Abstract
BackgroundChlamydia trachomatis is an intracellular bacterium that resides in the conjunctival and reproductive tract mucosae and is responsible for an array of acute and chronic diseases. A percentage of these infections persist even after use of antibiotics, suggesting the need for alternative treatments. Previous studies have demonstrated anti-bacterial effects using different wavelengths of visible light at varying energy densities, though only against extracellular bacteria. We investigated the effects of visible light (405 and 670 nm) irradiation via light emitting diode (LEDs) on chlamydial growth in endocervical epithelial cells, HeLa, during active and penicillin-induced persistent infections. Furthermore, we analyzed the effect of this photo treatment on the ensuing secretion of IL-6 and CCL2, two pro-inflammatory cytokines that have previously been identified as immunopathologic components associated with trichiasis in vivo.ResultsC. trachomatis-infected HeLa cells were treated with 405 or 670 nm irradiation at varying energy densities (0 – 20 J/cm2). Bacterial growth was assessed by quantitative real-time PCR analyzing the 16S: GAPDH ratio, while cell-free supernatants were examined for IL-6 and monocyte chemoattractant protein-1 (CCL2) production. Our results demonstrated a significant dose-dependent inhibitory effect on chlamydial growth during both active and persistent infections following 405 nm irradiation. Diminished bacterial load corresponded to lower IL-6 concentrations, but was not related to CCL2 levels. In vitro modeling of a persistent C. trachomatis infection induced by penicillin demonstrated significantly elevated IL-6 levels compared to C. trachomatis infection alone, though 405 nm irradiation had a minimal effect on this production.ConclusionTogether these results identify novel inhibitory effects of 405 nm violet light on the bacterial growth of intracellular bacterium C. trachomatis in vitro, which also coincides with diminished levels of the pro-inflammatory cytokine IL-6.
Highlights
Chlamydia trachomatis is an intracellular bacterium that resides in the conjunctival and reproductive tract mucosae and is responsible for an array of acute and chronic diseases
Fluorescent staining (FITC) for chlamydial antigens supported an impairment of chlamydial growth and inclusion body expansion after 405 nm exposure (Figure 2D-F, 20 J/cm2) compared to C. trachomatis infected cells alone (Figure 2A-C)
The effect of 405 nm irradiation on CCL2 production in C. trachomatis infected HeLa cells Due to the involvement of CCL2 with acute and chronic grades of chlamydial infections [13,29] and its association with a Th2-mediated response [30], we evaluated the effect of 405 nm photo treatment on its production
Summary
Chlamydia trachomatis is an intracellular bacterium that resides in the conjunctival and reproductive tract mucosae and is responsible for an array of acute and chronic diseases. One of the etiologic agents is the obligate intracellular bacterium Chlamydia trachomatis [2], which is the leading bacterial cause of sexually transmitted infections (STI) worldwide. These reproductive infections can lead to clinical symptoms such as urethritis, cervicitis, and pelvic inflammatory disease [3,4]. Due to repeated or persistent infections, or an absence of antibiotic treatment, ocular and reproductive tract sequelae can develop, resulting in corneal pacification and salpingitis respectively [4]
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