P0421STUDY OF DIFFERENT EXPRESSION PROFILES OF “TRANSIENT RECEPTOR POTENTIAL ION CHANNEL (TRPC) GENE FAMILY” IN PATIENTS UNDERGOING RENAL BIOPSY WITH CLINICAL SUSPECTED GLOMERULONEPHRITIS
Authors: Sezis Meltem , Erac Yasemin , Güler Hale , Atay Gökhan , Cenk Demirci , Özkahya Mehmet , Ok Ercan , Şen Sait , Sarsık Kumbaracı Banu , Kosova Buket 
Published: June 2020

Abstract

Background and Aims
The transient receptor potential ion channels (TRPC) are non-selective Ca+ 2 permeable cation channels and are widely expressed in the tissues of vertebrates. They become active in response to signal transduction pathways associated with phospholipase C stimulation. TRPC6 is expressed in podocytes and is a component of the slit diaphragm. In genetic and acquired glomerular kidney diseases, TRPC6 overactivation causes podocyte damage by pathological Ca+ 2 entry. TRPC1, TRPC2, TRPC4, and TRPC5 interact with a protein called stromal-interacting molecule 1 (STIM 1), which is susceptible to intracellular calcium storage content. As a result of binding with this protein, TRPC channels bind to calcium-releasing zone in endosomes. The aim of the study was to investigate different expression profiles of TRPC family members in renal biopsy specimens in patients with clinically considered glomerulonephritis.

Method
This study was conducted with 108 patients admitted to Ege University Faculty of Medicine Nephrology Clinic who underwent a kidney biopsy with a preliminary diagnosis of glomerulonephritis and 37 patients who underwent a nephrectomy in urology clinic with a diagnosis of primary kidney tumour as a control case. PKD2, NPHS2, TRPC1, TRPC3, TRPC6, STIM-1 and Orai-1 mRNA levels were studied in the biopsy samples.

Results
When we compared the patient and the control group, the gender distribution of both groups was similar. The frequency of diabetes and hypertension was similar. The control group was statistically significantly older and glomerular filtration rates were higher than the patient group. In pathological examination, glomerulonephritis (57.5%) was diagnosed in the majority of patients. The most common etiologic factors were membranous nephropathy 23.1%, IgA nephropathy 13%, Amyloidosis 11.2%, focal segmental glomerulosclerosis 7.1%, proliferative glomerulonephritis 4.6%, minimal change disease 2.8% and membranoproliferative glomerulonephritis was 1.9%. 7.4% of the patients were diagnosed with diabetic nephropathy by renal biopsy.
When we compared the TRPC expression profiles of the patient and the control group, the TRPC1, TRPC6, PKD2, NPHS2, STIM-1 and ORAi-1 mRNA levels of the patient group were statistically significantly higher than those of the control group (Figure). In contrast, TRPC3 mRNA levels were significantly lower in the patient group compared to the control group. When we performed subgroup analysis, the TRPC1, TRPC6 and STIM1 levels of the diabetic group were statistically significantly higher compared to the non-diabetic group of patients. We could not find any difference between TRPC expression profiles between the patients according to pathological diagnosis. Similarly, there was no difference between the amount of proteinuria (nephrotic level versus nephritic level). In correlation analysis, there was a negative correlation with TRPC6 and STIM1 levels with positive C4d staining of glomeruli in renal biopsy. Positive correlation was found between ORAI and glomerular sclerosis rate.

Conclusion
As a result, we found that other than TRPC3 mRNA level, other TRPC and related protein channels mRNA levels were statistically significantly increased in proteinuric kidney patients compared to healthy kidney tissue. We did not find a positive relationship between proteinuria severity and TRPC expression profiles. We found that TRPC6 and STIM1 expression levels were increased in diabetic patients, which supports the knowledge that intracellular calcium pathways were activated in podocyte damage. In our study, there were significantly increased STIM1 and ORAi-1 expression levels in proteinuric patients compared to the control group and their increase was closely related to TRPC6. From this we can conclude that these proteins play an important role in proteinuric kidney damage.