A. crassicauda, M. eupeus and H. lepturus scorpion venoms initiate a strong in vivo anticancer immune response in CT26-tumor mice model.

In the present in vivo study the anticancer efficacy of the venoms from Androctonus crassicauda, Messobuthus eupeus and Hemiscorpius lepturus scorpions was investigated. In addition, we attempted to clarify whether the immune system is involved in this activity. Initially, the LD50 of the venoms from these scorpions were determined and their 0.1 and 0.2 LD50 were calculated. The toxicity of 0.1 and 0.2 LD50 was tested on healthy mice by daily SC administration of these venoms for 12 consecutive days. CT26 cells were inoculated by SC route in BALB/c mice to establish a sold tumor, and ten days later, the mice were treated with 0.1 and 0.2 LD50 doses of the venoms on daily basis for 12 consecutive days. The tumor volume was measured every 4 days. At day 13, the tumors from untreated-control and venom-treated groups were removed, weighed, and assessed by histopathological and immunohistochemical techniques. In addition, the levels of mRNA expression of IL-12, IFN-γ and IL-1ß were measured by real-time PCR. All the venoms induced anticancer effects as evidenced by significant inhibition in tumor growth; significant increases in inflammatory and CD+-T cells and expression of mRNA IL-12 and IFN-γ in tumor microenvironment of venom-treated as compared to untreated-control. These findings demonstrated, for the first time, that sub-lethal doses of the venoms from these scorpions induce their in vivo anticancer effects by stimulating the immune system. Further studies, specifically designed to identify these active constituents are recommended.

Venlafaxine inhibits naloxone-precipitated morphine withdrawal symptoms: Role of inflammatory cytokines and nitric oxide.

Opioid-induced neuroinflammation plays a role in the development of opioid physical dependence. Moreover, nitric oxide (NO) has been implicated in several oxidative and inflammatory pathologies. Here, we sought to determine whether treatment with venlafaxine during the development of morphine dependence could inhibit naloxone-precipitated withdrawal symptoms. The involvement of neuro-inflammation related cytokines, oxidative stress, and L-arginine (L-arg)-NO pathway in these effects were also investigated. Mice received morphine (50 mg/kg/daily; s.c.), plus venlafaxine (5 and 40 mg/kg, i.p.) once a day for 3 consecutive days. In order to evaluate the possible role of L-arg-NO on the effects caused by venlafaxine, animals received L-arg, L-NAME or aminoguanidine with venlafaxine (40 mg/kg, i.p.) 30 min before each morphine injection for 3 consecutive days. On 4th day of experiment, behavioral signs of morphine-induced physical dependence were evaluated after i.p. naloxone injection. Then, brain levels of tissue necrosis factor-alpha (TNF-α), interleukin-1-beta (IL-1ß), interleukin-6 (IL-6), interleukin-10 (IL-10), brain-derived neurotrophic factor (BDNF), NO and oxidative stress factors including; total thiol, malondialdehyde (MDA) contents and glutathione peroxidase (GPx) activity were determined. Co-administration of venlafaxine (40 mg/kg) with morphine not only inhibited the naloxone-precipitated withdrawal signs including jumping and weight loss, but also reduced the up-regulation of TNF-α, IL-1ß, IL-6, NO and MDA contents in mice brain tissue. However, repeated administration of venlafaxine inhibited the decrease in the brain levels of BDNF, total thiol and GPx. Pre-administration of L-NAME and aminoguanidine improved, while L-arg antagonized the venlafaxine-induced effects. These results provide evidences that venlafaxine could be used as a candidate drug to inhibit morphine withdrawal through the involvement of inflammatory cytokines and l-arginine-NO in mice.

Venlafaxine prevents morphine antinociceptive tolerance: The role of neuroinflammation and the l-arginine-nitric oxide pathway.

