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NO and NOS isoforms in the development of apoptosis in renal ischemia/reperfusion
Jose Luis Viñas1, Anna Sola, Meritxell Genescà
1Department of Experimental Pathology, IIBB-CSIC, IDIBAPS, Barcelona 08036, Spain.
Abstract:
Nitric oxide (NO) and the expression of endothelial (eNOS) and inducible (iNOS) isoforms of nitric oxide synthase (NOS) are recognized as important mediators of physiological and pathological processes of renal ischemia/reperfusion (I/R) injury, but little is known about their role in apoptosis. The ability of the eNOS/NO system to regulate the iNOS/NO system and thus promote apoptosis was assessed during experimental renal I/R. Renal caspase-3 activity and the number of TUNEL-positive cells increased with I/R, but decreased when NOS/NO systems were blocked with L-NIO (eNOS), 1400W (iNOS), and N-nitro-l-arginine methyl ester (L-NAME; a nonselective NOS inhibitor). I/R increased renal eNOS and iNOS expression as well as NO production. The NO increase was eNOS- and iNOS-dependent. Blockage of NOS/NO systems with L-NIO or L-NAME also resulted in a lower renal expression of iNOS and iNOS mRNA; in contrast, eNOS expression was not affected by iNOS-specific blockage. In conclusion, two pathways define the role of NOS/NO systems in the development of apoptosis during experimental renal I/R: a direct route, through eNOS overexpression and NO production, and an indirect route, through expression/activation of the iNOS/NO system, induced by eNOS.
Insights
Nitric oxide (NO) plays a dual role in kidney injury. Endothelial nitric oxide synthase (eNOS) directly promotes apoptosis, while also activating inducible nitric oxide synthase (iNOS) to further enhance cell death during renal ischemia/reperfusion.
Area of Science:
- Nephrology
- Molecular Biology
- Cellular Physiology
Background:
- Renal ischemia/reperfusion (I/R) injury involves complex physiological and pathological processes.
- Nitric oxide (NO) and its synthase isoforms (eNOS, iNOS) are implicated, but their specific roles in I/R-induced apoptosis remain unclear.
Purpose of the Study:
- To investigate the role of endothelial (eNOS) and inducible (iNOS) nitric oxide synthase pathways in apoptosis during experimental renal I/R.
- To determine if the eNOS/NO system regulates the iNOS/NO system in the context of renal I/R injury.
Main Methods:
- Experimental renal ischemia/reperfusion (I/R) model in rodents.
- Pharmacological inhibition of eNOS (L-NIO), iNOS (1400W), and nonselective NOS (L-NAME).
- Assays for caspase-3 activity, TUNEL staining, and Western blot analysis for eNOS and iNOS expression and mRNA levels.
Main Results:
- Renal I/R increased caspase-3 activity and TUNEL-positive cells, indicating apoptosis.
- NOS inhibition (L-NIO, 1400W, L-NAME) significantly reduced I/R-induced apoptosis.
- I/R elevated renal eNOS and iNOS expression and NO production, dependent on both isoforms.
- Inhibition of eNOS or nonselective NOS reduced iNOS expression and mRNA, while iNOS inhibition did not affect eNOS levels.
Conclusions:
- Two distinct pathways involving NOS/NO systems contribute to apoptosis in renal I/R injury.
- A direct pathway involves eNOS overexpression and subsequent NO production.
- An indirect pathway involves eNOS-induced upregulation of the iNOS/NO system, further promoting apoptosis.
