Evaluation of Annexin A1 Protein in an Infectious Keratitis Model: Therapeutic Perspectives

Abstract

Introduction: bacterial keratitis caused by Pseudomonas aeruginosa is one of the causes of blindness in the world, due to pathogenicity of the bacteria that can lead to corneal perforation. Studies on the protein annexin A1 (AnxA1) point it as one of the essential mediators in homeostasis of inflammation and ocular infections. However, there are no known reports of AnxA1 in keratitis. Objetive: to investigate the expression profile of AnxA1 in the P. aeruginosainduced keratitis model in two strains of mice (susceptible and pathogen resistant).Method: for the development of experimetal keratitis, the mice had their right eyes ulcerated and immediately inoculated with 5 μl of P. aeruginosa in PBS. The animals were euthanized after 24 hours of the bacteria inoculation. The eyes were clinically evaluated and histopathologically processed for quantitative analyses of the inflammatory infiltrate and immunohistochemical studies of the expressions of the AnxA1 and the receptor for formylated peptides (fpr2).Results: our results demonstrated a higher influx of inflammatory cells, mainly neutrophils in the susceptible animals (C57BL / 6) compared to those considered resistant (BALB / c) and controls. Immunohistochemical studies indicated weak expression of AnxA1 and fpr2 in the anterior epithelium and stroma of the cornea. However, after keratitis induction, overexpression of AnxA1 and fpr2 occurred in the corneas of both mice strains. Furthermore, greater expression of AnxA1 in the anterior corneal epithelium was observed in the C57BL / 6 animals.Conclusions: AnxA1 and fpr2 may be related to infectious keratitis induced by P.aeruginosa, which stimulates further investigations on the use of AnxA1 as a possible coadjuvant therapeutic strategy in bacterial keratitis.

Annexin A1 Mimetic Peptide and Piperlongumine: Anti-Inflammatory Profiles in Endotoxin-Induced Uveitis

“…The immunohistochemical analysis of untreated EIU eyes showed an increase in the intensity of immunolabeling for AnxA1, corroborating our previous findings in ocular tissues [17,34] and ocular inflammatory cells [16]. The higher expression of AnxA1 was also observed in neutrophils in ocular toxoplasmosis in mice and culture of retinal pigmented cells infected with Toxoplasma gondii [30].…”

“…Although our results indicated that the combination of the peptide with PL promoted a decrease in the effects of Ac2-26, the dosage of 200 µg of PL still allowed the peptide actions in a moderate manner, which may explain the lower expression of the endogenous AnxA1 in this group. Modulation in the expression of AnxA1 after LPS inoculation found in this investigation reinforces the involvement of the protein in ocular tissue physiology during inflammatory [16,17], infectious [34], allergic [32,35], and autoimmune [18,20] processes in experimental models. Interestingly, the expression of AnxA1 remains increased after treatments with PL singly administered or at 400 µg dosage in combination with the peptide.…”

“…Several investigations have explored the anti-inflammatory and protective activities of AnxA1 protein and its mimetic peptides, especially Ac2-26 [25,29]. In recent years, our group has researched the role of AnxA1 in the eye by means of in vivo and in vitro studies and highlighted the potential of the protein in controlling the ocular inflammatory process [16,17,19,34,35]. Recently, the understanding that AnxA1 could interact with PL [36] has opened up a new and exciting field of research.…”

“…Over the years, our research group has investigated the effect of AnxA1 on different ocular inflammatory conditions [17,19,[30][31][32][33][34][35]. Positive modulation of endogenous AnxA1 in inflammatory cells in the eyes of mice and retinal pigment epithelial cells (ARPE- 19) infected with Toxoplasma gondii suggests the protein can be used as a therapeutic target in ocular toxoplasmosis [30].…”

“…In addition, the potential involvement of the formyl peptide receptor (fpr) family in the protective effect of Ac2-26 was investigated in the same allergic conjunctivitis model [35]. In a Pseudomonas aeruginosa keratitis model, the overexpression of AnxA1 and fpr2 occurred in the corneas of Balb/c mice and especially C57BL/6 mice, which is more susceptible to pathogens and infectious antigens [34]. Concerning the uveitis, the expression of AnxA1 in leukocytes and aqueous humor (AqH) was observed in endotoxin-induced uveitis (EIU) in rats [16], with this protein noted as one of the essential mediators in the inflammatory homeostasis process.…”