Promoting effect of acylated homoserine lactone on the healing of tissue damage in model rats with incontinence-associated dermatitis

OBJECTIVE

One of the most common complications in patients with incontinence is incontinence-associated dermatitis (IAD). This study was conducted to determine the pathophysiology of the healing process of IAD and to develop an effective therapeutic approach according to its pathophysiology.

METHOD

IAD was reproduced on a dorsal rat skin by applying agarose gel containing water and enzymes, and inoculating it with bacteria. Examination of the IAD healing process suggested that the promotion of keratinocyte migration and improvement of basement membrane enhance keratinocyte layer elongations, which contribute to IAD healing. A therapeutic approach using N-(3-oxotetradecanoyl)-L-homoserine lactone, which is one of the acylated homoserine lactones (AHLs) and can promote keratinocyte migration in vitro, was applied on the IAD area in rats.

RESULTS

AHL treatment after IAD development resulted in an earlier tipping point for recovery than the vehicle treatment. Histological and immunohistological analyses revealed that the tissue surface was already covered by the epidermis, indicating the results of elongation of the keratinocyte layer from hair follicles. The characteristics of the alignment of basal keratinocytes, the existence of stratum corneum, and the membrane-like distribution of the components of basement membrane were similar to those of a normal epidermis.

CONCLUSION

These results suggested that AHL application possibly contributed to earlier IAD healing before progressing to a severe state. Although elongation of the keratinocyte layer was observed in both the AHL and vehicle groups, the possibility that AHL application promotes IAD healing was suggested. The new concept of the enhancement of keratinocyte migration as a therapeutic approach for IAD would change the skin care strategy for IAD in the healthcare setting.

Gene Flow Across Genus Barriers - Conjugation of Dinoroseobacter shibae's 191-kb Killer Plasmid into Phaeobacter inhibens and AHL-mediated Expression of Type IV Secretion Systems

Rhodobacteraceae harbor a conspicuous wealth of extrachromosomal replicons (ECRs) and therefore the exchange of genetic material via horizontal transfer has been supposed to be a major evolutionary driving force. Many plasmids in this group encode type IV secretion systems (T4SS) that are expected to mediate transfer of proteins and/or DNA into host cells, but no experimental evidence of either has yet been provided. Dinoroseobacter shibae, a species of the Roseobacter group within the Rhodobacteraceae family, contains five ECRs that are crucial for anaerobic growth, survival under starvation and the pathogenicity of this model organism. Here we tagged two syntenous but compatible RepABC-type plasmids of 191 and 126-kb size, each encoding a T4SS, with antibiotic resistance genes and demonstrated their conjugational transfer into a distantly related Roseobacter species, namely Phaeobacter inhibens. Pulsed field gel electrophoresis showed transfer of those replicons into the recipient both individually but also together documenting the efficiency of conjugation. We then studied the influence of externally added quorum sensing (QS) signals on the expression of the T4SS located on the sister plasmids. A QS deficient D. shibae null mutant (ΔluxI₁) lacking synthesis of N-acyl-homoserine lactones (AHLs) was cultivated with a wide spectrum of chemically diverse long-chain AHLs. All AHLs with lengths of the acid side-chain ≥14 reverted the ΔluxI₁ phenotype to wild-type. Expression of the T4SS was induced up to log2 ∼3fold above wild-type level. We hypothesize that conjugation in roseobacters is QS-controlled and that the QS system may detect a wide array of long-chain AHLs at the cell surface.