Fig. 7: Combined inhibition of cathepsin G and elastase suppresses activation of all IL-36 subfamily cytokines by neutrophil proteases.

HeLa^IL-36R-SEAP cells were stimulated with a combination of recombinant human IL-36 proteins (IL-36α + β + γ, all 500 pM final) pre-incubated for 2 h at 37 °C with a titration of PMA-activated human neutrophil degranulate, or control unstimulated neutrophil S/N 1:4, in the presence or absence of a fixed concentration (5 μM) of the best novel candidate cathepsin G (z-EPF-cmk) and elastase (z-API-cmk) peptide inhibitors either alone or in combination, as indicated. After 24 h, cytokine concentrations in the culture supernatants were determined by ELISA. Results shown are representative of at least three independent experiments. Error bars represent the mean ±SEM of triplicate determinations from a representative experiment. Asterisk(s) indicate significance levels, ***p < .0001, **p < .001, *p < .1, by Student’s t test. ND not detected, indicates where cytokine production was below the detection threshold of the assay