Secretion of IL-6 by fibroblasts exposed to Australian honeys involves lipopolysaccharide and is independent of floral source

Abstract

Honey stimulates cellular secretion of cytokines, which has been attributed to activation of lipopolysaccharide (LPS)-dependent and LPS-independent pathways. The objective of this study was to identify whether LPS is present in Australian honey samples at levels that can stimulate interleukin-6 (IL-6) secretion by fibroblasts and whether it can transduce cell signalling by activating toll-like receptor 4 (TLR4). IL-6 was measured in culture media of fibroblasts exposed to honey for 24 h. LPS was detected in a 0.125 mg/mL solution of grey ironbark honey (0.61 ± 0.05 ng/g honey). TLR4 signalling was observed in RAW264.7 macrophages that were exposed to honey and this was prevented by preincubating the honey with the LPS-neutralising agent, polymyxin B. Australian Eucalyptus, Leptospermum and Cyathode honeys stimulated IL-6 secretion in cultured human dermal fibroblasts. To examine whether the response was dependent on floral source, fibroblasts were exposed to four different samples of grey ironbark honey obtained from Queensland and New South Wales, Australia. The magnitude of the cytokine response to these honeys was highly varied. We conclude that Australian honeys contain endotoxin at levels that can stimulate IL-6 secretion by fibroblasts and that signalling in macrophages involves TLR4 activation. The IL-6 secretory response was independent of floral source.

Honey and propolis for wound healing

“…Collagen formation: With topical honey dressing, the low pH could help to create and maintain optimal conditions for fibroblasts activities, such as migration and the organization of collagen where, honey 77 and propolis 2,10 increases migration and proliferation of fibroblasts to the wound enhancing collagen types I and III expression and degradation in wounds matrix. 64 As flavonoids can promote the synthesis of collagen, 2 the fibroblasts that are responsible for the replacement of fibrin clot with scar tissue, slowing the angiogenesis and changing the collagen composition 78 resulting in favorable biochemical environment leading to re-epithelization.…”

“…In addition to their role in extracellular matrix production and scar tissue formation, fibroblasts release cytokines to provide regulatory control over immune cell function. 77 Moreover, flavonoids increase vascularization and protect the vascular endothelium. 23 It was found that propolis can decrease scar formation, shorten healing time, boost wound contraction, accelerate tissue repair, and ultimately improve patients' quality of life in skin wound healing.…”