Extracellular matrix metalloproteinase inducer is expressed in the proximal tubular epithelial cells of the human kidney

Cyclophilin A/CD147 signaling induces the epithelial-to-mesenchymal transition and renal fibrosis in chronic allograft dysfunction by regulating p38 MAPK signaling

Objective

Our study was designed to explore the role of Cyclophilin A (CyPA)/CD147 signaling in renal allograft fibrosis and chronic allograft dysfunction (CAD).

Materials and methods

A rat renal transplant model with significant CAD was successfully achieved. Renal allograft tissues and blood samples were collected. Hematoxylin and eosin, Masson’s, and immunohistochemistry staining were performed. Since CD147 is mainly expressed in the renal tubular epithelial cells, human HK-2 cells were used and intervened by specific concentrations of CyPA, and the total protein and mRNA were extracted. Western blot assay and polymerase chain reaction were performed to explore the protein and mRNA expression of CyPA, CD147, and epithelial-to-mesenchymal transition (EMT)-related biomarkers. SiRNA-CD147 and specific inhibitors of p38 MAPK were used to explore the cellular mechanisms involved in the process.

Results

We have successfully established and validated a 20-week renal transplant CAD model. We observed significant distributed and expressed CyPA and CD147 in the renal allograft fibrotic tissues. We also found a significant expression of CD147 and EMT-related markers in the HK-2 cells stimulated by CyPA. The CD147 siRNA confirmed the previous in vitro results. The selective inhibition of MAPK suggested the notable role of p38 MAPK signaling pathway in the CyP/CD147 signaling involved in renal allograft fibrosis.

Conclusions

Our study reported the positive relationship of CyPA-CD147 signaling with renal allograft dysfunction. The in vitro study suggested that CyPA-CD147 signaling induce the development of the EMT process by p38 MAPK signaling, thus contributing to renal allograft fibrosis and CAD.

Matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in kidney disease

Matrix metalloproteinases (MMPs) are a group of zinc and calcium endopeptidases which cleave extracellular matrix (ECM) proteins. They are also involved in the degradation of cell surface components and regulate multiple cellular processes, cell to cell interactions, cell proliferation, and cell signaling pathways. MMPs function in close interaction with the endogenous tissue inhibitors of matrix metalloproteinases (TIMPs), both of which regulate cell turnover, modulate various growth factors, and participate in the progression of tissue fibrosis and apoptosis. The multiple roles of MMPs and TIMPs are continuously elucidated in kidney development and repair, as well as in a number of kidney diseases. This chapter focuses on the current findings of the significance of MMPs and TIMPs in a wide range of kidney diseases, whether they result from kidney tissue changes, hemodynamic alterations, tubular epithelial cell apoptosis, inflammation, or fibrosis. In addition, the potential use of these endopeptidases as biomarkers of renal dysfunction and as targets for therapeutic interventions to attenuate kidney disease are also explored in this review.

Evidence For and Against Direct Kidney Infection by SARS-CoV-2 in Patients with COVID-19

Despite evidence of multiorgan tropism of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in patients with coronavirus disease 2019 (COVID-19), direct viral kidney invasion has been difficult to demonstrate. The question of whether SARS-CoV2 can directly infect the kidney is relevant to the understanding of pathogenesis of AKI and collapsing glomerulopathy in patients with COVID-19. Methodologies to document SARS-CoV-2 infection that have been used include immunohistochemistry, immunofluorescence, RT-PCR, in situ hybridization, and electron microscopy. In our review of studies to date, we found that SARS-CoV-2 in the kidneys of patients with COVID-19 was detected in 18 of 94 (19%) by immunohistochemistry, 71 of 144 (49%) by RT-PCR, and 11 of 84 (13%) by in situ hybridization. In a smaller number of patients with COVID-19 examined by immunofluorescence, SARS-CoV-2 was detected in 10 of 13 (77%). In total, in kidneys from 102 of 235 patients (43%), the presence of SARS-CoV-2 was suggested by at least one of the methods used. Despite these positive findings, caution is needed because many other studies have been negative for SARS-CoV-2 and it should be noted that when detected, it was only in kidneys obtained at autopsy. There is a clear need for studies from kidney biopsies, including those performed at early stages of the COVID-19-associated kidney disease. Development of tests to detect kidney viral infection in urine samples would be more practical as a noninvasive way to evaluate SARS-CoV-2 infection during the evolution of COVID-19-associated kidney disease.

