Adjunctive Thymosin Beta-4 Treatment Influences MΦ Effector Cell Function to Improve Disease Outcome in Pseudomonas aeruginosa-Induced Keratitis.

Yuxin Wang,Abdul Shukkur Ebrahim,Elizabeth A Berger,Gabriel Sosne,Thomas W Carion

doi:10.3390/ijms222011016

Yuxin Wang, Abdul Shukkur Ebrahim + Show 3 more

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https://doi.org/10.3390/ijms222011016

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Abstract

Our previous work has shown that topical thymosin beta 4 (Tβ4) as an adjunct to ciprofloxacin treatment reduces inflammatory mediators and inflammatory cell infiltrates (neutrophils/PMN and macrophages/MΦ) while enhancing bacterial killing and wound healing pathway activation in an experimental model of P. aeruginosa-induced keratitis. This study aimed to mechanistically examine how Tβ4 influences MΦ function in particular, leading to reduced inflammation and enhanced host defense following P. aeruginosa-induced infection of the cornea. Flow cytometry was conducted to profile the phenotype of infiltrating MΦ after infection, while generation of reactive nitrogen species and markers of efferocytosis were detected to assess functional activity. In vitro studies were performed utilizing RAW 264.7 cells to verify and extend the in vivo findings. Tβ4 treatment decreases MΦ infiltration and regulates the activation state in response to infected corneas. MΦ functional data demonstrated that the adjunctive Tβ4 treatment group significantly downregulated reactive nitrogen species (RNS) production and efferocytotic activity. In addition, the in vitro studies showed that both Tβ4 alone and adjunctive Tβ4 treatment influenced MΦ cellular function following LPS stimulation. Collectively, these data provide further evidence that adjunctive Tβ4 + ciprofloxacin treatment offers a more efficacious option for treating bacterial keratitis. Not only does the adjunctive therapy address both the infectious pathogen and corneal wound healing response, but it also influences MΦ infiltration, activation, and function, as revealed by the current study.

Highlights

Bacterial keratitis is a rapidly progressing, sight-threatening infection of the cornea that can lead to corneal opacification, perforation, and endophthalmitis
Current antibiotic treatment for bacterial keratitis mainly addresses the pathogen with fourth-generation ophthalmic fluoroquinolone as the preferred choice for treating P. aeruginosa-infected corneas [6,7]
Disease response was significantly improved in ciprofloxacintreated corneas when compared to both PBS controls and Tβ4-treated mice

Summary

Introduction

Bacterial keratitis is a rapidly progressing, sight-threatening infection of the cornea that can lead to corneal opacification, perforation, and endophthalmitis. Pseudomonas aeruginosa is one of the most common pathogens identified in bacterial keratitis with an increasing frequency, especially among contact lens wearers and immunocompromised individuals [1,2,3]. Keratitis-induced corneal opacification is among the leading causes of blindness worldwide and results in a substantial economic burden on families, hospitals, and societies [4,5]. Current antibiotic treatment for bacterial keratitis mainly addresses the pathogen with fourth-generation ophthalmic fluoroquinolone as the preferred choice for treating P. aeruginosa-infected corneas [6,7]. Controlling bacteria in keratitis is very important, clinical outcomes can still be inferior due to host-induced corneal opacification that remains unresolved. Corticosteroid treatment addresses the host response to some extent; its use is not substantiated and usually is not recommended [9,10]

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