Interaction of LPA1 and P2X3 Receptors in DRG Neurons: Implications for Cyclophosphamide-Induced Bladder Pain Syndrome in Mice

Abstract

Background: Despite the coexpression of Lysophosphatidic Acid-1 (LPA1) and purinergic receptor P2X, ligand-gated ion channel 3 (P2X3) receptors in vesicle-associated primary sensory neurons, their potential interaction contributing to bladder pain pathophysiology remains obscure. In this study, we aimed to investigate whether the interaction between LPA1 and P2X3 receptors in dorsal root ganglion (DRG) neurons drives the development of cyclophosphamide (CYP) -induced bladder pain syndrome. Methods: We induced bladder pain syndrome in male C57BL/6J mice via intraperitoneal administration of CYP (300 mg/kg). The experimental mice are grouped into saline (i.t.), CYP (i.p.), LPA (i.t.), Ki16198 (i.t.), A317491 (i.t.). A combination of behavioral, neuropharmacological, molecular biological, neuroretrograde tracing, and electrophysiological techniques was employed to investigate the mechanisms of LPA1 and the P2X3 receptor in bladder pain syndrome. Results: Administration of CYP resulted in bladder pain-like nociceptive behavior and a significant surge in urinary bladder LPA content and triggers the release of inflammatory factors Nuclear Factor Kappa-Light-Chain-Enhancer of Activated B Cells (NF-κB) and Interleukin-1 beta (IL-1β), resulting in pain-like nociceptive behavior. Nociceptive behavior was emulated through intrathecal injection of LPA (2.5 μg, 5 μL), which was significantly mitigated by the LPA1 receptor antagonist, Ki16198. α,β-meATP (100 μM) induced a significant increase in inward currents and action potential frequency in mouse DRG neurons, which was effectively counteracted by Ki16198. Direct application of LPA under physiological conditions also amplified the function of P2X3 receptors. While Ki16198 did not influence the upregulation of phosphorylated Extracellular Signal-Regulated Kinase (p-ERK) protein, it notably inhibited p38 protein. The selective p-38 antagonist SB202190 inhibited the upregulation of P2X3 recepor (P2X3R) as well as the levels of NF-κB and IL-1β, both of which were suppressed by the application of Ki16198 (i.t.). Conclusions: In summary, our study suggests that targeting the p38 mitogen-activated protein kinase (MAPK) signaling pathway may offer therapeutic potential for alleviating bladder pain in mice by mitigating the sensitization of LPA-LPA1 receptor signaling to the nociceptive receptor P2X3R in DRG neurons.