Background: Pain and renal dysfunction occur in sickle cell disease. Morphine used to treat pain also co-activates platelet-derived growth factor receptor-β (PDGFR-β), which can adversely affect renal disease. We examined the influence of morphine in mesangial cells in vitro and in mouse kidneys in vivo.
Methods: > Mouse mesangial cells treated with 1 μM morphine in vitro or kidneys of transgenic homozygous or hemizygous sickle or control mice (n=3 for each), treated with morphine (0.75, 1.4, 2.14, 2.8, 3.6, and 4.3 mg kg(-1) day(-1) in two divided doses during the first, second, third, fourth, fifth, and sixth weeks, respectively), were used. Western blotting, bromylated deoxy uridine incorporation-based cell proliferation assay, reverse transcriptase-polymerase chain reaction, immunofluorescent microscopy, and blood/urine chemistry were used to analyse signalling, cell proliferation, opioid receptor (OP) expression, and renal function.
Results: Morphine stimulated phosphorylation of PDGFR-β and mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) to the same extent as induced by platelet-derived growth factor-BB (PDGF-BB) and promoted a two-fold increase in mesangial cell proliferation. The PDGFR-β inhibitor, AG1296, OP antagonists, and silencing of μ- and κ-OP abrogated morphine-induced MAPK/ERK phosphorylation and proliferation by ~100%. Morphine treatment of transgenic mice resulted in phosphorylation of PDGFR-β, MAPK/ERK, and signal transducer and activator of transcription 3 (Stat3) in the kidneys. Morphine inhibited micturition and blood urea nitrogen (BUN) clearance and increased BUN and urinary protein in sickle mice.
Conclusion: Morphine stimulates mitogenic signalling leading to mesangial cell proliferation and promotes renal dysfunction in sickle mice.
Keywords: morphine; nephropathy; pain; platelet-derived growth factor; sickle cell disease.