Respuesta neurodegenerativa y neuroinflamatoria en la retina de ratones por inflamación sistémica, daño axonal o envejecimiento

Abstract

This thesis investigates the response of the retinas of male and female mice to injuries or diseases of various etiologies, using the following models: a) LPS-induced sepsis model to explore the effect of systemic inflammation on the retina; b) optic nerve crush (ONC) model to study the degeneration of retinal ganglion cells (RGCs) following traumatic damage and the neuroprotective potential of estrogen receptor alpha and beta (ER-α and ER-β) agonism; c) STZ-induced type 1 diabetes (T1D) model to study retinal damage caused by acute hyperglycemia; d) db/db mouse model of type 2 diabetes (T2D) to investigate vascular and neurodegenerative changes related to diabetes and obesity; e) mice across their lifespan to study retinal dysfunction and age-related neuronal degeneration. Objectives: In both sexes: 1) to evaluate the effect of LPS-induced systemic inflammation on the retinas of male and female mice, determine whether P2X7R and TNFR1 antagonism is neuroprotective, and explore the involvement of the inflammasome; 2) to analyze the progression of RGC death following ONC, the expression of ERs in the retina, and whether ER agonism is neuroprotective; 3) to investigate whether T1D and T2D induce RGC loss, gliosis, and changes in retinal vascularization; and 4) to examine the impact of aging on retinal structure and function. Methods: Male and female C57/BL6 mice were used, in which sepsis was induced (LPS), the optic nerve was axotomized, or type 1 diabetes (T1D) was induced (STZ). We also used db/db mice (T2D) and mice deficient in inflammasome components. Pharmacological treatments were administered intravitreally or systemically. The retina was assessed in vivo using spectral-domain optical coherence tomography (SD-OCT) and electroretinography (ERG). Cytokine levels were measured using ELISA, lymphoid infiltration by flow cytometry, and microglial activation, RGC death, neuroprotection, estrogen receptor expression, and vascular status were analyzed by immunohistochemistry. Results: 1. Sepsis induced significant loss of Brn3a+ RGCs and retinal dysfunction, which was greater in males than in females. TNF and IL-1β levels increased in the retinas of both sexes, while LT-α levels increased only in males. Antagonism of P2X7R and TNFR1 provided neuroprotection, and P2X7R antagonism also restored retinal function, especially in females. GSDMD deficiency protected RGCs. 2. Most RGCs expressed ER-α and ER-β. Optic nerve crush (ONC)-induced RGC loss occurred earlier in males. ER-β agonism delayed ONC-induced RGC loss in both sexes. 3. In diabetic mice, no RGC loss, microglial activation, or vascular changes were observed in either sex at the ages studied. 4. Aging caused functional deterioration, retinal thinning, and an increase in retinal area, although without neuronal loss. Male mice showed earlier loss of pSTR wave function, while female mice exhibited earlier impairment of b-wave function. Conclusions: Except in the diabetes models, where no morphological alterations were found in the retina, there is sexual dimorphism in the retinal response to sepsis, optic nerve axotomy, and aging. Therefore, it is crucial to study both male and female preclinical animal models to ensure that the results can be effectively translated to clinical settings and to develop therapies tailored to each sex.