Mechanism of Ziyin Mingmu Fomula in treating retinitis pigmentosa by inhibiting photoreceptor apoptosis through Akt/FoxO1/FasL pathway
Objective To observe the effects of Ziyin Mingmu Fomula(ZYMMF)on the expressions of phosphorylated protein kinase B(p-Akt),forkhead box transcription factor O1(FoxO1),and Fas ligand(FasL)in the retinal tissue of mice with retinitis pigmentosa(RP),so as to explore the mechanism of ZYMMF in inhibiting photoreceptor apoptosis.Methods A total of 60 rd10 mice were randomized into model group,low-,medium-,and high-dose ZYMMF groups[10 g/(kg·d),20 g/(kg·d),and 40 g/(kg·d),respectively],and vitamin A group[5 g/(kg·d)],with 12 mice in each group.Additionally,twelve C57 mice were used as blank control group(equal amount of normal saline).Each group was continuously intervened for 28 d.Fundus photography was used to observe the morphological changes of the fundus of mice,and electroretinography was performed to record a-and b-wave amplitudes.HE staining was used to observe the pathological changes in the retinal tissue of mice and determine the thickness of the outer nuclear layer,and Western blot was used to check the protein expressions of p-Akt,FoxO1,FasL,cysteine aspartate-specific protease(Caspase)-3,and Caspase-8 in the retinal tissue.Results Compared with blank control group,the retina in model group showed pale and deformed optic disc,vascular atrophy,reduced amplitudes of both a-and b-waves in the electroretinogram(P＜0.01),blurred retinal structure,unclear boundaries of each layer,massive loss of photoreceptor cells,significant thinning of the outer nuclear layer(P＜0.01),significantly lower p-Akt protein expression level(P＜0.01),and markedly higher protein expression levels of FoxO1,FasL,Caspase-3,and Caspase-8(P＜0.01).Compared with model group,the fundus blood vessels in medium-and high-dose ZYMMF groups and vitamin A group were clearer,the optic disc showed no paleness,each layer of the retina was structured clearly,and the cells were arranged relatively neatly.Compared with model and low-dose ZYMMF groups,medium-and high-dose ZYMMF groups showed significantly increased a-and b-wave amplitudes and thicker outer nuclear layer of retina(P＜0.01),and vitamin A group showed significantly increased b-wave amplitude and also obviously thicker outer nuclear layer of retina(P＜0.01).Compared with medium-dose ZYMMF group,high-dose ZYMMF group showed significantly elevated a-and b-wave amplitudes and thicker outer nuclear layer of retina(P＜0.01),while vitamin A group showed significantly decreased a-and b-wave amplitudes(P＜0.01).Compared with high-dose ZYMMF group,vitamin A group showed obviously decreased a-and b-wave amplitudes and thinner outer nuclear layer of retina(P＜0.01).Compared with model group,the protein expression level of p-Akt in low-,medium-,and high-dose ZYMMF groups and vitamin A group was significantly higher(P＜0.01),while those of FoxO1,FasL,and Caspase-3 were lower(P＜0.05,P＜0.01);the Caspase-8 protein expression level in medium-and high-dose ZYMMF groups was significantly reduced(P＜0.01).Compared with low-dose ZYMMF group,the p-Akt protein expression level in high-dose ZYMMF and vitamin A groups was obviously elevated(P＜0.01),and the protein expression levels of FoxO1,FasL,Caspase-3,and Caspase-8 in medium-and high-dose ZYMMF groups were significantly reduced(P＜0.01).Compared with medium-dose ZYMMF group,the p-Akt protein expression level in high-dose ZYMMF and vitamin A groups was significantly higher(P＜0.01),the protein expression levels of FoxO1,Caspase-3,and Caspase-8 in high-dose ZYMMF group were significantly lower(P＜0.01),and those of FoxO1,FasL,Caspase-3,and Caspase-8 in vitamin A group were significantly higher(P＜0.01).Compared with high-dose ZYMMF group,vitamin A group showed obviously lower p-Akt protein expression level(P＜0.01)but significantly higher protein expression levels of FoxO1,FasL,Caspase-3,and Caspase-8(P＜0.01).Conclusion ZYMMF may enhance p-Akt expression and inhibit protein expressions of FoxO1 and its downstream genes such as FasL,Caspase-3,and Caspase-8 by regulating Akt/FoxO1/FasL pathway,thereby reducing the retinal apoptosis in rd10 mice,protecting the retinal structure and function,and delaying the progression of RP.
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