community-acquired pneumonia (CAP) in children. METHODS: A total of 112 children with CAP were included as the case group. Another 120 healthy children were enrolled as the control group. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was applied for the genotyping of rs9313422 G>C and rs41297579 G>A in the promoter region of TIM-1. RESULTS: rs9313422 G>C was related to the risk of CAP in children under codominant model, dominant model, recessive model, and allele model. Besides, the A allele of rs41297579 G>A could increase the risk of CAP in children. Besides, the haplotype GA (rs9313422-rs41297579) and GG reduced the risk of children CAP, while haplotype CA had an elevated risk. rs9313422 G>C and rs41297579 G>A polymorphisms were both associated with the severity of CAP in children, and the rs9313422 G>C was also related to the ICU admission rate. In addition, patients carried with the mutant homozygotes of rs9313422 G>C and rs41297579 G>A showed higher levels of white blood cell (WBC), procalcitonin (PCT), and C-reactive protein (CRP) than the wild type and heterozygous genotypes carriers. CONCLUSION: rs9313422 G>C and rs41297579 G>A polymorphisms in the promoter region of TIM-1 could increase the risk of CAP in children and showed a relation with inflammatory responses and severity.

Roles Played by Biomarkers of Kidney Injury in Patients with Upper Urinary Tract Obstruction.

Partial or complete obstruction of the urinary tract is a common and challenging urological condition caused by a variety of conditions, including ureteral calculi, ureteral pelvic junction obstruction, ureteral stricture, and malignant ureteral obstruction. The condition, which may develop in patients of any age, induces tubular and interstitial injury followed by inflammatory cell infiltration and interstitial fibrosis, eventually impairing renal function. The serum creatinine level is commonly used to evaluate global renal function but is not sensitive to early changes in the glomerular filtration rate and unilateral renal damage. Biomarkers of acute kidney injury are useful for the early detection and monitoring of kidney injury induced by upper urinary tract obstruction. These markers include levels of neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemotactic protein-1, kidney injury molecule 1, N-acetyl-b-D-glucosaminidase, and vanin-1 in the urine and serum NGAL and cystatin C concentrations. This review summarizes the pathophysiology of kidney injury caused by upper urinary tract obstruction, the roles played by emerging biomarkers of obstructive nephropathy, the mechanisms involved, and the clinical utility and limitations of the biomarkers.

High-Density Lipoprotein (HDL) Inhibits Serum Amyloid A (SAA)-Induced Vascular and Renal Dysfunctions in Apolipoprotein E-Deficient Mice.

Serum amyloid A (SAA) promotes endothelial inflammation and dysfunction that is associated with cardiovascular disease and renal pathologies. SAA is an apoprotein for high-density lipoprotein (HDL) and its sequestration to HDL diminishes SAA bioactivity. Herein we investigated the effect of co-supplementing HDL on SAA-mediated changes to vascular and renal function in apolipoprotein E-deficient (ApoE-/-) mice in the absence of a high-fat diet. Male ApoE-/- mice received recombinant human SAA or vehicle (control) by intraperitoneal (i.p.) injection every three days for two weeks with or without freshly isolated human HDL supplemented by intravenous (i.v.) injection in the two weeks preceding SAA stimulation. Aorta and kidney were harvested 4 or 18 weeks after commencement of treatment. At 4 weeks after commencement of treatment, SAA increased aortic vascular cell adhesion molecule (VCAM)-1 expression and F2-isoprostane level and decreased cyclic guanosine monophosphate (cGMP), consistent with SAA stimulating endothelial dysfunction and promoting atherosclerosis. SAA also stimulated renal injury and inflammation that manifested as increased urinary protein, kidney injury molecule (KIM)-1, and renal tissue cytokine/chemokine levels as well as increased protein tyrosine chlorination and P38 MAPkinase activation and decreased in Bowman's space, confirming that SAA elicited a pro-inflammatory phenotype in the kidney. At 18 weeks, vascular lesions increased significantly in the cohort of ApoE-/- mice treated with SAA alone. By contrast, pretreatment of mice with HDL decreased SAA pro-inflammatory activity, inhibited SAA enhancement of aortic lesion size and renal function, and prevented changes to glomerular Bowman's space. Taken together, these data indicate that supplemented HDL reduces SAA-mediated endothelial and renal dysfunction in an atherosclerosis-prone mouse model.

Protective effect and mechanism of IL-10 on renal ischemia-reperfusion injury.

