Long term effects of morphine on mesangial cell proliferation and matrix synthesis

Long term effects of morphine on mesangial cell proliferation and matrix synthesis. Since focal glomerulosclerosis is the predominant glomerular lesion in heroin nephropathy and since mesangial expansion is considered to be a precursor of glomerulosclerosis, we have evaluated the effect of opiates on mesangial cell (MC) proliferation and matrix synthesis. We showed, using a fluorometric assay, that MC are not capable of metabolizing heroin to its active metabolite morphine. Cells exposed to morphine (10 -5 M or 10 -4 M) in prolonged cultures either continuously (Group A) or intermittently (Group B) showed enhanced incorporation of [ 3 H]thymidine when compared to control cells (control, 88600 ± 26303 cpm/well vs. morphine 10 -4 M -Group A, 321203 ± 52867, P -4 M-Group B, 223126 ± 46866 cpm/well, P -5 M - Group A, 267108 ± 41866 cpm/well, P -5 M - Group B, 202317 ± 24325 cpm/well, P -6 M) enhanced DNA synthesis when exposed intermittently only (control, 107593 ± 42284 cpm/well vs. Group B, 219164 ± 15552 cpm/well, P -6 M and 10 -5 M) was also observed at earlier time points, that is, one- and one-and-a-half-week old cultures. However, in one-week-old cultures, morphine in a higher concentration (10 -4 M) showed a suppressive effect (P -4 M) treated cells enhanced MC proliferation. An opioid antagonist, naloxone attenuated the effect of morphine in one and half week old cultures. Morphine at 10 -6 M to 10 -4 M concentrations enhanced incorporation of [ 3 H]proline in the extracellular proline pool (a component of mesangial matrix) when compared to control (control, 309661 ± 3992 vs. morphine 10 -4 M, 363104 ± 10539 cpm/well, P -5 M, 397954 ± 31008 cpm/well, P -6 M, 384630 ± 26369 cpm/well, P -6 M and 10 -4 M) also enhanced (P -5 M or 10 -4 , 12 weeks) had a greater number of hillocks (foci of cell proliferation and aggregated matrix) when compared with untreated cells. Morphine treated MC synthesized a decreased amount of PGE 2 (129 ± 48 pg/mg protein, P 2 production by untreated cells (493 ±123 pg/mg protein). Morphine pretreated MC when stimulated with arginine vasopressin (AVP, 10 -6 M) also produced a lesser amount of PGE 2 (214 ± 51 pg/mg protein, P 2 production by control cells under stimulation with AVP (1393 ± 451 pg/mg protein). Our results suggest that morphine may be playing a direct role in mesangial expansion in opiate addicts.