Glycyrrhizin Reduces HMGB1 and Bacterial Load in Pseudomonas aeruginosa Keratitis

Abstract

PurposeHigh mobility group box 1 (HMGB1) contributes to poor disease outcome in Pseudomonas aeruginosa keratitis. This study tests the prophylactic effect of treatment with HMGB1 inhibitors, glycyrrhizin (GLY) and its derivative, carbenoxolone (CBX), for Pseudomonas keratitis.MethodsWe treated C57BL/6 (B6) mice subconjunctivally with GLY or CBX, infected with a noncytotoxic clinical isolate (KEI 1025) or a cytotoxic strain (ATCC 19660) of P. aeruginosa, and injected intraperitoneally with either agent. Clinical score, photography with a slit lamp, real-time RT-PCR, ELISA, myeloperoxidase (MPO) assay, bacterial plate count, histopathology, and absorbance assays were used to assess treatment efficacy and bacteriostatic activity.ResultsAfter KEI 1025 infection, GLY treatment reduced HMGB1 (mRNA and protein levels) and improved disease outcome with significant reduction in mRNA levels of IL-1β, TLR4, CXCL2, and IL-12; protein expression (IL-1β, CXCL2); neutrophil infiltrate; and bacterial load. Treatment with GLY enhanced antimicrobial proteins, including CRAMP and mBD2, but not mBD3. Glycyrrhizin also reduced clinical scores and improved disease outcome in corneas infected with strain 19660. However, neither HMGB1 mRNA or protein levels were reduced, but rather, CXCL2 expression (mRNA and protein), neutrophil infiltrate, and bacterial load were reduced statistically. Treatment with GLY initiated 6 hours after infection reduced plate count; GLY also was bacteriostatic for KEI 1025 and ATCC 19660.ConclusionsGlycyrrhizin reduces HMGB1 and is protective against P. aeruginosa–induced keratitis with a clinical isolate that is noncytotoxic. It was similar, but less effective when used after infection with a cytotoxic strain, which did not reduce HMGB1.

Glycyrrhizin, a High-Mobility Group Box 1 Inhibitor, Improves Lipid Metabolism and Suppresses Vascular Inflammation in Apolipoprotein E Knockout Mice

“…The effects of GLY have been investigated in a wide range of diseases, such as rat myocardial ischemia/reperfusion-induced injury, intracerebral hemorrhage, and Pseudomonas aeruginosa keratitis. The indicated studies confirmed that GLY is a potent HMGB1 inhibitor [38-40]. Consistent with the results of these studies, in this study, we showed that GLY had inhibitory effects on HMGB1 expression and release.…”

Glycyrrhizin Use for Multi-Drug Resistant Pseudomonas aeruginosa: In Vitro and In Vivo Studies

“…This trend in antibiotic resistant bacterial infections is of serious global concern, fueled by the lack of effective antibiotics available and few being developed. 3 GLY, derived from Glycyrrhiza glabra, is antimicrobial and anti-inflammatory 6 ; it has many additional effects 6 and has shown promise against non-MDR isolates 7,8,16,19,20 and our current work shows it is effective against MDR isolates. Clinically, GLY also has been successfully used to treat blepharitis 28 and hepatitis patients 29,30 with no toxicity.…”

“…In past work, we never observed different GLY MICs when testing several non-MDR clinical isolates. 7,19,20 We also tested the MIC of ciprofloxacin, to which MDR9 is resistant and found an MIC of 32 lg/mL. The MIC for GLY together with ciprofloxacin showed that GLY reduced ciprofloxacin MIC 2fold, suggesting that less antibiotic could be used for treatment.…”

“…14,15 GLY reduces proinflammatory mediators and has direct antimicrobial effects, reducing plate count after corneal infection with a non-MDR clinical (keratitis) PA isolate, KEI 1025 by~4.5 logs. 7 In addition, GLY has been shown to enhance the bioavailability of drugs, including antibiotics, 16,17 making them more effective at lower concentrations. Lower bacterial membrane permeability, overexpression of efflux pumps, biofilm, and antibiotic inactivating enzymes are major contributors to intrinsic multidrug resistance in PA. 18 Thus, the objectives of this study are to test GLY (with/without ciprofloxacin), and its effects on several of these contributors to resistance in MDR PA isolates from systemic and ocular sources.…”

Bacterial keratitis: Photodynamic inactivation reduced experimental inflammation

“…Concomitant, heavy cellular infiltrates are identified in the anterior chamber, which is also called the hypopyon. Typically, in the later stages corneal ulcers occur (18). Corneal ulcers are estimated to cause approximately two million new cases of monocular blindness every year (1).…”