Low-Nanomolar Chetomin in Human Skin Cells: Preserved Viability and Wound Closure, Reduced Basal IL-6 and IL-1β Release, and Preliminary Tolerability in Galleria mellonella

Chetomin is a disulfide-bridged epipolythiodioxopiperazine produced by Chaetomium endophytes and is studied mainly as an inhibitor of the HIF-1α-p300 interaction in tumour models. Its behaviour in non-transformed skin cells at sub-toxic concentrations has not been reported. We exposed HaCaT keratinocytes and HFF-1 fibroblasts to 2.5-20 nM chetomin and recorded viability (MTT and PrestoBlue, 24 and 72 h), scratch wound closure, basal IL-6 and IL-1β release (ELISA), collagen I and III immunostaining, real-time impedance over 87.7 h, and survival of Galleria mellonella larvae. Viability remained at or above 97% of control at 24 h in both lines. At 72 h, HaCaT values ranged from 101 to 107% (MTT) and 112 to 116% (PrestoBlue), whereas HFF-1 values rose to 128-143% (MTT) and 118-125% (PrestoBlue). Scratch closure in HaCaT was indistinguishable between groups; in HFF-1, closure at 10 nM followed the control curve, while 15 and 20 nM closed significantly less by 36 h. IL-6 in untreated HFF-1 supernatants was 290 pg/mL and fell to 45-78 pg/mL under chetomin, against 1310 pg/mL after H 2 O 2 ; IL-1β followed the same direction in both lines. Impedance confirmed unchanged growth at 2.5 nM and reduced cell index at 5 and 10 nM in HFF-1. All larvae injected with 50 or 100 nM survived six days. Chetomin is therefore biologically active in skin cells at concentrations one to two orders of magnitude below its reported antitumour range, without measurable loss of viability. The present data are descriptive; the mechanism was not investigated and no inflammatory challenge or wound model was applied, so any wound-healing relevance remains to be established.