Vascular alterations after photodynamic therapy mediated by 5-aminolevulinic acid in oral leukoplakia.

Impairment of vascular functions after photodynamic therapy (PDT) is frequently associated with tumor remission and is considered one of the main antineoplastic PDT effects. Vascular alterations in oral leukoplakia (OL) treated with PDT have not yet been described. The aim of this study was to evaluate the effect of topical 5-ALA-mediated PDT on the vascular network of 4NQO-induced OL in rats. After applying 4NQO topically on the tongue during 16 weeks, there was induction of dysplastic lesions, which were treated with two PDT sessions (with an interval of 72 h between them), using topical application of 5-ALA and posterior irradiation with a laser (90 J/cm2 fluency). Histological sections of the tongues were obtained and analyzed concerning plasmatic exudation and microvessel density after immunolabeling with CD31 and CD34 vessel markers. There was intense plasmatic exudation after 6 h of the first PDT session; at 6 h of the second PDT session, there was a significant reduction in the density of CD31- and CD34-positive microvessels in comparison to controls (p < 0.05). In the PDT intervals, there was an increase in the density of CD31 and CD34 microvessels, suggesting angiogenesis. Topical application of 5-ALA-mediated PDT caused an immediate deleterious effect on the vascular network, increasing vessel permeability and reducing vessel density, mainly after two sessions of the treatment. However, secondary angiogenesis emerged in these lesions during intervals of the PDT session. This fact may be considered during the adoption of a PDT protocol, to avoid OL resistance and recurrence after the treatment.

Effect of 5-ALA-mediated photodynamic therapy on mast cell and microvessels densities present in oral premalignant lesions induced in rats.

Acute inflammatory response after photodynamic therapy is frequently described, and increase on mast cell degranulation is also present during this process. The mast cell activation may improve angiogenesis, and this fact has been associated with progression of oral premalignant lesions (OPL). The aim of this study was to evaluate whether photodynamic therapy (PDT) increases mast cell density (MCD) and microvessels density (MVD) in 4-nitroquinoline-1-oxide(4NQO)-induced OPL in rats. 4NQO-induced OPL were treated or not with 5-ALA followed by laser irradiation (PDT group and 4NQO groups, respectively). Mast cells and CD34+ microvessels were counted. Both PDT and 4NQO groups had MCD and MVD that were higher than normal mucosa (p b 0.05). The 4NQO group had the lowest number of non-degranulated MCD in comparison to experimental periods of PDT (PDT 6 h ­ p=0.020; 24 h ­ p=0.016; 48 h ­ p=0.003; 72 h ­ p=0.033). Only in the PDT group did MCD and MVD have a significant correlation (r= 0.6219, p = 0.010). 5-ALA-mediated PDT modified the MCD and MVD in the induced OPL, leading to degranulation of mast cells and angiogenesis. A PDT protocol with an efficient eradication of the OPL must be adopted considering the angiogenesis potential associated with the mast cell activation after the therapy.