Biomedical subjects

K Chrzan

Publications and source records attributed to K Chrzan.

3 recordsLinked to original sources

PubMed1987

Hydrogen peroxide formation and DNA base modification by tumor promoter-activated polymorphonuclear leukocytes.

This report shows that generation of hydrogen peroxide (H2O2) by human polymorphonuclear leukocytes (PMNs) activated with tumor promoters of varying potency as first and second stage promoters correlates well with activities of these promoters in vivo. Those tested were 12-O-tetradecanoylphorbol-13-acetate (TPA), a complete promoter, 12-O-retinoylphorbol-13-acetate (RPA), a synthetic TPA derivative almost devoid of first stage activity in some strains of mice, and mezerein (Mez), a potent second stage and much weaker first stage promoter. Mez-stimulated PMNs produced up to four times less H2O2, whereas RPA-stimulated PMNs produced up to 10 times less H2O2 than TPA-activated cells when used at concentrations between 0.5 and 15 nM to activate 7.5-8.5 X 10(4) PMNs/ml. Phorbol, a non-promoter, was totally inactive in this assay. Furthermore, the tumor promoter-activated PMNs caused formation of 5-hydroxymethyl-2'-deoxyuridine (HMdU) and thymidine glycol (dTG) in DNA co-incubated with those cells. The amounts of modified thymidines formed, particularly of HMdU, correlated well with first stage tumor promoting efficacy and with the amount of H2O2 that was generated by promoter activated PMNs. In comparison with TPA, Mez- or RPA-stimulated PMNs induced formation of 25 or 70% less H2O2 and 30 or 75% less HMdU, respectively, under conditions favoring HMdU formation. Thus, formation of either H2O2 by tumor promoter-stimulated phagocytes or HMdU in DNA exposed to those activated cells may serve as a measure of potency as a first stage tumor promoter. Formation of modified bases such as HMdU in DNA might constitute the genetic change imparted by the first stage tumor promoters.

DNA↗

PubMed1987

Chymotrypsin-specific protease inhibitors decrease H2O2 formation by activated human polymorphonuclear leukocytes.

Stimulated phagocytic cells generate active oxygen species which are known to contribute to inflammatory diseases, necrosis of surrounding tissues, mutagenicity and carcinogenicity. Until now, it was not certain whether protease inhibitors are capable of decreasing the production of those oxygen species, and if they are, what type of protease inhibitor is the most active. In this work we monitored formation of H2O2 by 12-O-tetradecanoylphorbol-13-acetate (TPA)-activated polymorphonuclear leukocytes (PMNs) because H2O2 is the immediate precursor of the actual damaging species. These determinations were carried out in the absence or presence of protease inhibitors and/or superoxide dismutase (SOD). The protease inhibitors tested were: potato inhibitors 1 (PtI-1) and 2 (PtI-2), a chymotrypsin-inhibitory fragment of PtI-2 (PCI-2), chicken ovoinhibitor (COI), turkey ovomucoid ovoinhibitor (TOOI), Bowman-Birk inhibitor (BBI), lima bean inhibitor (LBI) and soybean (Kunitz) trypsin inhibitor (SBTI). The order of activity, as measured by inhibition of H2O2 formation by TPA-activated PMNs during incubation at 37 degrees C for 30 min, was (in descending order): PtI-1 greater than or equal to PCI-2 greater than PtI-2 greater than COI greater than BBI greater than or equal to TOOI greater than LBI greater than SBTI. Thus, the most effective were the chymotrypsin-specific inhibitors PtI-1 and PCI-2, followed by the bifunctional inhibitors recognizing both chymotrypsin and trypsin, and the least active was SBTI, a predominantly trypsin inhibitor. At the higher concentrations of protease inhibitors tested, the inhibitory activity was similar in both the absence and presence of SOD. These results show that protease inhibitors specific for chymotrypsin but not those that are trypsin-specific are capable of inhibiting formation of active oxygen species during the oxidative burst of stimulated human PMNs.

Chymotrypsin↗

PubMed1986

Radiation-like modification of bases in DNA exposed to tumor promoter-activated polymorphonuclear leukocytes.

Oxygen species generated by human polymorphonuclear leukocytes (PMNs) activated by 12-O-tetradecanoylphorbol-13-acetate (TPA) caused the formation of 5-hydroxymethyl-2'-deoxyuridine (HMdUrd), and (+) and (-) diastereoisomers of cis-thymidine glycol (dTG) in DNA that was exposed to them. There were 9 HMdUrds and 31 dTGs formed per 1 X 10(6) thymidine residues. When Fe(II)/ethylenediaminetetraacetic acid was added to TPA-activated PMNs at 0, 10, 15, and 20 min after TPA, HMdUrd formation increased 5-, 13-, 30-, and 35-fold. Although dTG was initially formed in larger amounts than HMdUrd, it eventually decreased but was still 5-, 6-, 5.5-, and 3-5-fold, respectively, higher than in the absence of iron. From 65 to 1800 times more HMdUrd was formed in DNA when autologous plasma was present during incubation of DNA with TPA-activated PMNs than in its absence. The levels of dTG also varied from about the same as HMdUrd to the nondetectable. Reconstituted human serum transferrin used instead of plasma or Fe(II) also supported the formation of HMdUrd and dTG. When DNA was treated with Fe(II)-reduced H2O2 in the absence of PMNs and TPA, both derivatives were formed. However, the same treatment of marker dTG of dTG-containing polydeoxyadenylic-thymidylic acid caused the decomposition of dTG. Thus, the reduction of hydrogen peroxide by Fe(II) complexed to either ethylenediaminetetraacetic acid or amino acids amy be responsible for the formation of HMdUrd and dTG and for subsequent decomposition of dTG in DNA exposed to the TPA-activated PMNs.

DNA↗