Inhibition of nitric oxide synthesis by L-name exacerbates acute lung injury induced by hepatic ischemia-reperfusion.
Hepatic Kupffer cells and pulmonary alveolar macrophages together constitute a macrophage-axis involved in the regulation of regional and systemic inflammatory responses. Systemic inflammatory response syndrome induced by overproduced pro-inflammatory mediators is the major cause of adult respiratory distress syndrome. In the present study, we examined the anti-inflammatory role of nitric oxide (NO) in a rat model of acute lung injury induced by hepatic ischemia-reperfusion (HI/R). The left and median lobes of the liver were subjected to 30 min of ischemia by clamping the relevant branches of hepatic artery and portal vein, followed by a 4-h reperfusion achieved by removal of the vascular clamp. Four groups of animals were studied: sham control + saline; sham control + N(omega)-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg, i.v., 10 min before reperfusion); HI/R + saline; HI/R + L-NAME. Results show that (1) administration of L-NAME to rats subjected to HI/R decreased plasma NO levels; however, the attenuation of NO increased plasma alanine aminotransferase (ALT) activity and superoxide generation in the ischemic lobes of liver, compared to HI/R alone. (2) Inhibition of NO synthesis with L-NAME in rats subjected to HI/R also enhanced systemic inflammatory response as assessed by the increase in the number of circulating leukocytes and levels of plasma tumor necrosis factor-alpha (TNFalpha) and interleukin 1-beta (IL-1beta). (3) The overwhelming systemic inflammatory response induced by administration of L-NAME in rats subjected to HI/R also augmented pulmonary vascular permeability and superoxide generation in the lung tissue. (4) Pulmonary alveolar macrophages isolated from rats subjected to HI/R + L-NAME produced higher levels of TNFalpha and IL-1beta in the supernatant of culture medium than that of rats subjected to HI/R alone. (5) There were no differences between the groups of sham + saline and sham + L-NAME in terms of plasma NO levels and ALT activity, circulating leukocytes, superoxide generation in the liver and lung, lavage protein levels, and TNFalpha and IL-1beta levels in plasma and bronchoalveolar lavage fluid. Our results suggest that inhibition of NO synthesis by L-NAME in rats subjected to HI/R not only augments ischemic liver injury, but also enhances the systemic inflammatory response and exacerbates remote lung injury. The increase in TNFalpha and IL-1beta production by alveolar macrophages may, in part, account for L-NAME-induced enhancement of acute lung injury.
Liu
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Department of Cell Biology, University of Medicine and Dentistry of New Jersey, School of Osteopathic Medicine, Stratford 08084, USA.
Xu
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Hock
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D000410:Alanine Transaminase / Q000097:blood / Q000187:drug effects; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007375:Interleukin-1 / Q000378:metabolism; D007958:Leukocyte Count; D008099:Liver / Q000098:blood supply*; D008168:Lung / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009566:Nitrates / Q000097:blood; D009569:Nitric Oxide / Q000096:biosynthesis*; D009573:Nitrites / Q000097:blood; D011506:Proteins / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D015427:Reperfusion Injury / Q000378:metabolism* / Q000503:physiopathology; D013481:Superoxides / Q000378:metabolism; D018746:Systemic Inflammatory Response Syndrome / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D004791:Enzyme Inhibitors; D007375:Interleukin-1; D009566:Nitrates; D009573:Nitrites; D011506:Proteins; D014409:Tumor Necrosis Factor-alpha; D013481:Superoxides; D009569:Nitric Oxide; D000410:Alanine Transaminase; D019331:NG-Nitroarginine Methyl Ester