Toll-like receptor 4 inhibition by pyridostigmine is associated with a reduction in hypertension and inflammation in rat models of preeclampsia.

Background: Preeclampsia (PE) is marked by hypertension and detrimental sterile inflammatory response. Despite the reported anti-inflammatory effect of pyridostigmine bromide (PYR) in different models, its anti-inflammatory mechanism in PE is unclear. This study assessed whether such an anti-inflammatory effect involves inhibition of placental Toll-like receptor 4 (TLR4) signaling.

Methods: Placental TLR4 expression and its signaling were assessed respectively in PE women and Sprague-Dawley rats with reduced uterine perfusion pressure (RUPP) induced on gestational day14 (GD14). RUPP and lipopolysaccharides (LPS, 5 μg/kg)-induced PE rats were treated with a selective TLR4 signaling inhibitor (TAK-242, 2.5 mg/kg/day). The effect of PYR (20 mg/kg/day) on TLR4 expression and signaling was also assessed in RUPP or LPS-infused rats. On GD19, rats' mean arterial pressure (MAP) and samples were collected and processed. At the cellular level, the effect of acetylcholine (ACh), the indirect by-product of PYR activity, on LPS-stimulated HTR-8/SVneo cells was assessed.

Results: Both PE women and RUPP rats had increased (P  < 0.05) placental TLR4 expression and elevated (P  < 0.05) MAP. Selective inhibition of TLR4 signaling with TAK-242 blunted (P < 0.05) RUPP-elevated MAP. Activation of TLR4 induced PE-like symptoms in dams, which were prevented by TAK-242. PYR reduced (P < 0.05) MAP and downregulated placental TLR4 expression and TLR4/TRAF6/NF-κB signaling-mediated inflammation in RUPP and in response to TLR4 selective activation. ACh inhibited the same signaling pathway in LPS-stimulated HTR-8 in vitro.

Conclusion: Our data support that PYR attenuates placental TLR4 expression and inhibits TLR4/TRAF6/NF-κB signaling pathway-mediated inflammation in RUPP, clarifying the anti-inflammatory mechanisms of PYR in the PE rat model.