PGE2 Causes Mesangial Cell Hypertrophy and Decreases Expression of Cyclin D3

Abstract

Background/Aims: Glomerular hypertrophy is a feature of many glomerular diseases and is associated with the development of renal failure. We previously demonstrated that the cyclooxygenase 2 inhibitor, NS398, reduced glomerular size after uninephrectomy. Thus, we hypothesized that prostaglandin (PG) E₂ would cause mesangial cell hypertrophy in vitro. Methods: We used a mesangial cell line and primary culture of rat mesangial cells. The effects of PGE₂ on mesangial cell hypertrophy were determined using immunohistochemistry and image analysis to assess cell size, 3H-leucine incorporation as a measure of protein synthesis and flow cytometry to assess cell cycle status. Western blot was used to examine the effect of PGE₂ on expression of cyclin D3, p15, p27 and cyclin-dependent kinase 4 – known regulators of the cell cycle. Results: PGE₂ increased cell size by 13% and protein synthesis (3H-leucine incorporation) by 35% over 24 h. By flow cytometry, PGE₂ increased the percentage of cells in G0/G1 phase of the cell cycle from 70.13 ± 1.01 to 74.06 ± 1.18% and conversely, decreased the number of cells in S phase from 24.07 ± 1.06 to 22.03 ± 0.78%. The number of cells in G2/M was also reduced. Expression of cyclin D3 was decreased by 60% after treatment with PGE₂, while expression of p27 was increased. The effects of PGE₂ on cell size and flow cytometry were reproduced by the prostaglandin E₂ receptors EP1/EP3 agonist sulprostone. Conclusion: PGE₂ induces mesangial cell hypertrophy and cell cycle arrest via its EP1 receptor.