Platonin (4,4'-dimethyl-3,3'-di-n-heptyl-8-[2-(4-methyl-3-n-heptylthiazole)] -2,2'-dicarbocyanine diiodine) is one of the photosensitive trithiazolepentamethine cyanine dyes, with antioxidant, anti-inflammatory and anticancer activity. Platonin had also effects in rat models of endotoxemia which may have been mediated by a reduction of mean arterial blood pressure and inhibition of NO and free radical formation. Platonin inhibited the production of pyrogenic cytokines from human peripheral blood mononuclear cells (PBMC), resulting in antipyresis. Lipopolysaccharide (LPS) was shown to induce NF-kappaB activation of PBMC, and this effect was abolished by Platonin. Platonin is thus a potent macrophage-activating agent and immunomodulator. Platonin potently inhibited platelet aggregation and c-Jun NH2-terminal kinase (JNK) phosphorylation in collagen-activated platelets. The anti-aggregation effect did not affect bleeding time but increased occlusion time in platonin-treated mice. Platonin was potent in diminishing collagen- and Fenton reaction-induced ∙OH formation. Platonin exhibited remarkable neuroprotective properties against MCAO-induced ischemia in a mouse model through its antiaggregation, anti-inflammatory and antiradical properties.