Interleukin (IL)-10, a cytokine with anti-inflammatory effects, is produced by blood cells and cells of various organs. Ischemia-reperfusion injury (IRI) is a systemic inflammatory disease caused by a systemic circulation of pro-inflammatory cytokines and chemokines produced from blood cells or organs damaged by ischemia. Apoptosis, a key event after IRI, is correlated with the degree of injury. Here we investigated the effects and mechanism of IL-10 in renal IRI. Compared to wild-type (WT) mice with a renal IRI, IL-10 knockout (IL-10 KO) mice with IRI demonstrated decreased renal function as represented by blood urea nitrogen and serum creatinine, upregulated early acute kidney injury (AKI) biomarkers such as kidney injury molecule-1 (Kim-1), increased mRNA expression of the pro-inflammatory cytokines IL-1ß, IL-6, and IL-18 and a chemokine (regulated on activation, normal T cell expressed and secreted; RANTES), and increased expression of the pro-apoptosis factors Bax and cleaved caspase-3. When tubular epithelial cells (TECs) from IL-10 KO mice were put in a hypoxic state and added with recombinant IL-10, their expression of Bax decreased. Our findings demonstrated that IL-10 suppressed the production of pro-inflammatory cytokines, renal dysfunction, and the expression of pro-apoptosis factors after IRI.

Determinants in the Ig Variable Domain of Human HAVCR1 (TIM-1) Are Required To Enhance Hepatitis C Virus Entry.

Hepatitis C virus (HCV) is the leading cause of chronic hepatitis in humans. Several host molecules participate in HCV cell entry, but this process remains unclear. The complete unraveling of the HCV entry process is important to further understand viral pathogenesis and develop therapeutics. Human hepatitis A virus (HAV) cellular receptor 1 (HAVCR1), CD365, also known as TIM-1, functions as a phospholipid receptor involved in cell entry of several enveloped viruses. Here, we studied the role of HAVCR1 in HCV infection. HAVCR1 antibody inhibited entry in a dose-dependent manner. HAVCR1 soluble constructs neutralized HCV, which did not require the HAVCR1 mucinlike region and was abrogated by a mutation of N to A at position 94 (N94A) in the Ig variable (IgV) domain phospholipid-binding pocket, indicating a direct interaction of the HAVCR1 IgV domain with HCV virions. However, knockout of HAVCR1 in Huh7 cells reduced but did not prevent HCV growth. Interestingly, the mouse HAVCR1 ortholog, also a phospholipid receptor, did not enhance infection and a soluble form failed to neutralize HCV, although replacement of the mouse IgV domain with the human HAVCR1 IgV domain restored the enhancement of HCV infection. Mutations in the cytoplasmic tail revealed that direct HAVCR1 signaling is not required to enhance HCV infection. Our data show that the phospholipid-binding function and other determinant(s) in the IgV domain of human HAVCR1 enhance HCV infection. Although the exact mechanism is not known, it is possible that HAVCR1 facilitates entry by stabilizing or enhancing attachment, leading to direct interactions with specific receptors, such as CD81.IMPORTANCE Hepatitis C virus (HCV) enters cells through a multifaceted process. We identified the human hepatitis A virus cellular receptor 1 (HAVCR1), CD365, also known as TIM-1, as a facilitator of HCV entry. Antibody blocking and silencing or knockout of HAVCR1 in hepatoma cells reduced HCV entry. Our findings that the interaction of HAVCR1 with HCV early during infection enhances entry but is not required for infection support the hypothesis that HAVCR1 facilitates entry by stabilizing or enhancing virus binding to the cell surface membrane and allowing the correct virus-receptor positioning for interaction with the main HCV receptors. Furthermore, our data show that in addition to the phospholipid-binding function of HAVCR1, the enhancement of HCV infection involves other determinants in the IgV domain of HAVCR1. These findings expand the repertoire of molecules that HCV uses for cell entry, adding to the already complex mechanism of HCV infection and pathogenesis.

HAVCR1 (CD365) and Its Mouse Ortholog Are Functional Hepatitis A Virus (HAV) Cellular Receptors That Mediate HAV Infection.

