Photoactivated Hypericin is an Anti-Proliferative Agent that Induces a High Rate of Apoptotic Death of Normal, Transformed, and Malignant T Lymphocytes: Implications for the Treatment of Cutaneous Lymphoproliferative and Inflammatory Disorders

Abstract

Hypericin is a photodynamic compound activated by either visible (400-700 nm) or UVA (320-400 nm) light, and has been shown to inhibit the growth of a variety of neoplastic cell types. In this study, hypericin was found to inhibit proliferative responses of malignant T cells derived from the blood of patients with cutaneous T cell lymphoma. Control cells included peripheral blood mononuclear cells (PBMC) from normal volunteers or Epstein-Barr virus-transformed lymphocytes. Cells from each of these populations were incubated with serial dilutions of hypericin or 8-methoxypsoralen and then stimulated with the mitogen ConA (10 microg per ml). Cultures were prepared in the dark to minimize photoactivation of the hypericin. Proliferation was measured by [3H]thymidine labeling after 72 h. Hypericin, photoactivated with 1.1-3.3 J white light per cm2, inhibited cellular proliferation of malignant T cells with IC50 values from 0.34 to 0.53 microM, normal PBMC with IC50 values of 0.11-0.76 microM, and Epstein-Barr virus-transformed cells with IC50 values of 0.75-3.2 microM. UVA-photoactivated hypericin (0.5-2.0 J per cm2) could also inhibit proliferation with IC50 values of 0.57-1.8 microM, 0.7-4.6 microM, and 2.0-3.7 microM for malignant, normal, or Epstein-Barr virus-transformed cells, respectively. Hypericin, photoactivated with either UVA or white light, could induce near complete apoptosis (94%) in malignant cutaneous T cell lymphoma T cells, whereas lower levels of apoptosis (37-88%) were induced in normal PBMC. These data indicate that hypericin inhibits mitogen-induced proliferation of malignant T cells from patients with cutaneous T cell lymphoma, PBMC from normal individuals, as well as Epstein-Barr virus-transformed lymphocytes, and that inhibition of cell proliferation is dependent on the concentration of hypericin used and the dose of light required to photoactivate the compound. Induction of apoptosis is, in part, one mechanism by which photoactivated hypericin inhibits malignant T cell proliferation.

Photodynamic therapy with hypericin induces vascular damage and apoptosis in the RIF‐1 mouse tumor model

“…7 The basic mechanism underlying this observed antitumoral activity, however, remains to be determined. Furthermore, in vitro studies from our 10,11 and other groups [12][13][14] have clearly demonstrated that apoptosis is involved in hypericin-mediated cell photo destruction. Whether this mode of cell death contributes to tumor destruction after in vivo PDT with hypericin has never been investigated.…”

ChlamydiapneumoniaeInhibits Apoptosis in Human Peripheral Blood Mononuclear Cells Through Induction of IL-10

“…The therapeutic efficacy of psoralen in combination with UVA has been linked to the potent induction of apoptosis (11). Hypericin, although still in clinical trial, has also been reported to induce a high rate of apoptotic death of normal, transformed, and malignant T lymphocytes and, thus, has promise for the treatment of cutaneous lymphoproliferative and inflammatory disorders (12). Recently, Abrams et al (31) described a C. pneumoniae-associated peptide identified in the blood of Sezary syndrome patients that is able to sustain the growth of malignant Sezary T cells and to prevent apoptotic death.…”

“…The role that cytokines play in infection-mediated antiapoptosis and whether this antiapoptotic effect is unique to C. trachomatis, however, were not addressed. Furthermore, the situation of infected cells treated with other clinically relevant apoptotic inducers such as 8-methoxypsoralen (8-MOP) 3 (11) and hypericin (12), two light-activated photochemotherapeutic reagents that have been used in the treatment of lymphoproliferative diseases and that cause a high level of apoptosis, is also unknown.…”

“…Control plates receiving no exposure to photoactivating wavelengths of light were placed immediately in a 37°C incubator. The remaining plates were exposed to either white light from four fluorescent F15T8CW 15 W bulbs under the tissue culture plates or to UVA light with UVA illumination, as described previously (11,12). Photoactivation with white light lasted for 30 min and delivered the equivalent of 2 J/cm 2 ; UVA light lasted for 4 min and delivered the equivalent of 2 J/cm 2 .…”

Photoactivated hypericin is not genotoxic

“…The procedure involves administration of photosensitizing agent, which is subsequently exposed to a light source of suitable wavelength and can react through free radical mechanisms (Castano et al 2004;Solár et al 2011). HYP can be activated by light in the range of wavelengths between 300-700 nm that includes visible light (400-700 nm) as well as UVA radiation (320-400 nm) (Fox et al 1998;Jendželovská et al 2014). In the presence of oxygen, a series of events leads to a direct tumor death, damage to the microvasculature, and induction of a local inflammatory reaction (Garg et al 2012).…”