Chitosan-Rapamycin Carbon Dots Alleviate Glaucomatous Retinal Injury by Inducing Autophagy to Promote M2 Microglial Polarization

Abstract

Qi Wang,1– 3,* Jiaxin Dong,4,* Mengxian Du,1,3,* Xinna Liu,1– 3 Shiqi Zhang,1 Di Zhang,1,3 Wanyun Qin,1,3 Xikun Xu,1,2 Xianghui Li,1,3 Ruidong Su,1,2 Leyi Qiu,1,2 Baoqiang Li,4,5 Huiping Yuan1 1Department of Ophthalmology, The Second Affiliated Hospital of Harbin Medical University, Harbin, People’s Republic of China; 2The Key Laboratory of Myocardial Ischemia, Harbin Medical University, Ministry Education, Harbin, People’s Republic of China; 3Future Medical Laboratory, the Second Affiliated Hospital of Harbin Medical University, Harbin, People’s Republic of China; 4Institute for Advanced Ceramics, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, People’s Republic of China; 5Laboratory of Dynamics and Extreme Characteristics of Promising Nanostructured Materials, Saint Petersburg State University, St. Petersburg, Russia*These authors contributed equally to this workCorrespondence: Huiping Yuan, Department of Ophthalmology, The Second Affiliated Hospital of Harbin Medical University, Harbin, 150081, People’s Republic of China, Email [email protected] Baoqiang Li, Institute for Advanced Ceramics, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150081, People’s Republic of China, Email [email protected]: Glaucoma is a prevalent cause of irreversible vision impairment, characterized by progressive retinal ganglion cells (RGCs) loss, with no currently available effective treatment. Rapamycin (RAPA), an autophagy inducer, has been reported to treat glaucoma in rodent models by promoting RGC survival, but its limited water solubility, systemic toxicity, and pre-treatment requirements hinder its potential clinical applications.Methods: Chitosan (CS)-RAPA carbon dot (CRCD) was synthesized via hydrothermal carbonization of CS and RAPA and characterized by transmission electron microscopy, Fourier transform infrared spectra, and proton nuclear magnetic resonance. In vitro assays on human umbilical cord vein endothelial and rat retinal cell line examined its biocompatibility and anti-oxidative capabilities, while lipopolysaccharide-stimulated murine microglia (BV2) assays measured its effects on microglial polarization. In vivo, using a mouse retinal ischemia/reperfusion (I/R) model by acute intraocular pressure elevation, the effects of CRCD on visual function, RGC apoptosis, oxidative stress, and M2 microglial polarization were examined.Results: CRCD exhibited good water solubility and anti-oxidative capabilities, in the form of free radical scavenging. In vitro, CRCD was bio-compatible and lowered oxidative stress, which was also found in vivo in the retinal I/R model. Additionally, both in vitro with lipopolysaccharide-stimulated BV2 cells and in vivo with the I/R model, CRCD was able to promote M2 microglial polarization by activating autophagy, which, in turn, down-regulated pro-inflammatory cytokines, such as IL-1β and TNF-α, as well as up-regulated anti-inflammatory cytokines, such as IL-4 and TGF-β. All these anti-oxidative and anti-inflammatory effects ultimately aided in preserving RGCs, and subsequently, improved visual function.Discussion: CRCD could serve as a potential novel treatment strategy for glaucoma, via incorporating RAPA into CDs, in turn not only mitigating its toxic side effects but also enhancing its therapeutic efficacy. Keywords: retina, ischemia/reperfusion injury, rapamycin, carbon dots, microglial polarization, autophagy

Keywords

• retina
• ischemia/reperfusion injury
• rapamycin
• carbon dots
• microglial polarization
• autophagy