Functional analysis of mesencephalic astrocyte‐derived neurotrophic factor in retinal ganglion cells under oxidative stress

Abstract

Glaucoma is optic neuropathy that is characterized by progressive neurodegeneration of the retinal ganglion cells (RGCs) and axons. This condition will lead to visual impairment and bring glaucoma to become the second cause of blindness globally. Neuroprotection in glaucoma is needed to prevent the progression of optic neuropathy. In this study, we examined the effects of the superior colliculus (SC), and mesencephalic astrocyte‐derived neurotrophic factor (MANF) secreted from the SC, on RGC survival after oxidative stress. SC slices and RGCs from rats (3‐day old) were co‐cultured using a 3D‐transwell system. In addition, primary RGCs from 4 to 5‐day‐old rats were cultured and treated with 100 μM hydrogen peroxide (H2O2), together with stimulation by MANF. Immunoblot and immunofluorescence analyses indicated down‐regulated expression levels of several survival markers of RGCs. Extension of neurites was decreased in RGCs treated with 100 μM H2O2. Following co‐culture with SC slices, or the addition of MANF, we found that both the down‐regulated expression of neural markers and extension of neurites caused by oxidative stress in RGCs were blocked. Furthermore, we found a decrease in the expression of neural markers and extension of neurites after co‐culture with MANF siRNA‐treated SC slices compared with slices treated with mock siRNA, but, RGCs co‐cultured with SC slices treated with MANF siRNA displayed no‐changed about to apoptosis. These results suggest that MANF secreted from the SC may play an important role in maintenance of function and survival of RGCs. It is also possible that MANF is an important factor in neuroprotection of RGCs. Significance of the Study Glaucoma is a progressive neurodegenerative disease of the retinal ganglion cell (RGC) and their axons. Neuroprotection is aimed at protecting those neurons that are damaged glaucomatous optic neuropathy. We have now examined the effects of superior colliculus, or msencephalic astrocyte‐derived neutrophic factor (MANF), secreted from superior colliculus, on RGC survival using co‐culture system. Our results suggested that MANF may important key factor in neuroprotection of RGC.

Mesencephalic Astrocyte-Derived Neurotrophic Factor (MANF) Regulates Neurite Outgrowth Through the Activation of Akt/mTOR and Erk/mTOR Signaling Pathways

“…The role of MANF in neurite extension has been investigated in primary neurons and neural precursors as well as in animals. A study by Ko et al reported that MANF was required for the neurite extension and maintenance in cultured retinal ganglion cells (RGCs) isolated from 3 to 5 days old rat retina (Ko et al, 2020). Another study by Tseng et al, 2017a reported that complete conventional MANF knockout mice exhibit impaired neurite outgrowth in vivo, and MANF-deficient neuronal stem cells isolated from the embryonic day 13.5 (E13.5) knockout mice have defect in neurite extension when cultured and differentiated in vitro (Tseng et al, 2017a).…”

Upregulation of mesencephalic astrocyte‐derived neurotrophic factor (MANF) expression offers protection against alcohol neurotoxicity

“…Increased MANF immunofluorescent signal was also detected in N2a cells 12 h following alcohol exposure, which was co‐localized with the MANF‐interacting protein PDIA1 in the ER (Figure 1e; Eesmaa et al, 2021). Although MANF localized in the ER, its secretion can be induced in pathological conditions (Kim et al, 2016). Next, we detected the amount of secreted MANF in the conditioned media and found that it was elevated by alcohol treatment in a time‐dependent manner for both N2a and SH‐SY5Y cells (Figure 1c,d).…”

“…We also detected increased MANF secretion after alcohol exposure. Although MANF is located in the ER, its extracellular secretion has been reported to be protective against many ER stress‐associated diseases, including kidney diseases, skeletal diseases, diabetes, cardiac ischemia, stroke, and Parkinson's disease in rodent models and human patients (Airavaara et al, 2009; Galli et al, 2016, 2019; Hartley et al, 2013; Kim et al, 2016; Tadimalla et al, 2008; Voutilainen et al, 2009). The mechanism of MANF secretion is not fully understood.…”

“…MANF is involved in multiple neurodevelopment processes, including neurogenesis (Wang et al, 2022), neurite outgrowth (Tseng, Danilova, et al, 2017;Wen et al, 2020), and neuron migration (Tseng, Anttila, et al, 2017). Increasing evidence suggest that MANF not only regulates normal neurodevelopment and survival (Chen et al, 2012;Palgi et al, 2009) but also protects neurons from pathological conditions such as brain ischemia, Alzheimer's disease, Parkinson's disease, traumatic brain injury, and retinal degeneration (Airavaara et al, 2010;Apostolou et al, 2008;Chen et al, 2012;Gao et al, 2017;Ko et al, 2020;Lu et al, 2018;Neves et al, 2016;Palgi et al, 2009;Petrova et al, 2003;Voutilainen et al, 2009).…”