In microglia, surface engagement of TLR4 by LPS leads to activation of multiple intracellular pathways in cluding those connected to NF ��B, AP 1, JAKSTAT, and multiple protein kinase selleck inhibitor pathways. Recent studies by Gibson et al, have shown a role for NF ��B in the regulation of P gp in a mouse microglia cell line, BV 2. Interestingly, in this study, LPS at doses of 1 to 500 ngml for 12 hours reduced P gp expression, and function using the fluorescent P gp probe rhodamine 123. In the present study using primary cultures of mouse microglia, 10 ngml LPS decreased saquinavir accumulation significantly at 6 and 24 hours, presumably due to increased saquinavir efflux. The observed decrease in saquinavir accumulation in the mouse cultures was, however, modest compared to primary rat cultures, suggesting potential species diffe rences.

Whether species differences in molecular mechanisms or specific substrate Inhibitors,Modulators,Libraries handling can explain Inhibitors,Modulators,Libraries these discrepancies, remains to be confirmed. Of all the molecular pathways examined in the present study, only inhibition of NF ��B and MEK12 reversed the changes in saquinavir accumulation in microglia following LPS exposure. Given that several Inhibitors,Modulators,Libraries pro inflam matory factors that are known activators of NF ��B were shown to have no effect, these Inhibitors,Modulators,Libraries findings support that NF ��B is necessary, but not sufficient to change saquinavir accumulation. These results are in stark contrast to findings in freshly isolated rat brain capillaries where LPS also initiates acti vation of TLR4, which downstream is connected and ultimately results in increased P glycoprotein protein expression and consequently function in the capillaries.

Inhibitors,Modulators,Libraries This may not be surprising, as the trans porter profile in glial cells is quite different compared to cells of the BBB. Most notably, cultured microglia do not express significant levels of Mrp2, Bcrp or mRNA of any of the important SLC uptake transporters expressed at the BBB. Given the redundant nature of the LPS response in microglia, we cannot rule out the possibility that compensatory pathways mask the effects of inhibition or activation of a single pathway in our cell cultures. Further investigations in vivo using knockdown strategies may be helpful to fully elucidate all the path ways that are involved. In summary, we have demonstrated that exposing microglial cells to LPS decreases cellular accumulation of one representative antiretroviral medication.

The ability of LPS to significantly decrease saquinavir accu mulation was consistent between microglia derived from multiple species, multiple strains within the same species, and multiple cell preparations. Using PSC833, a non immunosuppressive cyclosporine A analog and potent P glycoprotein inhibi tor, the decrease in saquinavir accumulation in cultured microglia was consistent, how to order in part, with an increase in P glycoprotein mediated drug efflux.