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Open Access Highly Accessed Research article

Inhibition of p38 mitogen-activated protein kinase enhances c-Jun N-terminal kinase activity: Implication in inducible nitric oxide synthase expression

Aleksi Lahti, Outi Sareila, Hannu Kankaanranta and Eeva Moilanen*

Author Affiliations

The Immunopharmacology Research Group, Medical School, University of Tampere and Tampere University Hospital, Tampere, Finland

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BMC Pharmacology 2006, 6:5  doi:10.1186/1471-2210-6-5

Published: 21 February 2006



Nitric oxide (NO) is an inflammatory mediator, which acts as a cytotoxic agent and modulates immune responses and inflammation. p38 mitogen-activated protein kinase (MAPK) signal transduction pathway is activated by chemical and physical stress and regulates immune responses. Previous studies have shown that p38 MAPK pathway regulates NO production induced by inflammatory stimuli. The aim of the present study was to investigate the mechanisms involved in the regulation of inducible NO synthesis by p38 MAPK pathway.


p38 MAPK inhibitors SB203580 and SB220025 stimulated lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) expression and NO production in J774.2 murine macrophages. Increased iNOS mRNA expression was associated with reduced degradation of iNOS mRNA. Treatment with SB220025 increased also LPS-induced c-Jun N-terminal kinase (JNK) activity. Interestingly, JNK inhibitor SP600125 reversed the effect of SB220025 on LPS-induced iNOS mRNA expression and NO production.


The results suggest that inhibition of p38 MAPK by SB220025 results in increased JNK activity, which leads to stabilisation of iNOS mRNA, to enhanced iNOS expression and to increased NO production.