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Gentamicin induces Jun-AP1 expression and JNK activation in renal glomeruli and cultured mesangial cells
Carlos Martínez-Salgado1, Alicia Rodríguez-Barbero, Nélida Eleno
1Unidad de Investigación, Hospital Universitario de Salamanca, Paseo de San Vicente 58-132, 37007 Salamanca, Spain. carlosms@usal.es
Abstract:
Reactive oxygen species (ROS) mediate MC contraction, proliferation and apoptosis induced by gentamicin (G) in vitro and in vivo. Sustained increases in cytosolic free calcium, increased iNOS expression and elevated nitric oxide (NO) production are associated with MC apoptosis in vitro. As NO strongly activated c-Jun N-terminal kinase (JNK) and increased AP1 expression, and these two factors are involved in MC proliferation in vitro, we have measured Jun-AP1 expression in rat glomeruli from G-treated rats, and the effect of G on Jun-AP1 expression and JNK activity in cultured MC. Moreover, we studied the expression of inducible (iNOS) and constitutive (cNOS) NO synthases in rat glomeruli. Glomeruli were obtained from rats treated with G (100 mg/kg body weight/day) along 6 days, and MC primary cultures were evaluated after 24, 48 and 72 h incubation with 10(-5) M G. G induced an increase in the expression of iNOS, cNOS and Jun-AP1 in rat glomeruli and in MC cultures. Moreover, G activated JNK; JNK activation was reduced by co-incubation with the calcium channel blocker verapamil and with the ROS scavengers superoxide dismutase and catalase. These results strongly suggest a role for reactive oxygen/nitrogen species produced by increased NOS activity in G-induced MC activation. These reactive oxygen molecules and increased intracellular free calcium may mediate the increase in Jun-AP1 expression and JNK activation induced by G treatment in MC.
Insights
Gentamicin induces mesangial cell (MC) damage via reactive oxygen species (ROS) and nitric oxide (NO) production. Increased NO and ROS, along with calcium, activate JNK and Jun-AP1, suggesting a pathway for gentamicin-induced MC injury.
Area of Science:
- Nephrology
- Cell Biology
- Toxicology
Background:
- Gentamicin (G) induces mesangial cell (MC) dysfunction, involving reactive oxygen species (ROS).
- Nitric oxide (NO) production and calcium signaling are implicated in MC apoptosis and proliferation.
- c-Jun N-terminal kinase (JNK) and AP1 are key regulators of MC proliferation.
Purpose of the Study:
- To investigate the role of ROS and NO in gentamicin-induced MC activation.
- To examine the effect of gentamicin on JNK activity and Jun-AP1 expression in MC.
- To explore the involvement of inducible (iNOS) and constitutive (cNOS) nitric oxide synthases in gentamicin nephrotoxicity.
Main Methods:
- Rats were treated with gentamicin (100 mg/kg/day for 6 days).
- Primary MC cultures were incubated with gentamicin (10(-5) M) for 24, 48, and 72 hours.
- Expression of iNOS, cNOS, and Jun-AP1 was measured in glomeruli and MC cultures.
- JNK activity was assessed in MC cultures, with and without verapamil or ROS scavengers (superoxide dismutase, catalase).
Main Results:
- Gentamicin increased iNOS, cNOS, and Jun-AP1 expression in rat glomeruli and MC cultures.
- Gentamicin activated JNK in MC cultures.
- JNK activation was attenuated by verapamil, superoxide dismutase, and catalase.
- Increased intracellular calcium correlated with JNK activation and Jun-AP1 expression.
Conclusions:
- Gentamicin-induced MC activation is mediated by reactive oxygen/nitrogen species generated by increased NOS activity.
- Increased intracellular calcium and ROS contribute to JNK activation and Jun-AP1 expression.
- These findings elucidate a mechanism of gentamicin nephrotoxicity involving oxidative stress and signaling pathways.
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