Low, but not high, dose triptolide controls neuroinflammation and improves behavioral deficits in toxic model of multiple sclerosis by dampening of NF-κB activation and acceleration of intrinsic myelin repair.

Cuprizone (Cup) is a copper chelating agent frequently used to study factors that affect oligodendrocytes (OLGs) death and acute demyelination. Triptolide (TP), a nuclear factor-kappaB (NF-κB) blocker, is a major bioactive component of Tripterygium wilfordii Hook f. (TWHf) with various therapeutic activities. In this study, we examined the effects of TP on neuroglia activation, inflammation, apoptosis, demyelination, and behavioral deficits in the Cup-induced toxic model of multiple sclerosis (MS). C57BL/6 J mice were fed with chow containing 0.2% Cup for 6 weeks to induce detectable neuroinflammation and myelin loss. TP was administered intraperitoneally at different doses (125, 250 or 500 µg/kg/day) during the last week of the Cup challenge. Although TP substantially decreased Cup-induced NF-κB extra activation, TNF-α and IL-1 over expression, and gliosis in a dose-dependent manner, only low dose of TP (TP-125) was able to raise the number of OLGs precursor cells (NG-2+/O4+), reduce Bax/Bcl-2 ratio and improve behavioral deficits. In addition, TP-125 decreased NF-κB activation on GFAP+ astrocytes more than MAC-3+ microglial and MOG+ oligodendrocytes which suggested the possibility of specific dampening of NF-κB signaling in reactive astrocytes. Behavioral assessments by open-field and rota-rod tests showed that only TP-125 notably improved motor function and motor coordination compared to the Cup group. These findings highlight the pivotal role of NF-κB signaling in the oligodendrogenesis and lesion reduction in demyelination diseases such as MS.

Enhancement of therapeutic DNA vaccine potency by melatonin through inhibiting VEGF expression and induction of antitumor immunity mediated by CD8+ T cells.

To be effective, therapeutic cancer vaccines should stimulate both an effective cell-mediated and a robust cytotoxic CD8+ T-cell response against human papillomavirus (HPV)-infected cells to treat the pre-existing tumors and prevent potential future tumors. In this study, the therapeutic experiments were designed in order to evaluate antitumor effect against the syngeneic TC-1 tumor model. The anti-tumor efficacy of a HPV-16 E7 DNA vaccine adjuvanted with melatonin (MLT) was evaluated in a C57BL/6 mouse tumor model by measuring tumor growth post vaccination and the survival rate of tumor-bearing mice, analyzing the specific lymphocyte proliferation responses in control and vaccinated mice by MTT assay. The E7-specific cytotoxic T cells (CTL) were analyzed by lymphocyte proliferation and lactate dehydrogenates (LDH) release assays. IFN-γ, IL-4 and TNF-α secretion in splenocyte cultures as well as vascular endothelial growth factor (VEGF) and IL-10 in the tumor microenvironment were assayed by ELISA. Our results demonstrated that subcutaneous administration of C57BL/6 mice with a DNA vaccine adjuvanted with MLT dose-dependently and significantly induced strong HPV16 E7-specific CD8+ cytotoxicity and IFN-γ and TNF-α responses capable of reducing HPV-16 E7-expressing tumor volume. A significantly higher level of E7-specific T-cell proliferation was also found in the adjuvanted vaccine group. Furthermore, tumor growth was significantly inhibited when the DNA vaccine was combined with MLT and the survival time of TC-1 tumor bearing mice was also significantly prolonged. In vivo studies further demonstrated that MLT decreased the accumulation of IL-10 and VEGF in the tumor microenvironment of vaccinated mice. These data indicate that melatonin as an adjuvant augmented the cancer vaccine efficiency against HPV-associated tumors in a dose dependent manner.

Melatonin reverses H-89 induced spatial memory deficit: Involvement of oxidative stress and mitochondrial function.

Oxidative stress and mitochondrial dysfunction play indispensable role in memory and learning impairment. Growing evidences have shed light on anti-oxidative role for melatonin in memory deficit. We have previously reported that inhibition of protein kinase A by H-89 can induce memory impairment. Here, we investigated the effect of melatonin on H-89 induced spatial memory deficit and pursued their interactive consequences on oxidative stress and mitochondrial function in Morris Water Maze model. Rats received melatonin (50 and 100µg/kg/side) and H-89(10µM) intra-hippocampally 30min before each day of training. Animals were trained for 4 consecutive days, each containing one block from four trials. Oxidative stress indices, including thiobarbituric acid (TBARS), reactive oxygen species (ROS), thiol groups, and ferric reducing antioxidant power (FRAP) were assessed using spectrophotometer. Mitochondrial function was evaluated through measuring ROS production, mitochondrial membrane potential (MMP), swelling, outer membrane damage, and cytochrome c release. As expected from our previous report, H-89 remarkably impaired memory by increasing the escape latency and traveled distance. Intriguingly, H-89 significantly augmented TBARS and ROS levels, caused mitochondrial ROS production, swelling, outer membrane damage, and cytochrome c release. Moreover, H-89 lowered thiol, FRAP, and MMP values. Intriguingly, melatonin pre-treatment not only effectively hampered H-89-mediated spatial memory deficit at both doses, but also reversed the H-89 effects on mitochondrial and biochemical indices upon higher dose. Collectively, these findings highlight a protective role for melatonin against H-89-induced memory impairment and indicate that melatonin may play a therapeutic role in the treatment of oxidative- related neurodegenerative disorders.