Antimicrobial Effects of Thymosin Beta-4 and Ciprofloxacin Adjunctive Therapy in Pseudomonas aeruginosa Induced Keratitis.

Thomas W Carion,Abdul Shukkur Ebrahim,Thanzeela Ebrahim,Tressa Parker,Elizabeth A Berger,Julia Burns,Gabriel Sosne,Spandana Alluri

doi:10.3390/ijms21186840

Thomas W Carion, Abdul Shukkur Ebrahim + Show 6 more

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https://doi.org/10.3390/ijms21186840

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Abstract

Prior work has indicated that thymosin beta 4 (Tβ4) administered with ciprofloxacin markedly improves disease outcome for Pseudomonas aeruginosa (PA)-induced keratitis. As a result, the goal of the current study was to elucidate mechanisms by which Tβ4 mitigates the corneal response; specifically, regarding its bactericidal influence and potential synergy with ciprofloxacin. An in vitro approach was carried out using minimum inhibitory concentration (MIC) assays to assess bactericidal activity against PA. In addition, antimicrobial peptide (AMP) production was evaluated at the mRNA levels using human corneal epithelial cells in response to lipopolysaccharide (LPS) challenge. The results of the MIC assays did not show direct bactericidal activity with Tβ4 alone, although ciprofloxacin exhibited significant killing at concentrations far lower than clinically dosed. Tβ4, however, displayed an indirect effect on bacterial killing, as shown by an upregulation of AMPs and related molecules. The cumulative data from this study indicate an indirect bactericidal role of Tβ4, as well as a synergistic relationship with ciprofloxacin. Furthermore, ciprofloxacin alone was found to influence cellular functions that otherwise have yet to be reported. These results highlight a mechanism of intracellular communication for Tβ4 and further strengthen its development as an adjunct therapy with antibiotics for corneal infections.

Highlights

Bacterial keratitis is a deleterious infection of the cornea that causes corneal scarring, opacification, and perforation
All concentrations of Tβ4 remained similar to untreated controls for both concentrations of bacteria, indicating a lack of bactericidal effect
Bacterial keratitis is an extremely debilitating and rapidly progressive infection of the cornea which can advance into sight-threatening consequences including endophthalmitis and corneal opacification

Summary

Introduction

Bacterial keratitis is a deleterious infection of the cornea that causes corneal scarring, opacification, and perforation While this disease is commonly associated with contact lens wear, risk factors include refractive corneal surgery and immunocompromised conditions [1,2]. The use of relevant corticosteroids effectively dampen the host inflammatory response, steroid-induced glaucoma, impaired wound healing, and increased risk of infection are among the considerable drawbacks [5]. To this end, this study is focused on the development of an alternative therapy for the treatment of infectious corneal diseases. It is a type II cytokeratin, one of a number of isoforms of keratin 6 encoded by separate genes from the gene cluster on human chromosome 12q

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