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In vitro evaluation of the antimicrobial, anti-oxidative, anti-inflammatory and apoptosis-regulating effects of
Samuel Devine1, Domenico Santoro2
1Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, 2015 SW 16th Ave, Gainesville, FL, 32610, USA.
Background:
Antimicrobial resistance complicates the treatment for skin/ear infections caused by Staphylococcus pseudintermedius (SP), Staphylococcus coagulans (SC), Pseudomonas aeruginosa (PA), and Malassezia pachydermatis (MP). This highlights the need for novel therapeutic options and improved antimicrobial stewardship. Retinoids are known for their anti-inflammatory and kerato-regulatory effects. Retinaldehyde has been suggested to possess also antimicrobial activity.
Objective:
To evaluate the antimicrobial, anti-inflammatory, antioxidative, and apoptosis-regulating effects of retinaldehyde.
Methods:
Six two-fold dilution of retinaldehyde were tested against clinical isolates of SP (n = 30), SC (n = 30), PA (n = 10), and MP (n = 30) using microbroth dilution. Both the minimum inhibitory (MIC) and bactericidal/fungicidal (MBC/MFC) concentrations were determined. Immortalized canine keratinocytes were treated with retinaldehyde (5, 50 and 500 µg/mL) with or without tumor necrosis factor α (TNFα) for 24 h. Then interleukin (IL)-1β, IL-8, malondialdehyde, and caspase-3 activity were quantified by ELISA.
Results:
Retinaldehyde exhibited antimicrobial activity with median MIC/MBC values of 8 µg/mL for SP and SC, and 32 µg/mL for MP. For PA, retinaldehyde had inhibitory and bactericidal properties at 64 µg/mL for only 2/10 isolates. Retinaldehyde significantly reduced TNFα-induced IL-8 secretion (p < 0.0001) without affecting MDA levels. Levels of IL-1β were undetectable. Retinaldehyde modulated apoptosis in a dose-dependent manner. In TNFα-stimulated cells, 50 µg/mL and 500 µg/mL reduced caspase-3 activity, whereas 5 µg/mL increased apoptosis in unstimulated cells.
Conclusions:
These findings demonstrate that retinaldehyde possesses antimicrobial and immunomodulatory effects in vitro, supporting its potential as a topical adjunct therapy for canine dermatological infections, particularly at 500 µg/mL. Further stability studies and clinical trials are needed to confirm these results.
Insights
Retinaldehyde shows antimicrobial and anti-inflammatory effects against common canine skin pathogens. This suggests its potential as a topical treatment for dermatological infections, particularly at higher concentrations.
Area of Science:
- Veterinary Dermatology
- Microbiology
- Pharmacology
Background:
- Antimicrobial resistance in canine skin/ear infections necessitates novel therapeutics.
- Retinoids, including retinaldehyde, have anti-inflammatory and kerato-regulatory properties.
- Retinaldehyde may possess antimicrobial activity.
Purpose of the Study:
- To evaluate the antimicrobial effects of retinaldehyde against key canine pathogens.
- To assess the anti-inflammatory, antioxidative, and apoptosis-regulating properties of retinaldehyde.
- To determine the potential of retinaldehyde as a therapeutic agent for canine dermatological conditions.
Main Methods:
- Microbroth dilution determined minimum inhibitory (MIC) and bactericidal/fungicidal (MBC/MFC) concentrations of retinaldehyde against Staphylococcus pseudintermedius, Staphylococcus coagulans, Pseudomonas aeruginosa, and Malassezia pachydermatis.
- Immortalized canine keratinocytes were treated with retinaldehyde (5, 50, 500 µg/mL) with or without TNFα.
- Quantification of IL-1β, IL-8, malondialdehyde, and caspase-3 activity via ELISA.
Main Results:
- Retinaldehyde demonstrated antimicrobial activity against SP, SC (median MIC/MBC: 8 µg/mL), and MP (median MIC/MBC: 32 µg/mL).
- Activity against PA was observed at 64 µg/mL for limited isolates.
- Retinaldehyde significantly reduced TNFα-induced IL-8 secretion and modulated apoptosis in a dose-dependent manner, reducing caspase-3 activity in stimulated cells at higher concentrations.
Conclusions:
- Retinaldehyde exhibits in vitro antimicrobial and immunomodulatory effects.
- These findings support retinaldehyde's potential as a topical adjunct therapy for canine dermatological infections.
- Further research, including stability studies and clinical trials, is warranted.
