Synergy of interleukin-4 and interferon-γ in arginase-1 production in RAW264.7 macrophages.

BACKGROUND: Interferon (IFN)-γ and interleukin (IL)-4 are considered to be important factors to regulate immune responses. Although the effects of IFN-γ or IL-4 on macrophage functions are well established, their cooperative action is not fully understood. OBJECTIVE: Inducible nitric oxide synthase (iNOS) or arginase (Arg)-1 is a representative marker of M1 or M2 macrophages and plays a role in the acceleration or suppression of inflammatory responses. In the present study, we examined the effect of simultaneous treatment with IFN-γ and IL-4 on macrophage expression of iNOS and Arg-1 using the murine macrophage cell line RAW264.7. METHODS: Protein production and mRNA expression of iNOS and Arg-1 were measured using immunoblotting and reverse transcription-polymerase chain reaction. Cell surface expression of CD86 and programmed death ligand (PD-L) 2 was analyzed using flow cytometry. RESULTS: IFN-γ or IL-4 increased iNOS or Arg-1 protein production, respectively. Of note, IL-4 combined with IFN-γ synergistically increased Arg-1 protein production, whereas IL-4 inhibited IFN-γ-induced iNOS production. This phenomenon was consistent with the mRNA levels. In addition, IL-4 combined with IFN-γ synergistically increased cell surface expression of PD-L2, which is involved in T cell suppression, whereas IL-4 completely inhibited IFN-γ-induced expression of CD86, which is responsible for T cell activation. CONCLUSIONS: In the present study, we found the synergy of IFN-γ and IL-4 in Arg-1 and PD-L2 expression. Thus, macrophages highly expressing Arg-1 and PD-L2 may be induced by both IFN-γ and IL-4 at the inflammatory site, and might play a role in the regulation of inflammatory immune responses.

Abnormal Pressure Stress Reduces Interleukin-1ß-Induced Cyclooxygenase-2 Expression in Cultured Rat Vascular Smooth Muscle Cells.

Elevated mechanical stress on blood vessels associated with hypertension has a direct effect on the function of vascular endothelial cells and vascular smooth muscle cells (VSMCs). In the present study, we have identified the effect of pulsatile pressure stress on cyclooxygenase-2 (COX-2) expression induced by interleukin (IL)-1ß in cultured rat VSMCs. VSMCs were isolated from aortic media of Wistar rats and cultured. Pulsatile pressure applied to VSMCs was repeatedly given between either 80 and 160 mmHg, which simulates systolic hypertension, or 80 and 120 mmHg, which simulates normal blood pressure, at a frequency of 4 cycles per min using our original apparatus. Pressure loading that simulates systolic hypertension reduced IL-1ß-induced COX-2 expression. The pressure also inhibited the rapid and transient phosphorylation of extracellular signal-regulated kinase (ERK) induced by IL-1ß. IL-1ß-induced COX-2 expression was significantly inhibited by a specific conventional protein kinase C (PKC) inhibitor. Pressure loading that simulates systolic hypertension also reduced phorbol myristate 13-acetate (PMA) (a PKC activator)-induced COX-2 expression and the rapid and transient phosphorylation of ERK. Pressure loading that simulates normal blood pressure had no effect on IL-1ß- and PMA-induced COX-2 expression. The present study shows that pressure stress between 80 and 160 mmHg, which simulates systolic hypertension reduces IL-1ß-induced COX-2 expression by affecting a mechanism involving PKC and ERK signaling pathways. Downregulation of COX-2 expression in VSMCs by abnormal pressure stress may further worsen local vascular injury associated with hypertension.