Topical Application of Cinnamaldehyde Promotes Faster Healing of Skin Wounds Infected with Pseudomonas aeruginosa.

Wound healing can be delayed following colonization and infection with the common bacterium Pseudomonas aeruginosa. While multiple therapies are used for their treatment, these are ineffective, expensive, and labour-intensive. Thus, there is an enormous unmet need for the treatment of infected wounds. Cinnamaldehyde, the major component of cinnamon oil, is well known for its antimicrobial properties. Herein, we investigated the effects of sub-inhibitory concentrations of cinnamaldehyde in the virulence of P. aeruginosa. We also assessed its healing potential in P. aeruginosa-infected mouse skin wounds and the mechanisms involved in this response. Sub-inhibitory concentrations of cinnamaldehyde reduced P. aeruginosa metabolic rate and its ability to form biofilm and to cause haemolysis. Daily topical application of cinnamaldehyde on P. aeruginosa-infected skin wounds reduced tissue bacterial load and promoted faster healing. Lower interleukin-17 (IL-17), vascular endothelial growth factor (VEGF) and nitric oxide levels were detected in cinnamaldehyde-treated wound samples. Blockage of transient receptor potential ankyrin 1, the pharmacological target of cinnamaldehyde, abrogated its healing activity and partially reversed the inhibitory actions of this compound on VEGF and IL-17 generation. We suggest that topical application of sub-inhibitory concentrations of cinnamaldehyde may represent an interesting approach to improve the healing of P. aeruginosa-infected skin wounds.

Cinnamaldehyde modulates LPS-induced systemic inflammatory response syndrome through TRPA1-dependent and independent mechanisms.

Cinnamaldehyde is a natural essential oil suggested to possess anti-bacterial and anti-inflammatory properties; and to activate transient receptor potential ankyrin 1 (TRPA1) channels expressed on neuronal and non-neuronal cells. Here, we investigated the immunomodulatory effects of cinnamaldehyde in an in vivo model of systemic inflammatory response syndrome (SIRS) induced by lipopolysaccharide. Swiss mice received a single oral treatment with cinnamaldehyde 1 h before LPS injection. To investigate whether cinnamaldehyde effects are dependent on TRPA1 activation, animals were treated subcutaneously with the selective TRPA1 antagonist HC-030031 5 min prior to cinnamaldehyde administration. Vehicle-treated mice were used as controls. Cinnamaldehyde ameliorated SIRS severity in LPS-injected animals. Diminished numbers of circulating mononuclear cells and increased numbers of peritoneal mononuclear and polymorphonuclear cell numbers were also observed. Cinnamaldehyde augmented the number of peritoneal Ly6C(high) and Ly6C(low) monocyte/macrophage cells in LPS-injected mice. Reduced levels of nitric oxide, plasma TNFα and plasma and peritoneal IL-10 were also detected. Additionally, IL-1ß levels were increased in the same animals. TRPA1 antagonism by HC-030031 reversed the changes in the number of circulating and peritoneal leukocytes in cinnamaldehyde-treated animals, whilst increasing the levels of peritoneal IL-10 and reducing peritoneal IL-1ß. Overall, cinnamaldehyde modulates SIRS through TRPA1-dependent and independent mechanisms.