Opioid-induced neuroinflammation and the nitric oxide (NO) signal-transduction pathway are involved in the development of opioid analgesic tolerance. The antidepressant venlafaxine (VLF) modulates NO in nervous tissues, and so we investigated its effect on induced tolerance to morphine, neuroinflammation, and oxidative stress in mice. Tolerance to the analgesic effects of morphine were induced by injecting mice with morphine (50 mg/kg) once a day for three consecutive days; the effect of co-administration of VLF (5 or 40 mg/kg) with morphine was similarly tested in a separate group. To determine if the NO precursor l-arginine hydrochloride (l-arg) or NO are involved in the effects rendered by VLF, animals were pre-treated with l-arg (200 mg/kg), or the NO synthesis inhibitors N(ω)-nitro-l-arginine methyl ester (L-NAME; 30 mg/kg) or aminoguanidine hydrochloride (AG; 100 mg/kg), along with VLF (40 mg/kg) for three days before receiving morphine for another three days. Nociception was assessed with a hot-plate test on the fourth day, and the concentration of tumor necrosis factor alpha (TNF-α), interleukin-1beta (IL-1ß), interleukin-6 (IL-6), interleukin-10, brain-derived neurotrophic factor, NO, and oxidative stress factors such as total thiol, malondialdehyde content, and glutathione peroxidase (GPx) activity in the brain was also determined. Co-administration of VLF with morphine attenuated morphine-induced analgesic tolerance and prevented the upregulation of proinflammatory cytokines (TNF-α, IL-1ß, and IL-6), NO, and malondialdehyde in brains of mice with induced morphine tolerance; chronic VLF administration inhibited this decrease in brain-derived neurotrophic factor, total thiol, and GPx levels. Moreover, repeated administration of l-arg before receipt of VLF antagonized the effects induced by VLF, while L-NAME and AG potentiated these effects. VLF attenuates morphine-induced analgesic tolerance, at least partly because of its anti-inflammatory and antioxidative properties. VLF also appears to suppress the development of morphine-induced analgesic tolerance through an l-arg-NO-mediated mechanism.

Venlafaxine Attenuates the Development of Morphine Tolerance and Dependence: Role of L-Arginine/Nitric Oxide/cGMP Pathway.

BACKGROUND: Severe pain reduces quality of life of patients with various diseases, often because chronic morphine therapy results in reduced analgesic effectiveness, or tolerance, leading to escalating doses and distressing adverse effects. Nitric oxide (NO) plays a role in morphine tolerance and dependence. OBJECTIVE: Venlafaxine, an antidepressant, is known to modulate nitric oxide (NO) pathway in nervous tissues. In the present study, the effect of systemic venlafaxine (VLF) on the development of morphine tolerance and dependence, acute morphine-induced antinociception, and the probable involvement of the L-arginine/NO/cGMP pathway in these effects were investigated in mice. METHODS: Animals developed tolerance to the antinociceptive effect of morphine (50 mg/kg, s.c. daily) for 3 consecutive days. NO modulators like L-NAME (NO synthase inhibitor) and L-Arginine (L-Arg, substrate for NO synthase), sildenafil (cGMP-PDE inhibitor) alone or in combination with venlafaxine were used. RESULTS: The results showed that i.p. administration of VLF (5-40 mg/kg) produced antinociceptive effect in a dose-dependent way. Pretreatment with L-Arg (200 mg/kg, i.p.) reversed the antinociception and L-NAME (30 mg/kg, i.p.) and sildenafil (10 mg/kg, i.p.) potentiated the antinociceptive effect. Moreover, co-administration of VLF in non-effective dose (5 mg/kg) with morphine, potentiated acute morphine-induced analgesia (5 mg/kg, s.c.). This effect was antagonized by L-arginine (200 mg/kg, i.p.) and potentiated by L-NAME (30 mg/kg, i.p.) and sildenafil (10 mg/kg, i.p.). On the other hand, VLF was prevented the development of morphine antinociceptive tolerance and dependence. These effects were antagonized by L-arginine (200 mg/kg, i.p.) and potentiated by L-NAME (30 mg/kg, i.p.) and sildenafil (10 mg/kg, i.p.). CONCLUSION: Our data suggest that the combination of VLF with morphine may be a relevant therapeutic implication to manage pain even when tolerance to morphine exists. Moreover, our data demonstrates the involvement of L-Arg/NO/cGMP pathway in the prevention of morphine tolerance and dependence by venlafaxine.