Activin/follistatin in mouse lymphocytes

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We have demonstrated that activin is an autocrine regulator of matrix metalloproteinase (MMP) -2 production in mouse peritoneal macrophages. Although the expression of βA subunit and follistatin was detected, that of α and βB subunit was not found in macrophages by reverse transcription-polymerase chain reaction (RT-PCR), suggesting that macrophages produce activin (activin A) and its binding protein, follistatin, but not inhibin. LPS, a potent inflammatory stimulus, stimulated the production of activin βA subunit mRNA and activin activity from mactophages. LPS-stimulated activin production from macrophages was not affected by IFN-γ. The expression of both type I and type II activin receptors in mouse peritoneal macrophages suggests that activin produced by macrophages acts as an autocrine regulator of macrophage function. Gelatin zymography analysis revealed that the production of MMP-2 from macrophages was enhanced by activin. Exogenously added follistatin suppressed MMP-2 activity f … More rom macrophages, indicating that MMP-2 is regulated, at laeast in part, by endogenous activin in an autocrine manner. MMP-2 activity was regulated by activin and follistatin at a mRNA level as revealed by competitive RT-PCR. Neither activin nor follistatin affected the production of mRNA or the activity of MMP-9 from macrophages. Since MMP-2 constitutes the key and rate-limiting proteinase governing the degradation of basement membrane collagens, activin may have a role in migration and infiltration of macrophages through the basement membrane in an inflammatory state.Activin is a potent cell growth and differentiation factor in many biological systems. However, expression and function of activin in the immune system are so far unknown. Here we demonstrated mRNA expression of activin βA, the binding protein (follistatin), and the receptors in B lymphocytes. In addition, we also show the dynamic changes in mRNA expression of activin, follistatin and activin receptors in response to activation of B lymphocytes to exert activin's action. Activin βA mRNA level was increased in the cultured B lymphocytes by LPS, whereas follistatin mRNA was decreased. Consistent with changes in mRNA level, net activin activity in the culture supernatant of B lymphocytes was also increased by LPS. Furthermore, immunization of mice with ovalbumin resulted in the increased activin βA mRNA and decreased follistatin mRNA in B lymphocytes, suggesting regulation of activin activity in B lymphocytes not only in vitro but also in vivo. The LPS stimulation and the immunization resulted in decreases in mRNAs expression of all four and three activin receptors except for ActRI, respectively. Our findings indicate that B lymphocytes produce activin and are target for activin, which might be the possible role of activin as an autocrine regulator of B lymphocytes. Less