The hepatitis A virus (HAV) cellular receptor 1 (HAVCR1), classified as CD365, was initially discovered as an HAV cellular receptor using an expression cloning strategy. Due to the lack of HAV receptor-negative replication-competent cells, it was not possible to fully prove that HAVCR1 was a functional HAV receptor. However, biochemistry, classical virology, and epidemiology studies further supported the functional role of HAVCR1 as an HAV receptor. Here, we show that an anti-HAVCR1 monoclonal antibody that protected African green monkey kidney (AGMK) cells against HAV infection only partially protected monkey Vero E6 cells and human hepatoma Huh7 cells, indicating that these two cell lines express alternative yet unidentified HAV receptors. Therefore, we focused our work on AGMK cells to further characterize the function of HAVCR1 as an HAV receptor. Advances in clustered regularly interspaced short palindromic repeat/Cas9 technology allowed us to knock out the monkey ortholog of HAVCR1 in AGMK cells. The resulting AGMK HAVCR1 knockout (KO) cells lost susceptibility to HAV infection, including HAV-free viral particles (vpHAV) and exosomes purified from HAV-infected cells (exo-HAV). Transfection of HAVCR1 cDNA into AGMK HAVCR1 KO cells restored susceptibility to vpHAV and exo-HAV infection. Furthermore, transfection of the mouse ortholog of HAVCR1, mHavcr1, also restored the susceptibility of AGMK HAVCR1 KO cells to HAV infection. Taken together, our data clearly show that HAVCR1 and mHavcr1 are functional HAV receptors that mediate HAV infection. This work paves the way for the identification of alternative HAV receptors to gain a complete understanding of their interplay with HAVCR1 in the cell entry and pathogenic processes of HAV.IMPORTANCE HAVCR1, an HAV receptor, is expressed in different cell types, including regulatory immune cells and antigen-presenting cells. How HAV evades the immune response during a long incubation period of up to 4 weeks and the mechanism by which the subsequent necroinflammatory process clears the infection remain a puzzle that most likely involves the HAV-HAVCR1 interaction. Based on negative data, a recent paper from the S. M. Lemon and W. Maury laboratories (A. Das, A. Hirai-Yuki, O. Gonzalez-Lopez, B. Rhein, S. Moller-Tank, R. Brouillette, L. Hensley, I. Misumi, W. Lovell, J. M. Cullen, J. K. Whitmire, W. Maury, and S. M. Lemon, mBio 8:e00969-17, 2017, https://doi.org/10.1128/mBio.00969-17) suggested that HAVCR1 is not a functional HAV receptor, nor it is it required for HAV infection. However, our data, based on regain of the HAV receptor function in HAVCR1 knockout cells transfected with HAVCR1 cDNA, disagree with their findings. Our positive data show conclusively that HAVCR1 is indeed a functional HAV receptor and lays the ground for the identification of alternative HAV receptors and how they interact with HAVCR1 in cell entry and the pathogenesis of HAV.

TIM-1 Mediates Dystroglycan-Independent Entry of Lassa Virus.

Lassa virus (LASV) is an Old World arenavirus responsible for hundreds of thousands of infections in West Africa every year. LASV entry into a variety of cell types is mediated by interactions with glycosyltransferase LARGE-modified O-linked glycans present on the ubiquitous receptor α-dystroglycan (αDG). However, cells lacking αDG are permissive to LASV infection, suggesting that alternative receptors exist. Previous studies demonstrated that the phosphatidylserine (PtdSer)-binding receptors Axl and Tyro3 along with C-type lectin receptors mediate αDG-independent entry. Here, we demonstrate that another PtdSer receptor, TIM-1, mediates LASV glycoprotein (GP)-pseudotyped virion entry into αDG-knocked-out HEK 293T and wild-type (WT) Vero cells, which express αDG lacking appropriate glycosylation. To investigate the mechanism by which TIM-1 mediates enhancement of entry, we demonstrate that mutagenesis of the TIM-1 IgV domain PtdSer-binding pocket abrogated transduction. Furthermore, the human TIM-1 IgV domain-binding monoclonal antibody ARD5 blocked transduction of pseudovirions bearing LASV GP in a dose-dependent manner. Finally, as we showed previously for other viruses that use TIM-1 for entry, a chimeric TIM-1 protein that substitutes the proline-rich region (PRR) from murine leukemia virus envelope (Env) for the mucin-like domain served as a competent receptor. These studies provide evidence that, in the absence of a functional αDG, TIM-1 mediates the entry of LASV pseudoviral particles through interactions of virions with the IgV PtdSer-binding pocket of TIM-1.IMPORTANCE PtdSer receptors, such as TIM-1, are emerging as critical entry factors for many enveloped viruses. Most recently, hepatitis C virus and Zika virus have been added to a growing list. PtdSer receptors engage with enveloped viruses through the binding of PtdSer embedded in the viral envelope, defining them as GP-independent receptors. This GP-independent entry mechanism should effectively mediate the entry of all enveloped viruses, yet LASV GP-pseudotyped viruses were previously found to be unresponsive to PtdSer receptor enhancement in HEK 293T cells. Here, we demonstrate that LASV pseudovirions can utilize the PtdSer receptor TIM-1 but only in the absence of appropriately glycosylated α-dystroglycan (αDG), the high-affinity cell surface receptor for LASV. Our studies shed light on LASV receptor utilization and explain why previous studies performed with α-DG-expressing cells did not find that LASV pseudovirions utilize PtdSer receptors for virus uptake.

