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In this study, we investigated natural vascular scaffolding (NVS) treatment on vascular functionality using freshly isolated human popliteal arteries in vitro. Arteries were exposed to intraluminal NVS treatment consisting of a compound (4 amino-1,8-naphthalimide) photoactivated by a 450-nm light-emitting light fiber placed inside the artery. This procedure results in covalent linking between the extracellular matrix proteins to achieve a larger vessel diameter post-angioplasty and minimizing elastic recoil. Immediately following NVS treatment, rings were cut from the treated arteries and mounted in organ baths for contractility testing in response to U46619 and sodium nitroprusside. We also investigated the effect of NVS treatment on IL-6 cytokine release from vascular rings following a 4-h organoculture post-NVS treatment. Based on our results, we conclude that exposure of the vessels to NVS treatment does not adversely affect the contractile responsiveness of the vascular smooth muscle and exerts no pro-inflammatory effect. Graphical abstract.

A major disadvantage of conventional phototherapy is the requirement for the in situ delivery of stimulating photoenergy subsequent to the binding of photochemicals to target malignant cells, or virus-infected cells, or viruses. This drawback has resulted in considerable limitation in the use of photochemicals in photomedicine. To circumvent this problem, we have investigated the antiviral efficacy of a brominated 1,8-naphthalimide photocompound, termed LY66Br [3-bromo-4-(hexylamino)-N-hexyl-1,8-naphthalimide], which upon exposure to visible light at 420 nm generates independently of oxygen one or more stable antiviral molecular photoproducts (e.g., is 'preactivated'). Human cell lines infected with the human immunodeficiency virus type 1 (HIV-1), or with the human T-lymphotropic virus type-1 (HTLV-I) exposed to photochemical products of LY66Br (P-LY66Br) completely lost their ability to form syncytia in vitro. Photoproducts of P-LY66Br retain full antiviral activity for at least 3 and 6 weeks when stored at room temperature and at -80 degrees C, respectively. Concentrations of P-LY66Br, effective in inhibiting syncytium formation mediated by HIV-1 and HTLV-I, were nontoxic to normal red cell components of whole blood (red blood cell 2,3-diphosphoglyceric acid, adenosine triphosphate, osmotic fragility or blood type antigens). Additionally, no evidence of acute toxicity was demonstrated in mice following an intravenous bolus inoculation to achieve plasma concentration of 600 microM of P-LY66Br. These findings represent the first demonstration of inhibition of retrovirus-induced syncytium formation by a photochemical product, and justify further investigation of the preactivation process of photochemicals in the treatment of systemic viral infections such as the acquired immunodeficiency syndrome (AIDS), in cancer therapy, and in sterilization of banked blood products.

The antiviral property of a newly designed class of 1,8-naphthalimide photochemical compounds was investigated. One such photoactive compound, 1,14-bis-(N-hexyl-3'-bromo-1,8'-naphthalimide-4'-yl)-1,4,11,14- tetraazatetradecane-5,10-dione (diED66Br), when activated to an excited state by visible light (420 nm), effectively neutralized the in vitro infectivity of human immunodeficiency virus (HIV-1). Light-activated diED66Br also inhibited syncytium formation induced by cells infected with HIV-1. Nonactivated diED66Br was completely ineffective. The neutralizing and syncytium-inhibiting doses of activated diED66Br had no effect on normal human peripheral blood mononuclear cells. Radioimmunoprecipitation analysis indicated that diED66Br neutralizing activity resulted primarily from its ability to inhibit the binding of HIV-1 envelope glycoprotein gp120 to the CD4 cellular receptors. Although the exact molecular mechanism of viral neutralization by diED66Br has not been elucidated, its ability to neutralize HIV-1 infectivity and to inhibit syncytium formation supports further investigations of this photochemical as a potential therapeutic treatment of HIV-1 infection.