NOS inhibitors modulate LPS-induced gastric MMP and TIMP production

Abstract

Introduction. Matrix metalloproteinases (MMPs) are zinc-endopeptidases that are closely modulated by their endogenous inhibitors, the tissue inhibitors of metalloproteinases, or TIMPs. We have previously demonstrated that lipopolysaccharide (LPS) induces gastric MMPs and that these MMPs contribute to LPS-induced gastric injury. Prior studies in our laboratory have also shown that LPS increases gastric inducible nitric oxide synthase (iNOS), the inhibition of which ameliorated LPS induced gastric injury. While nitric oxide has been shown to modulate MMP production in cell lines, the effect of NOS inhibition on LPS-induced gastric MMP production is unknown. The purpose of these studies was to determine what effects selective and nonselective NOS inhibition had on LPS-induced gastric MMP and TIMP production. Methods. Sprague-Dawley rats were treated with L-NAME (5 mg/kg sc), a nonselective NOS inhibitor, 1400w (1 mg/kg ip), a selective iNOS inhibitor, or vehicle followed by saline or LPS (20 mg/kg ip). After 24 h the rats were sacrificed and the gastric mucosa was harvested for protein and RNA extraction. MMP-2, MMP-9, TIMP-1, and TIMP-2 production were assessed by Western analysis and quantitative real-time RT-PCR. Results. Both L-NAME and 1400w blocked the LPS induced TIMP-1 transcription and protein production. While both agents markedly decreased LPS-induced MMP-9 transcription, no MMP-9 protein was detected in the gastric mucosa. Neither agent had any effect on MMP-2 or TIMP-2 transcription nor did they inhibit the LPS-induced increase in MMP-2 protein. L-NAME had no effect, while 1400w induced TIMP-2 protein; however, the fold increase in TIMP-2 was not as great as for MMP-2, favoring continued matrix degradation. Conclusions. Both constitutive and selective NOS inhibitors modulate gastric MMP and TIMP transcription and protein production. However, neither agent appears to significantly affect the predominant active gelatinase, MMP-2.