Inhibition of T cell immunoglobulin and mucin-1 (TIM-1) protects against cerebral ischemia-reperfusion injury.

BACKGROUND: The T cell Ig domain and mucin domain (TIM)-1 protein expressed on the surface of Th2 cells regulates the immune response by modulating cytokine production. The present study aimed to investigate the role and possible mechanism of TIM-1 in cerebral ischemia-reperfusion injury. METHODS: Western blot was used to detect TIM-1 and apoptosis-related protein expression, whereas TIM-1 mRNA was examined using quantitative real-time reverse transcription PCR. Flow cytometry and a TdT-mediated biotin-16-dUTP nick-end labeling (TUNEL) assay were used to detect the percentage of apoptotic cells and a pathological examination was performed. The migration of neutrophils and macrophages was analyzed by immunohistochemistry. RESULTS: Our results suggest that TIM-1 expression was transiently increased 24 h or 48 h following middle cerebral artery occlusion (MCAO)/reperfusion. The infarct size was markedly increased in MCAO, whereas treatment with a TIM-1-blocking mAb could reduce the infarct size. TIM-1 blocking mAb effectively reduced the number of neutrophils, macrophage functionality, cytokine (i.e., IL-6, IL-1ß, and TNF-α) and chemokine (i.e., CXCL-1 and CXCL-2) production in the brain tissue. The effect of in vitro T cell damage on neurons was significantly reduced following treatment with a TIM-1 blocking mAb or the knockdown of TIM-1 in co-cultured T cells and neurons. CONCLUSION: Take together, these results indicated that TIM-1 blockade ameliorated cerebral ischemia-reperfusion injury. Thus, TIM-1 disruption may serve as a novel target for therapy following MCAO.

In Vitro and In Vivo Renoprotective Effects of Telbivudine in Chronic Hepatitis B Patients Receiving Nucleotide Analogue.

AIM: Renal toxicity of adefovir disoproxil (ADV) and tenofovir disoproxil fumarate (TDF) is a significant concern in chronic hepatitis B (CHB) patients. Early observational clinical data suggested that telbivudine (LdT) might have renoprotective effects. METHODS: In this prospective study, consecutive CHB patients on combined lamivudine (LAM) + ADV/TDF were switched to LdT + ADV/TDF at recruitment and were followed up for 24 months. Estimated glomerular filtration rate (eGFR) was calculated with the modification of diet in renal disease equation. The effects of LdT on cell viability and expression of kidney injury or apoptotic biomarkers were investigated in cultured renal tubular epithelial cell line HK-2. RESULTS: Thirty-one patients (median age 55 years, 90.3% male) were recruited (54.8% TDF: 45.2% ADV). Serum HBV DNA was undetectable at all time points. Median eGFR was 70.2 (IQR 62.6-77.9) and 81.5 (IQR 63.6-99.1) mL/min/1.73 m2 at baseline and 24 months, respectively (p < 0.001). Downstaging of chronic kidney disease was observed in eight (25.8%) patients and was more common in ADV-treated compared to TDF-treated patients (7/8 vs. 1/17, p = 0.011; OR 16, 95% CI 1.643-155.766, p = 0.017). In vitro data showed that adding LdT to ADV or TDF was associated with improved cell viability and lower expression of injury and apoptotic biomarkers compared with ADV or TDF alone. Treatment was prematurely discontinued in four(12.9%) patients due to myalgia. CONCLUSIONS: Clinical and in vitro data suggest that LdT has renoprotective effects in patients on long-term ADV/TDF treatment. LdT may be considered as an adjuvant therapy in this special group of patients with renal impairment (NCT03778567).