L- and T-type Ca2+ channels dichotomously contribute to retinal ganglion cell injury in experimental glaucoma

Hong-Ning Wang; Wen-Jing Qian; Guo-Li Zhao; Fang Li; Yan-Ying Miao; Bo Lei; Xing-Huai Sun; Zhong-Feng Wang

doi:10.4103/1673-5374.360277

L- and T-type Ca²⁺ channels dichotomously contribute to retinal ganglion cell injury in experimental glaucoma

Neural Regen Res. 2023 Jul;18(7):1570-1577. doi: 10.4103/1673-5374.360277.

Authors

Hong-Ning Wang¹, Wen-Jing Qian¹, Guo-Li Zhao¹, Fang Li¹, Yan-Ying Miao¹, Bo Lei², Xing-Huai Sun³, Zhong-Feng Wang¹

Affiliations

¹ State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China.
² Institutes of Neuroscience and Third Affiliated Hospital, Henan Provincial People's Hospital, Henan Eye Institute, Henan Eye Hospital, People's Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, Henan Province, China.
³ Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, NHC Key Laboratory of Myopia, Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China.

Abstract

Retinal ganglion cell apoptotic death is the main pathological characteristic of glaucoma, which is the leading cause of irreversible blindness. Disruption of Ca²⁺ homeostasis plays an important role in glaucoma. Voltage-gated Ca²⁺ channel blockers have been shown to improve vision in patients with glaucoma. However, whether and how voltage-gated Ca²⁺ channels are involved in retinal ganglion cell apoptotic death are largely unknown. In this study, we found that total Ca²⁺ current densities in retinal ganglion cells were reduced in a rat model of chronic ocular hypertension experimental glaucoma, as determined by whole-cell patch-clamp electrophysiological recordings. Further analysis showed that L-type Ca²⁺ currents were downregulated while T-type Ca²⁺ currents were upregulated at the later stage of glaucoma. Western blot assay and immunofluorescence experiments confirmed that expression of the Ca_V1.2 subunit of L-type Ca²⁺ channels was reduced and expression of the Ca_V3.3 subunit of T-type Ca²⁺ channels was increased in retinas of the chronic ocular hypertension model. Soluble tumor necrosis factor-α, an important inflammatory factor, inhibited the L-type Ca²⁺ current of isolated retinal ganglion cells from control rats and enhanced the T-type Ca²⁺ current. These changes were blocked by the tumor necrosis factor-α inhibitor XPro1595, indicating that both types of Ca²⁺ currents may be mediated by soluble tumor necrosis factor-α. The intracellular mitogen-activated protein kinase/extracellular signal-regulated kinase pathway and nuclear factor kappa-B signaling pathway mediate the effects of tumor necrosis factor-α. TUNEL assays revealed that mibefradil, a T-type calcium channel blocker, reduced the number of apoptotic retinal ganglion cells in the rat model of chronic ocular hypertension. These results suggest that T-type Ca²⁺ channels are involved in disrupted Ca²⁺ homeostasis and apoptosis of retinal ganglion cells in glaucoma, and application of T-type Ca²⁺ channel blockers, especially a specific Ca_V3.3 blocker, may be a potential strategy for the treatment of glaucoma.

Keywords: Ca_V1.2; Ca_V3.3; apoptosis; chronic ocular hypertension; extracellular signal-regulated kinase; mitogen-activated protein kinase; nuclear factor-kappa B; patch-clamp; retina; tumor necrosis factor-α.