Cell experiment:

HeLa cell line (human cervical cancer cells) is cultured in DMEM supplemented with 10% fetal bovine serum (FBS), L-glutamine (300 mg/L), penicillin (100 U/ml) and streptomycin(100 μg/ml) at 37℃ in 5% CO2. HT-29 cell line (human colorectal adenocarcinoma) is cultured in RPMI supplemented with 10% fetal bovine serum (FBS), L-glutamine (300 mg/L), penicillin (100 U/mL) and streptomycin (100 μg/mL) at 37℃ in 5% CO2. The cells are split every second day to keep the cell growth in logarithmic phase. The cells are routinely tested for mycoplasma. The cells are treated with different concentrations of TPCK or TLCK (5, 10, 25, 50, 100, 150, and 200 μM) for 30 min and/or with different concentrations of IFN-γ for 2 h followed by treatment with different concentrations of anti-Fas for 2 or 4 days for each specific experiment. The control cells are treated with the respective vehicle only. Cell viability analysis of HeLa and HT-29 cells is assessed by their XTT reduction activity. 100 μL of 2×104 cells/mL is incubated with treatments at the indicated time. At the end of the incubation period, 25 μL of 1 mg/mL XTT solution (containing 0.2 mM phenazine methosulphate (PMS) is added and the cells are incubated for an additional 1 h. The OD values are measured using an ELISA reader at 450 nm with a reference wavelength of 650 nm[1].

Tosyllysine Chloromethyl Ketone (hydrochloride) is a protease inhibitor [1][2][3].

L-1-chloro-3-[4-tosylamido]-7-amino-2-heptanone-HCl (TLCK) is a protease inhibitor. TLCK is an active site-directed agent that inhibits serine proteinases with trypsin-like activity. TLCK also interacts non-selectively with thiol groups and thereby inhibits cysteine proteinases and other enzymes. In LPS-activated rat alveolar macrophages, TLCK at 1-100 μM inhibited NOx- accumulation and inducible iNOS expression in a concentration-dependent way [1]. To prevent proteolytic degradation, TLCK may be used in protein purification protocols [2]. TLCK significantly increased the cytotoxic activity of C. histolyticum supernatant towards human epithelial HeLa cells probably by hindering natural defence mechanisms of cells. 30 min incubation with bacterial supernatant increased toxicity in both concentrations (200 and 1000 μM) from 18 ± 3% to 39 ± 3% and 57 ± 8%, respectively. TLCK also blocked clostripain enzymatic activity obtained from C. histolyticum. So TLCK might be used to treat diseases complicated by concurrent C. histolyticum infection [3].

References:
[1].  Griscavage JM, Wilk S, Ignarro LJ. Serine and cysteine proteinase inhibitors prevent nitric oxide production by activated macrophages by interfering with transcription of the inducible NO synthase gene. Biochem Biophys Res Commun. 1995 Oct 13;215(2):721-9.
[2].  Urban MK, Franklin SG, Zweidler A. Isolation and characterization of the histone variants in chicken erythrocytes. Biochemistry. 1979 Sep 4;18(18):3952-60.
[3].  Józwiak, J.,Komar, A.,Jankowska, E., et al. Determination of the cytotoxic effect of Clostridium
histolyticum culture supernatant on HeLa cells in the presence of protease inhibitors.  FEMS Immunology & Medical Microbiology 45(2):137-42 (2005).