Abstract
Sickle cell nephropathy is poorly understood and currently lacks any specific therapeutic options. Opioids are used to treat the pain associated with sickle cell disease. Interestingly, heroin (a metabolic precursor of morphine) is associated with glomerulosclerosis. Glomerulomegaly, an early sign of kidney damage, predicts the eventual severity of glomerulosclerosis. Using transgenic sickle mice as a disease model, we evaluated the effects of chronic opioid exposure on kidney pathology in the setting of sickle cell disease.Transgenic sickle cell mice (carry a single copy of linked transgenes for human alpha and beta-S globins and are homozygous for deletion of murine beta major globin) were treated for three weeks with PBS, morphine (50–150mg/70kg human equivalent), naloxone (equimolar to morphine), or morphine and naloxone (n=6 per group). We evaluated the effects of morphine on kidney pathology by assessing kidney weight, glomerular volume (by the Weibel-Gomez method), and mesangial cell counts per glomerulus. Morphine stimulated kidney growth in transgenic sickle mice. Treatment with morphine significantly increased glomerular volume and mesangial cell counts per glomerulus compared to PBS. These effects were reversed with the addition of naloxone to morphine. (see Table)Morphine-stimulated cultured mouse mesangial cells underwent proliferation, which was inhibited with the addition of naloxone (202% ±14.3 vs. 108% ±12.9 increase over control, p<0.01). Morphine-stimulated mesangial cells had increased expression of phosphorylated STAT-3 by western blot analysis. Blockade of STAT-3 with PpYLKTK-mts (0.2mM) resulted in inhibition of morphine-stimulated mesangial cell proliferation (202% ±14.3 vs.110±29, p<0.01).In summary, morphine exposure markedly induced kidney growth in transgenic sickle mice, as evidenced by increased kidney size, glomerular volume, and glomerular cell counts. Furthermore, morphine stimulates a proliferative response in mesangial cells via STAT-3 signaling. These results suggest morphine may accelerate renal injury in sickle cell disease.GroupKidney Weight (g)Glomerular Volume (mm3)#MC/glomerulusSickle PBS0.190 ± 0.02133 ± 727 ± 0.5Sickle Naloxone0.176 ± 0.01124 ± 1326 ± 1.2Sickle Morphine0.251 ± 0.04 λ163 ± 14 λ37 ± 1.9 λSickle MS+ Nal0.193 ± 0.01 π127 ± 12 π30 ± 1.5 γResults (mean ± SD): λ p<0.01 vs. Sickle PBS; π p=0.01 vs. Sickle MS; γ p<0.01 vs. Sickle MS.
Published Version
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