Intra-Cellular Calcium Signaling Pathways (PKC, RAS/RAF/MAPK, PI3K) in Lamina Cribrosa Cells in Glaucoma

• Main Authors: Mustapha Irnaten, Aisling Duff, Abbot Clark, Colm O’Brien
• Format: Article
• Language: English
• Published: MDPI AG 2021-12-01
• Series: Journal of Clinical Medicine
• Subjects: glaucoma; lamina cribrosa; fibrosis; calcium; PKCα; <i>p</i>38-MAPK
• Online Access: https://www.mdpi.com/2077-0383/10/1/62

The lamina cribrosa (LC) is a key site of fibrotic damage in glaucomatous optic neuropathy and the precise mechanisms of LC change remain unclear. Elevated Ca²⁺ is a major driver of fibrosis, and therefore intracellular Ca²⁺ signaling pathways are relevant glaucoma-related mechanisms that need to be studied. Protein kinase C (PKC), mitogen-activated MAPK kinases (<i>p</i>38 and <i>p</i>42/44-MAPK), and the PI3K/mTOR axis are key Ca²⁺ signal transducers in fibrosis and we therefore investigated their expression and activity in normal and glaucoma cultured LC cells. We show, using Western immune-blotting, that hyposmotic-induced cellular swelling activates PKCα, <i>p</i>42/<i>p</i>44, and <i>p</i>38 MAPKs, the activity is transient and biphasic as it peaks between 2 min and 10 min. The expression and activity of PKCα, <i>p</i>38 and <i>p</i>42/<i>p</i>44-MAPKs are significantly (<i>p</i> < 0.05) increased in glaucoma LC cells at basal level, and at different time-points after hyposmotic stretch. We also found elevated mRNA expression of mRNA expression of PI3K, IP3R, mTOR, and CaMKII in glaucoma LC cells. This study has identified abnormalities in multiple calcium signaling pathways (PKCα, MAPK, PI3K) in glaucoma LC cells, which might have significant functional and therapeutic implications in optic nerve head (ONH) fibrosis and cupping in glaucoma.