The roles of CD147 and/or cyclophilin A in kidney diseases

CD147 is a widely expressed integral plasma membrane glycoprotein and has been involved in a variety of physiological and pathological activities in combination with different partners, including cyclophilins, caveolin-1, monocarboxylate transporters, and integrins. Recent data demonstrate that both CyPA and CD147 significantly contribute to renal inflammation, acute kidney injury, renal fibrosis, and renal cell carcinoma. Here we review the current understanding of cyclophilin A and CD147 expression and functions in kidney diseases and potential implications for treatment of kidney diseases.

CD147 renal expression as a biomarker for progressive IgAN

BACKGROUND/AIMS

Recent studies have demonstrated that tubulointerstitial injury can predict renal outcomes better than the other histological parameters in patients with IgA nephropathy (IgAN). CD147 is a key regulator of renal tubulointerstitial fibrosis in cellular and animal models. However, it is not clear whether the expression of CD147 correlates with tubulointerstitial injury in IgAN patients.

METHODS

We analyzed the degree of CD147 expression and localization in renal biopsy tissues from IgAN patients and correlated their immunostaining scores with clinical and histological parameters.

RESULTS

Elevated CD147 expression was found in the basolateral membrane of renal tubules in IgAN patients; however, in normal kidney samples, positive staining for CD147 was not found in the tubular epithelial cells (P = 0.000). CD147 protein expression in the renal tubules showed a negative correlation with estimated glomerular filtration rate (eGFR; r = -0.600, P = 0.000) and a positive correlation with serum creatinine (Scr; r = 0.322, P = 0.002) and tubulointerstitial lesions (r = 0.525, P = 0.000). Moreover, a high level of CD147 correlated with the activation of Slug expression and E-cadherin repression in patients with IgAN. Kaplan-Meier survival curves showed that elevated CD147 expression was associated with decreased renal survival. Multivariate analyses further demonstrated that a high CD147 immunostaining score was an independent predictor of renal outcome in patients with IgAN (HR = 8.731, P = 0.041).

CONCLUSION

CD147 expression is associated with tubulointerstitial injury and predicts renal prognosis in IgA nephropathy. CD147 may be an early marker for tubulointerstitial injury IgA nephropathy.

Renal cell neoplasias: reversion-inducing cysteine-rich protein with Kazal motifs discriminates tumor subtypes, while extracellular matrix metalloproteinase inducer indicates prognosis

Background

Matrix metalloproteinases can promote invasion and metastasis, which are very frequent in renal cell carcinoma even at the time of diagnosis. Knowing the reversion-inducing cysteine-rich protein with Kazal motifs (RECK) as an inhibitor of matrix metalloproteinases and the extracellular matrix metalloproteinase inducer (EMMPRIN) protein as inducer, we aimed to determine their expression, localization and possible antagonistic action in the pathogenesis and progression of renal cell tumors in a retrospective study.

Methods

Tumor and adjacent normal tissues of 395 nephrectomized patients were immunostained for RECK and EMMPRIN on a tissue microarray.

Results

RECK strongly decreased in renal cell carcinoma compared to normal counterparts (Wilcoxon signed rank test, P < 0.001), and it discriminated tumor entities showing the highest expression in oncocytomas. EMMPRIN, however, could be significantly correlated to pT stage and Fuhrman grading (Spearman’s correlation coefficient r_s = 0.289 and r_s = 0.382, respectively). Higher expression of EMMPRIN was associated with decreased overall survival in Kaplan-Meier analysis (P < 0.001), and the EMMPRIN level could independently predict survival for cases without metastasis and involvement of lymph nodes. Decreased RECK expression was confirmed by Western blotting in tissue of eight normal/tumor matches of patients after radical nephrectomy, whereas the EMMPRIN pattern appeared to be heterogeneous.

