Effect of Different Irradiation Modes of Azulene-mediated Photodynamic Therapy on Singlet Oxygen and PGE2 Formation.

Abstract

Azulene samples in ethanol/distilled water (1, 10 and 100µm) were irradiated with a 638nm red laser (0.5 watts, light-to-target distance 2cm, energy density 4 or 40Jcm-2 ) by either continuous, fractionation or pulse mode. Singlet oxygen in the samples was measured using 10µm 9,10-dimethyl anthracene (positive control 10μm erythrosine) and relative fluorescence intensities were measured at 375/436nm excitation/emission. Peripheral blood mononuclear cells (PBMCs, 1×105 cells/well) preincubated with 0.01μgmL-1 rhTNF-α for 6h were cultured with irradiated azulene samples in RPMI-1640 under standard conditions. PGE2 was quantified by rhPGE2 ELISA kit using a Varioscan® microplate reader at an excitation wavelength of 420nm. Kruskal Wallis with Dunn`s test was performed at a significance level of P<0.05. The highest singlet oxygen amount was found in 10µm azulene samples irradiated at 40Jcm-2 under continuous mode (P=0.001 when compared with 10µm erythrosine). PGE2 expression in rhTNF-α-induced PBMCs was reduced to 45% of control by 1µm azulene irradiated at 40Jcm-2 under fractionation mode. Fractionation mode with intermediate laser energy density in the presence of low concentration of azulene could increase singlet oxygen and tend to reduce PGE2 .