Different effects of a macrophage cytokine on proliferation in astrocytes and Schwann cells

The proliferative response in vitro to a novel macrophage inflammatory protein (MIP) 1 alpha has been investigated in astrocytes and Schwann cells. MIP 1 alpha is growth-inhibitory in all cell systems investigated so far and we show here that this cytokine also inhibits the proliferation of astrocytes. This response is seen most clearly when MIP 1 alpha reduces the proliferative response of astrocytes to a potent mitogen. Elevation of intracellular cyclic AMP with forskolin enhances the effects of MIP 1 alpha. In contrast, we show that the proliferation of cultured Schwann cells is stimulated by MIP 1 alpha, and that stimulation is enhanced by simultaneous exposure to forskolin. The possible consequences of these differing responses are discussed in the context of the acute response to injury and potential for regeneration of the peripheral and central nervous systems.