Iodine released from the wound dressing Iodosorb modulates the secretion of cytokines by human macrophages responding to bacterial lipopolysaccharide.

Clinical data suggests that iodine released into the wound environment by Iodosorb may enhance the healing of chronic leg ulcers by a mechanism additional to its anti-bacterial activity. The macrophage is considered to play a central role in controlling wound healing and this study was designed to determine whether interaction with iodine could modulate macrophage cytokine output. The human macrophage cell line U937 was co-cultured with Iodosorb, Iodosorb conditioned medium or elemental iodine in the presence of optimal and sub-optimal stimulatory concentrations of bacterial lipopolysaccharide (LPS). The concentration of tumour necrosis factor-alpha (TNF alpha) and interleukin-6 (IL-6) were assayed in the culture medium after 24 hr culture. Co-culture with 0.25% Iodosorb, Iodosorb conditioned medium or 20 micrograms/ml iodine enhanced TNF alpha secretion (48 +/- 3% cytotoxicity in L929 bioassay to 78 +/- 2% cytotoxicity, +/-SD) by U937 cells stimulated with sub-optimal concentrations of LPS (0.25 ng/ml) and inhibited secretion of IL-6 from cells stimulated with 10 ng/ml LPS (> 750 pg/ml to 267 +/- 52 pg/ml, +/-SD, n = 4). Immunohistological staining of sections prepared from biopsies of chronic leg ulcers indicated that the majority of macrophages present were negative for TNF alpha. Thus one potential mechanism of action of iodine released from Iodosorb used as a wound dressing is to provide a pro-inflammatory stimulus in the wound tissue by activation of the resident macrophage population. This would result in a localized production of pro-inflammatory cytokines and generate an influx of monocytes and T-lymphocytes into the wound that may trigger the wound into a healing phase.