Mechanisms of suppression of macrophage nitric oxide release by transforming growth factor beta.

Abstract

SummaryActivated mouse peritoneal macrophages produce nitric oxide (NO) via a nitric oxide synthase that is inducible by interferon 3, (IFN-7): iNOS. We have studied the mechanisms by which transforming growth factor ~1 (TGF-~) suppresses IFN-7-stimulated NO production. TGF-~/ treatment reduced iNOS specific activity and iNOS protein in both cytosolic and particulate fractions as assessed by Western blot with monospecific anti-iNOS immunoglobulin G. TGF-~ reduced iNOS mRNA without affecting the transcription ofiNOS by decreasing iNOS mRNA stability. Even after iNOS was already expressed, TGF-~ reduced the amount of iNOS protein.This was due to reduction ofiNOS mRNA translation and increased degradation ofiNOS protein.The potency of TGF-B as a deactivator of NO production (50% inhibitory concentration, 5.6 _+ 2 pM) may reflect its ability to suppress iNOS expression by three distinct mechanisms: decreased stability and translation of iNOS mRNA, and increased degradation of iNOS protein. This is the first evidence that iNOS is subject to other than transcriptional regulation. ecent appreciation of the role of endogenously generated nitric oxide (NO) 2 in the physiology and pathophysiology of every organ system raises interest in mechanisms by which NO production may be regulated (1). This question assumes additional significance in view of the ability of NO to kill or damage cells (2).Constitutive isoforms of NO synthase (chiOS) are expressed in neurons and endothelium. These enzymes produce small amounts of NO over several minutes in response to agonists that elevate intracellular Ca 2 + (1). press an inducible isoform of NO synthase (iNOS) that produces relatively large amounts of NO over many hours without dependence on secretagogues. Nothing is known to regulate iNOS after it has been induced (1).Suppression of iNOS expression was first shown in macrophages exposed to TGF-B (16). These results were confirmed 1 Yoram Vodovotz and Christian Bogdan contributed equally to the e~periments described in this work.2 Abbreviations used in this paper: cNOS, constitutive isoforms of nitric oxide synthase; FAD, ravin adenine dinucleotide; GAPDH, glyr.eraldehyde-3-phosphate dehydrogenase; iNOS, inducible isoform of nitric oxide synthase; NADPH, 3-nicotinamide-adenine dinucleotide phosphate; NO, nitric oxide.

PPARα agonists inhibit nitric oxide production by enhancing iNOS degradation in LPS‐treated macrophages

“…TGF-b, in addition to its effects on iNOS mRNA stability and translation, has been found to increase degradation of iNOS protein in macrophages (Vodovotz et al, 1993;Mitani et al, 2005) and in chondrocytes (Vuolteenaho et al, 2005). In addition, dexamethasone has been reported to decrease iNOS protein stability in IL-1-stimulated mesangial cells (Kunz et al, 1996).…”

M-1/M-2 Macrophages and the Th1/Th2 Paradigm

“…To probe the molecular basis for these differences, TGF-␤1 production by M-1 and M-2 macrophages was measured. TGF-␤1 was selected for study because it is known to be a powerful inhibitor of macrophage NO production (45,46). In addition, TGF-␤1 has been reported to increase arginase activity (47).…”

Regression of AK7 malignant mesothelioma established in immunocompetent mice following intratumoral gene transfer of interferon gamma

“…TGF-b may favor tumorigenesis through a number of mechanisms such as blocking activation of macrophages via inhibition of TNF-a production, or by decreasing expression of MHC class II 27 or suppressing IFN-g-stimulated NO production via nitric oxide synthase. 28 Fitzpatrick et al 26 demonstrated that the suppression of TGF-b secretion using antisense constructs led to the enhancement of tumor infiltration by T lymphocytes.…”