We have been proposing the functional discrimination of two classes of macrophages (Mp), i.e. reductive macrophages (RMp) with a high intracellular content of glutathione and oxidative macrophages (OMp) with a reduced content. In this paper we will present the evidence that the T(h)1/T(h)2 balance is regulated by the balance between RMp and OMp due to the disparate production of IL-12 versus IL-6 and IL-10. RMp were induced by in vivo application of N-acetyl-L-cysteine or glutathione monoethylester and OMp by L-cystine derivatives, diethyl maleate or L-buthionine-[S,R]-sulfoximine. The Mp arbitrarily called OMp showed elevated IL-6 and IL-10 production, and reduced NO and IL-12 production. The RMp elicited a reciprocal response, i.e. elevated IL-12 and NO production, and reduced IL-6 and IL-10 production. The cytokine propensities of OMp or RMp were inter-converted to each other. The results were also confirmed by using auto-MACS purified F4/80(+) Mp without adherence. Interestingly, IFN-gamma induced RMp and augmented NO generation with decreased production of IL-6, whilst IL-4 induced OMp and augmented IL-6 production. CD4(+)CD44(-) naive T(h)0 cells were differentiated preferentially either to T(h)l or T(h)2 cells, depending on the presence of RMp or OMp during the initial 24 h of culture, from ovalbumin-specific TCR-transgenic mouse spleen cells in the presence of IL-2. Taken together, RMp induction may generate the amplification loop of a RMp/T(h)1 circuit and OMp that of OMp/T(h)2. The findings implicate that the alteration in Mp functions because altered intracellular glutathione may play a relevant role in the pathological progression of inflammation.

SUMMARYInterleukin-12 (IL-12) is secreted from monocytes and macrophages; it exerts pleiotropic effects on T cells and natural killer (NK) cells, and stimulates interferon-g (IFN-g ) secretion. Glutathione tripeptide regulates the intracellular redox status and other aspects of cell physiology. We examined whether IFNg and IL-4 affect the balance between intracellular reduced glutathione (GSH) and oxidized (GSSG) glutathione, as this may affect IL-12 production in human alveolar macrophages (AM). We used both AM from healthy non-smokers obtained by bronchoalveolar lavage and the monocytic THP-1 cell line in this study. Incubation of AM for 2 h with the GSH precursor N-acetylcysteine (NAC) increased the intracellular GSH/GSSG ratio, and enhanced lipopolysaccharide (LPS)-induced IL-12 secretion by AM. In THP-1 cells, NAC increased the GSH/GSSG ratio and the expression of LPS-induced IL-12 mRNA, whereas l-buthionine-[S,R]-sulphoximine (BSO) decreased these. NAC and BSO offset their own effects on the intracellular GSH/GSSG ratio and the expression of LPS-induced IL-12 mRNA. Furthermore, exposure of AM to the helper T cell type 1 (Th1) cytokine IFN-g or the helper T cell type 2 (Th2) cytokine IL-4 for 72 h increased and decreased the GSH/GSSG ratio, respectively. Lipopolysaccharide (LPS)-induced secretion of IL-12 in AM was enhanced by IFN-g but inhibited by IL-4. These results suggest that IFN-g and IL-4 oppositely affect the GSH/GSSG balance, which may regulate IL-12 secretion from AM in response to LPS.

Although c-Jun N-terminal kinase (JNK) plays an important role in cytokine expression, its function in IL-12 production is obscure. The present study uses human macrophages to examine whether the JNK pathway is required for LPS-induced IL-12 production and defines how JNK is involved in the regulation of IL-12 production by glutathione redox, which is the balance between intracellular reduced (GSH) and oxidized glutathione (GSSG). We found that LPS induced IL-12 p40 protein and mRNA in a time- and concentration-dependent manner in PMA-treated THP-1 macrophages, and that LPS activated JNK and p38 mitogen-activated protein (MAP) kinase, but not extracellular signal-regulated kinase, in PMA-treated THP-1 cells. Inhibition of p38 MAP kinase activation using SB203580 dose dependently repressed LPS-induced IL-12 p40 production, as described. Conversely, inhibition of JNK activation using SP600125 dose dependently enhanced both LPS-induced IL-12 p40 production from THP-1 cells and p70 production from human monocytes. Furthermore, JNK antisense oligonucleotides attenuated cellular levels of JNK protein and LPS-induced JNK activation, but augmented IL-12 p40 protein production and mRNA expression. Finally, the increase in the ratio of GSH/GSSG induced by glutathione reduced form ethyl ester (GSH-OEt) dose dependently enhanced LPS-induced IL-12 p40 production in PMA-treated THP-1 cells. GSH-OEt augmented p38 MAP kinase activation, but suppressed the JNK activation induced by LPS. Our findings indicate that JNK negatively affects LPS-induced IL-12 production from human macrophages, and that glutathione redox regulates LPS-induced IL-12 production through the opposite control of JNK and p38 MAP kinase activation.

No abstract

No abstract