Interleukin-6-type cytokines in neuroprotection and neuromodulation: Oncostatin M, but not leukemia inhibitory factor, requires neuronal adenosine A₁ receptor function

Neuroprotection is one of the prominent functions of the interleukin (IL)-6-type cytokine family, for which the underlying mechanism(s) are not fully understood. We have previously shown that neuroprotection and neuromodulation mediated by IL-6 require neuronal adenosine A₁ receptor (A ₁R) function. We now have investigated whether two other IL-6-type cytokines [oncostatin M (OSM) and leukemia inhibitory factor (LIF)] use a similar mechanism. It is presented here that OSM but not LIF, enhanced the expression of A₁Rs (both mRNA and protein levels) in cultured neurons. Whereas the neuroprotective effect of LIF was unchanged in A ₁R deficient neurons, OSM failed to protect neurons in the absence of A₁R. In addition, OSM pre-treatment for 4 h potentiated the A ₁R-mediated inhibition of electrically evoked excitatory post-synaptic currents recorded from hippocampal slices either under normal or hypoxic conditions. No such effect was observed after LIF pre-treatment. Our findings thus strongly suggest that, despite known structural and functional similarities, OSM and LIF use different mechanisms to achieve neuroprotection and neuromodulation.