TRPV1功能亢進促成大鼠高草酸腎臟中炎症與草酸鈣結晶形成
馬明傑 ¹、黃鶴翔 ²
輔仁大學醫學系 ¹、國立成功大學附設醫院泌尿科 ²
TRPV1 hyperfunction contributes to inflammation and CaOx crystal formation in the rat hyperoxaluric kidney
Ming-Chieh Ma1, Ho-Shiang Huang2
School of Medicine1, Fu Jen Catholic University, New Taipei, Taiwan; Department of Urology2, National Cheng Kung University, Tainan, Taiwan

 

Purpose: Inflammation worsens oxalate nephropathy by exacerbating tubular cell damage and leading to end-stage renal failure. Transient receptor potential vanilloid channel 1 (TRPV1) is present in the kidney with polymodal detecting ability. Here we tested whether TRPV1 may contribute to hyperoxaluria-induced inflammation and calcium oxalate (CaOx) crystal formation via its sensing function.

 

Materials and Methods: Rat proximal tubular cells were isolated and prepared as the primary resource for in vitro study. Fluo-3 AM was given cells to monitor changes in intracellular calcium levels ([Ca2+]i). Cells and culture medium were collected to examine protein expression of interested after treatment of TRPV1 inhibitor or in combination with oxalate. For in vivo study, chronic hyperoxaluria was induced in the Male Wistar rats fed with 5% hydroxyl-L-proline (HP) in daily diet for 28 days. The 24-h urine was collected for urinalysis. Subcutaneous implant of mini-osmotic pumps were prepared for chronic drug delivery of specific TRPV1 blocker.

 

Results: Oxalate induced cell damage and [Ca2+]i elevation in primary proximal tubular cells; those could be mitigated by TRPV1 inhibition. Oxalate mediated protein kinase C a and NAD(P)H oxidase activation for generating oxygen radicals were partially attenuated by TRPV1 inhibition. These associated with reductions of inflammasome NLRP3 upregulation, caspase-1 activation, and interleukin (IL)-1β release after oxalate treatment. These in vitro evidences clearly indicate that TRPV1 acts as an oxalate sensor for triggering tubular damage in inflammation. HP induced hyperoxaluria, urinary supersaturation, and tubular damage after 3 days of induction when compared with controls. These were associated with increases in renal TRPV1 and NLRP3 expression, caspase-1 activity, and IL-1β content as peak changes on day 14. Chronic TRPV1 inhibition by capsazepine or SB336791 via subcutaneous implant of mini-osmotic pumps did not affect hyperoxaluria and degree of urinary supersaturation, but markedly attenuated tubular injury and CaOx crystal formation. TRPV1 inhibition also attenuated HP-induced NLRP3 upregulation and increases in caspase-1 activity and IL-1β levels.

 

Conclusion: Our results indicate that TRPV1 hyperfunction contributes to CaOx crystal formation in the hyperoxaluric kidneys. Blunting sensing ability of TRPV1 attenuates hyperoxaluria-mediated