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Long term effects of morphine on mesangial cell proliferation and matrix synthesis
P C Singhal1, N Gibbons, M Abramovici
1Department of Medicine, Long Island Jewish Medical Center, New Hyde Park, New York.
Abstract:
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 [3H]thymidine when compared to control cells (control, 88600 +/- 26303 cpm/well vs. morphine 10(-4) M-Group A, 321203 +/- 52867, P less than 0.001; control vs. morphine 10(-4) M-Group B, 223126 +/- 46866 cpm/well, P less than 0.01; control, 107593 +/- 42284 cpm/well vs. morphine 10(-5) M - Group A, 267108 +/- 41866 cpm/well, P less than 0.001; control vs. morphine 10(-5) M - Group B, 202317 +/- 24325 cpm/well, P less than 0.05). However, MC incubated with a lower concentration of morphine (10(-6) M) enhanced DNA synthesis when exposed intermittently only (control, 107593 +/- 42284 cpm/well vs. Group B, 219164 +/- 15552 cpm/well, P less than 0.05). This growth stimulating effect of morphine (10(-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 less than 0.05) on MC proliferation (morphine, 3620 +/- 220 cpm/well vs. control, 4668 +/- 410 cpm/well). This effect not only subsided by one and a half weeks but morphine (10(-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 [3H]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 less than 0.05 or morphine 10(-5) M, 397954 +/- 31008 cpm/well, P less than 0.001 or morphine 10(-6) M, 384630 +/- 26369 cpm/well, P less than 0.01). In addition, MC incubated with morphine (10(-6) M and 10(-4) M) also enhanced (P less than 0.001) synthesis of laminin.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Morphine stimulates mesangial cell proliferation and matrix synthesis, contributing to focal glomerulosclerosis in heroin nephropathy. Naloxone, an opioid antagonist, reversed these effects, highlighting the role of opioid receptors in kidney damage.
Area of Science:
- Nephrology
- Pharmacology
- Cell Biology
Background:
- Focal glomerulosclerosis is a key lesion in heroin nephropathy.
- Mesangial expansion precedes glomerulosclerosis development.
- Understanding opiate effects on mesangial cells is crucial for heroin nephropathy research.
Purpose of the Study:
- To investigate the impact of opiates, specifically morphine, on mesangial cell (MC) proliferation and matrix synthesis.
- To determine if MCs metabolize heroin into active compounds like morphine.
Main Methods:
- Utilized fluorometric assays to measure [3H]thymidine incorporation (DNA synthesis) and [3H]proline incorporation (matrix synthesis) in cultured MCs.
- Exposed MCs to varying concentrations of morphine (10(-6) M to 10(-4) M) under continuous and intermittent culture conditions.
- Administered naloxone, an opioid antagonist, to assess its effect on morphine-induced changes.
Main Results:
- Morphine exposure significantly enhanced MC proliferation and [3H]thymidine incorporation, particularly at concentrations of 10(-5) M and 10(-4) M.
- Morphine also increased [3H]proline incorporation into the extracellular proline pool, indicating enhanced matrix synthesis.
- The opioid antagonist naloxone attenuated the effects of morphine on MCs.
- A biphasic effect of morphine on proliferation was observed, with initial suppression at 10(-4) M in one-week cultures, followed by enhancement.
Conclusions:
- Morphine directly stimulates mesangial cell proliferation and extracellular matrix synthesis.
- These findings suggest that morphine plays a direct role in the pathogenesis of heroin nephropathy.
- Opioid receptor antagonism may offer a therapeutic strategy for mitigating opiate-induced kidney damage.