Abstract
Purpose:
Bisphosphonates are the most commonly prescribed drugs used to treat osteoporosis. In addition to a recent report supporting an association between bisphosphonate use and ocular inflammation (Etminan et al., 2012), preliminary data also support an association between bisphosphonate use and age-related macular degeneration (AMD). Therefore, we studied the effects of bisphosphonates on primary culture of human retinal pigment epithelium (hRPE), a cell type known to secrete pro-inflammatory cytokines in the outer retina. Alendronate, an amino-bisphosphonate, and etidronate, a non-amino-bisphosphonate, were selected for this experiment as they are members of the two structurally different classes of bisphosphonates.
Methods:
Primary cultures of hRPE were serum-starved for 24 hours and then treated for 24 hours with alendronate (0.0001, 0.1, 100 µM) and etidronate (0.01, 1 µM). Cell viability was measured using the MTT assay. Investigation of cytokines induced by bisphosphonates was performed using a human cytokine 29-Plex Panel (Bio-Plex) array and the results were analyzed with an ANOVA.
Results:
Etidronate, at the lower concentration, significantly increased the expression of IL-6 (p=0.03) and IL-8 (p=0.04). At the higher concentration, etidronate significantly decreased the expression of GM-CSF (p=0.02) and bFGF (p=0.02). Alendronate, at the highest concentration, significantly increased the expression of IL-8 (p=0.02) and decreased the expression of eotaxin (p=0.02). Alendronate also significantly decreased the expression of bFGF at all concentrations (p<0.05). Alendronate and etidronate did not significantly alter the expression of the other cytokines measured. Cell viability was not significantly affected by either alendronate or etidronate treatment for 24h.
Conclusions:
Alendronate and etidronate display dose dependent effects in hRPE cells. Etidronate at lower concentration and alendronate at higher concentration appear to induce pro-inflammatory effects. In addition, anti-angiogenic effects of both drugs were demonstrated by the reduction in bFGF and eotaxin expression observed with the highest concentration of alendronate. The anti-angiogenic effects observed are consistent with a previous study (Nagai et al., 2007). Further studies are required to elucidate the association between bisphosphonate use and AMD.
Keywords: 412 age-related macular degeneration •
557 inflammation •
490 cytokines/chemokines