Conclusions

We propose RECK down regulation in renal cell carcinoma to be an early event that facilitates tumor formation and progression. EMMPRIN, however, as a prognostic tumor marker, increases only when aggressiveness is proceeding and could add an additional step to invasive properties of renal cell carcinoma.

Expression of basigin in the early phase of acute myocardial ischemia in rats

Basigin may be involved in cardiovascular disease. In our previous study, suppression subtractive hybridization results indicated that basigin may be associated with the early phase of acute myocardial ischemia (AMI) within 1 h. However, little is known regarding the expression of basigin in the early phase of AMI. The aim of the present study was to evaluate the temporal and spatial expression patterns of basigin mRNA and protein levels in AMI in rats. We constructed an AMI model in rats that received left anterior descending coronary artery ligation for 0, 15, 30, 60, 120 or 240 min. Real‑time quantitative PCR and in situ hybridization (ISH) were conducted to reveal the basigin mRNA levels in the early ischemic myocardium (EIM) and non‑ischemic myocardium (NIM). The expression levels of basigin protein were detected using western blot analysis and immunohistochemistry. The expression levels of basigin mRNA and protein significantly changed in the EIM as early as 30 min from ischemia, and the changes continued to be present throughout the ischemic period (P<0.05). The expression levels of basigin mRNA were significantly reduced, whilst those of the protein underwent a significant ~2-fold increase in the EIM. However, there were no significant differences in the basigin mRNA or protein expression levels from 0‑240 min in the NIM (P>0.05). We failed to detect a signal for basigin mRNA in the myocardium by ISH. Our findings indicated that basigin may be involved in acute myocardial ischemia following continual ischemia for >30 min.

Resveratrol blocks interleukin-18-EMMPRIN cross-regulation and smooth muscle cell migration

Vascular smooth muscle cell (SMC) migration is an important mechanism in atherogenesis and postangioplasty arterial remodeling. Previously, we demonstrated that the proinflammatory cytokine interleukin (IL)-18 is a potent inducer of SMC migration. Since extracellular matrix metalloproteinase inducer (EMMPRIN) stimulates ECM degradation and facilitates cell migration, we investigated whether IL-18 and EMMPRIN regulate each other's expression, whether their cross talk induces SMC migration, and whether the phytoalexin resveratrol inhibits IL-18-EMMPRIN signaling and SMC migration. Our studies demonstrate that 1) IL-18 induces EMMPRIN mRNA and protein expressions and stimulates EMMPRIN secretion from human aortic SMCs; 2) IL-18 stimulates EMMPRIN expression via oxidative stress and phosphatidylinositol 3-kinase (PI3K)-Akt-ERK signaling; 3) IL-18-stimulated SMC migration is significantly blunted by EMMPRIN knockdown, EMMPRIN function-blocking antibodies, or adenoviral transduction of mutant EMMPRIN; 4) conversely, EMMPRIN stimulates IL-18 expression and secretion via PI3K, Akt, and ERK; and 5) resveratrol attenuates IL-18- and EMMPRIN-mediated PI3K, Akt, and ERK activations; blunts IL-18-mediated oxidative stress; blocks IL-18-EMMPRIN cross-regulation; and inhibits SMC migration. Collectively, our results demonstrate that the coexpression and regulation of IL-18 and EMMPRIN in the vessel wall may amplify the inflammatory cascade and promote atherosclerosis and remodeling. Resveratrol, via its antioxidant and anti-inflammatory properties, has the potential to inhibit the progression of atherosclerosis by blocking IL-18 and EMMPRIN cross-regulation and SMC migration.