Abstract
Renin angiotensin system (RAS) is a key hormonal system which regulates the cardiovascular function and is implicated in several autoimmune diseases. With the discovery of the angiotensin-converting enzyme 2 (ACE2), a protective axis of RAS namely ACE2/Ang-(1–7)/Mas that counteracts the deleterious ACE/AngII/AT1R axis has been established. This axis is emerging as a novel target to attenuate ocular inflammation. However, the underlying molecular mechanisms remain unclear. We investigated the hypothesis that enhancing the activity of the protective axis of RAS by subretinal delivery of an AAV8 (Y733F)-ACE2 vector would protect against the ocular inflammation in experimental autoimmune uveitis (EAU) mice through regulating the local immune responses. Our studies demonstrated that increased ACE2 expression exerts protective effects on inflammation in EAU mouse by modulating ocular immune responses, including the differentiation of Th1/Th17 cells and the polarization of M1/M2 macrophages; whereas the systemic immune responses appeared not affected. These effects were mediated by activating the Ang-(1–7)/Mas and inhibiting the MAPK, NF-κB and STAT3 signaling pathways. This proof-of-concept study suggests that activation of ocular ACE2/Ang-(1–7)/Mas axis with AAV gene transfer modulates local immune responses and may be a promising, long-lasting therapeutic strategy for refractory and recurrent uveitis, as well as other inflammatory eye diseases.
Highlights
We previously showed that the hyper-activation of the nuclear factor (NF)-κB and mitogen activated protein kinase (MAPK) signaling pathways were involved in the pathological process of experimental autoimmune uveitis (EAU) and EIU25,27
angiotensin-converting enzyme 2 (ACE2) was detected in porcine ciliary bodies and retinas39, and Ang-(1–7) and Mas were observed in the eyes40–43
We demonstrated that subretinal delivery of the ACE2 gene resulted in a robust expression of ACE2 at both mRNA and protein levels in the retina
Summary
ACE2/Ang-(1–7)/Mas axis acts as a negative regulator of the RAS and has become a vital therapeutic target in many inflammatory and autoimmune diseases, including type 1 diabetes, autoimmune myocarditis, and arthritis. ACE2/Ang-(1–7)/Mas axis acts as a negative regulator of the RAS and has become a vital therapeutic target in many inflammatory and autoimmune diseases, including type 1 diabetes, autoimmune myocarditis, and arthritis21 It is protective in several ocular immune diseases. We demonstrated that activating the endogenous ACE2 both systemically and locally evoked beneficial effects by attenuating the inflammation of endotoxin induced uveitis (EIU) in mice and rats. We hypothesize that over-expression of ACE2 attenuates the ocular local inflammation in EAU mouse by activating the protective ACE2/Ang-(1–7)/Mas axis and by inhibition of MAPK, NF-κBand STAT3 pathways. We employed adeno-associated virus vector serotype 8 (AAV8) vector containing a tyrosine-capsid mutant (Y733F) to deliver the ACE2 gene subretinally since this capsid-modified vector has been shown to provide rapid and efficient gene transduction in adult mouse retina
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