The effect of hematoporphyrin and light on human platelets. 3. Release of potassium and acid phosphatase

The effect of chlorin e₆ drug on platelet aggregation activity

The goal of the study is to evaluate the effect of Radachlorin (OOO “RADA-PHARMA”, Russia) (RC) on platelet aggregation in ex vivo and in vivo experiments. The experiments were conducted on male Wistar rats. Platelet aggregation activity was determined in platelet-rich plasma (PRP) using a turbidimetric method and the aggregation inducer was ADP at a final concentration of 1.25 μM. PRP samples containing RC were irradiated with ALOD-Granat laser device (OOO “Alkom Medika”, Russia) at 662 nm wavelength with 0.05 W/cm2 power density. After a 5-minute incubation of PRP with RC in the dark, dose-dependent inhibition of platelet aggregation was observed. Laser irradiation (12.5 J/cm2 and, especially, 25 J/cm2) increased the inhibitory effect of RC. 3 hours after intravenous administration of RC, the rate and intensity of platelets aggregation did not change, while disaggregation slowed down significantly. Irradiation at a dose of 5 J/cm2 did not affect the platelets aggregation kinetics, and disaggregation slowed down even more at 10 J/cm2, and at 20 J/cm2 the rate and intensity of platelets aggregation decreased, and no disaggregation occurred.

In vitro, RC inhibited the ADP-induced platelet aggregation in rats in a dose-dependent manner; after laser irradiation, this effect was enhanced significantly. The effect of RC on circulating platelets leads to a change in their functional state, which manifests in slowing down the disaggregation after exposure to ADP. After laser irradiation (10 J/cm2 and, especially, 20 J/cm2), the severity of the functional changes increases. The role of decreasing the disaggregation activity of platelets in the mechanism of vascular thrombosis in the affected area of photodynamic therapy (PDT) is discussed.

Platelet injury during phototherapy

Phototherapy with blue fluorescent light is widely employed for treatment of neonatal hyperbilirubinemia. Functional, biochemical, and morphologic changes produced by blue fluorescent light in human platelets were identified and characterized. Platelet-rich plasma was exposed for up to 170 min to amounts of light equivalent to that used in phototherapy of neonatal hyperbilirubinemia. Within 110 min of light exposure, platelets were essentially no longer aggregable by ADP and connective tissue suspension and were depleted of ADP, ATP, and glycogen. Electron photomicrographs revealed these platelets to be swollen, depleted of glycogen granules and organelles, and to have ill-defined membranes. Platelet injury could be accelerated by adding a photosensitizing agent, hematoporphyrin, to platelet samples before exposure. In contrast, control platelets kept in the dark for 170 min or nonirradiated platelets resuspended in irradiated plasma maintained their integrity. The results indicate that platelets are damaged in vitro when exposed to amounts of blue light used in phototherapy.