Stimulation of Human Platelet Cytotoxicity by Various Activators in the Absence of Antibodies: Release of Thromboxane A2 and Soluble Cytotoxic Factors. Purification and Partial Characterisation of 14 and 28 kDa Cytotoxic Proteins.
The cytolytic activity of human plasma free platelets treated with various stimulators (Ca-ionophore, PAF (platelet activating factor), PHA, and ricin) has been studied on human erythroid leukemia cell line (K562). The 14 kDa and 28 kDa platelet cytotoxic factors (PCF) have been purified from the supernatant obtained from platelets stimulated by 10(-7) M Ca-ionophore. The PCF-14 N-terminal sequence ((1)YAPQXQFGP(9)-) appeared to be homologous to the region 241-249 residues of the human C1s complement component. The PCF-28 N-terminal sequence (DVGLT-) did not display any homology to known human proteins. The PCF-14 and the PCF-28 have been detected both in the supernatants of platelets treated with various stimulators (10(-7) M Ca-ionophore A23187, or 10(-8) M PAF, or 10(-9) M PHA, or 10(-13) M ricin) and in the extracts of disrupted platelets treated by these stimulators. All of these stimulators enhanced the production of thromboxane A(2) by platelets, as evidenced from the accumulation of thromboxane B(2), a spontaneous hydrolysis product of thromboxane A(2). These results indicate that platelet cytotoxicity to the K562 cells and the release of PCF-14 and PCF-28 might be mediated by the stimulation of thromboxane A(2) synthesis, when platelets have been activated through the cycloxygenase pathway.
Paromov
Victor M.
VM
Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.
Bughlava
Samira
S
Malakhova
Natalia V.
NV
Kiselevsky
Michail V.
MV
Dolgikh
Dmitry A.
DA
Kirpichnikov
Mikhail P.
MP