Phosphorylation of extracellular signal-regulated kinases in bladder afferent pathways with cyclophosphamide-induced cystitis

Abstract

Extracellular signal-regulated kinases (ERK1 and ERK2) are phosphorylated in the nervous system after somatic or visceral stimulation or inflammation and play roles in central sensitization and pain hypersensitivity. ERK1/2 activation with cyclophosphamide (CYP)-induced cystitis has been demonstrated in urinary bladder and inhibitors of ERK1/2 phosphorylation reduce CYP-induced bladder hyperreflexia. In this study, we determined pERK1/2 expression and regulation in lumbosacral dorsal root ganglia (DRG) and spinal cord with CYP-induced cystitis (4 h, 48 h, chronic) using Western blotting and immunohistochemical techniques. Phosphorylated extracellular signal-regulated kinases (pERK1/2) expression was significantly (P≤0.01) upregulated in L6 and S1 DRG with CYP-induced cystitis with the greatest upregulation occurring at 4 h. No changes in pERK1/2 expression were observed in L1, L2 or L5 DRG or in any spinal cord segment examined (L1, L2, L5–S1) with CYP-induced cystitis. Cytoplasmic pERK1/2–immunoreactivity (IR) and pericellular pERK1/2–IR was observed in all DRG examined from control rats and cytoplasmic pERK1/2–IR was significantly (P≤0.01) increased in L6 and S1 DRG with 4 and 48 h CYP-induced cystitis. In contrast, pericellular pERK1/2–IR in DRG was not regulated by CYP-induced cystitis. A small percentage of bladder afferent cells in lumbosacral DRG expressed pERK1/2-IR in control rats; however, CYP-induced cystitis (48 h) significantly (P≤0.01) increased the percentage of bladder afferent cells in the L6 and S1 DRG exhibiting pERK1/2–IR. These studies suggest that activation of the ERK pathway in lumbosacral DRG may play a role in neuroplasticity in micturition reflexes with CYP-induced cystitis.