Ayahuasca and its major component harmine promote antinociceptive effects in mouse models of acute and chronic pain.

ETHNOPHARMACOLOGICAL RELEVANCE: Ayahuasca (AYA) is a psychedelic brew used in religious ceremonies. It is broadly used as a sacred medicine for treating several ailments, including pain of various origins. AIM OF THE STUDY: To investigate the antinociceptive effects of AYA and its mechanisms in preclinical models of acute and chronic pain in mice, in particular during experimental neuropathy. MATERIALS AND METHODS: The antinociceptive effects of AYA administered orally were assessed in the following models of pain: formalin test, Complete Freund's Adjuvant (CFA)-induced inflammation, tail flick test, and partial sciatic nerve ligation model of neuropathic pain. Antagonism assays and Fos immunohistochemistry in the brain were performed. AYA-induced toxicity was investigated. AYA was chemically characterized. The antinociceptive effect of harmine, the major component present in AYA, was investigated. RESULTS: AYA (24-3000 µL/kg) dose-dependently reduced formalin-induced pain-like behaviors and CFA-induced mechanical allodynia but did not affect CFA-induced paw edema or tail flick latency. During experimental neuropathy, single treatments with AYA (24-3000 µL/kg) reduced mechanical allodynia; daily treatments once or twice a day for 14 days promoted consistent and sustained antinociception. The antinociceptive effect of AYA (600 µL/kg) was reverted by bicuculline (1 mg/kg) and methysergide (5 mg/kg), but not by naloxone (5 mg/kg), phaclofen (2 mg/kg), and rimonabant (10 mg/kg), suggesting the roles of GABAA and serotonergic receptors. AYA increased Fos expression in the ventrolateral periaqueductal gray and nucleus raphe magnus after 1 h, but not after 6 h or 14 days of daily treatments. AYA (600 µL/kg) twice a day for 14 days did not alter mice's motor function, spontaneous locomotion, body weight, food and water intake, hematological, biochemical, and histopathological parameters. Harmine (3.5 mg/kg) promoted consistent antinociception during experimental neuropathy. CONCLUSIONS: AYA promotes consistent antinociceptive effects in different mouse models of pain without inducing detectable toxic effects. Harmine is at least partially accountable for the antinociceptive properties of AYA.

Physalis angulata reduces the progression of chronic experimental periodontitis by immunomodulatory mechanisms.

ETHNOPHARMACOLOGICAL RELEVANCE: Physalis angulata is an herb found in tropical and subtropical regions of the world; it is widely applied in popular medicine due to the therapeutic properties of the whole plant and its parts. Extracts and infusions of this plant have been extensively applied in folk medicine worldwide to treat inflammatory and immune-mediated diseases, including oral inflammatory conditions such as sore throat and gingivitis. AIM OF THE STUDY: The present study was designed to investigate the protective effects of the ethanolic extract of P. angulata (EEPA) in a murine model of chronic periodontitis, aiming to corroborate its traditional use as an anti-inflammatory and immunomodulatory agent, and to point out possible mechanisms involved in these effects. MATERIALS AND METHODS: EEPA was obtained from the stems of P. angulata collected in Belém (PA, Brazil). Chronic periodontitis was induced in male C57BL/6 mice by 12 administrations of lipopolysaccharide (LPS; 20 µg/1µL) into the gingival papilla in the course of 28 days. Starting from the 15th day after the first LPS injection, mice were daily treated with EEPA (50 or 100 mg/kg), nimesulide (25 mg/kg, reference drug), or vehicle by oral route for 14 days. At the end of the experimental period, alveolar bone loss was evaluated along with the gingival expression of biomarkers of periodontitis and cytokines by RT-q-PCR and ELISA. Hematological and biochemical parameters suggestive of systemic toxicity were also evaluated. The transcriptional activity of NF-κB was investigated using the luciferase assay in macrophages. RESULTS: Mice with chronic experimental periodontitis suffered alveolar bone loss that was prevented by the treatment with EEPA (50 or 100 mg/kg) or nimesulide (25 mg/kg). EEPA (50 and 100 mg/kg) and nimesulide (25 mg/kg) reduced mRNA levels of MMP-9 mRNA, but not of TIMP-1 in gingival tissue of periodontitis-induced mice. Both treatments also reduced the production of the pro-inflammatory cytokines IL-1ß and IL-6. The treatment with EEPA (100 mg/kg) increased the production of the anti-inflammatory cytokine TGF-ß. No hematological or biochemical alterations were caused by the daily treatment with EEPA. In vitro luciferase assay suggested that a putative mechanism of EEPA is reducing the transcriptional activity of NF-κB. CONCLUSIONS: EEPA exhibited a disease-modifying effect in the chronic experimental periodontitis, along with unidentifiable systemic toxicity. This work corroborates the traditional use of P. angulata in oral inflammatory conditions and provides mechanistic hypotheses to explain its therapeutic effects.

Effects of photobiomodulation therapy on the local experimental envenoming by Bothrops leucurus snake.

Bothrops leucurus is the major causative agent of snakebites in Brazil's Northeast. The systemic effects of its venom are effectively neutralized by antivenom therapy, preventing bitten patients' death. However, antivenom fails in neutralizing local effects that include intense pain, edema, bleeding, and myonecrosis. Such effects can lead to irreversible sequels, representing a clinically relevant issue for which there is no current effective treatment. Herein, the effects of photobiomodulation therapy (PBMT) were tested in the local actions induced by B. leucurus venom (BLV) in mice (n = 123 animals in 20 experimental groups). A continuous emission AlGaAs semiconductor diode laser was used in two wavelengths (660 or 780 nm). Mechanical nociceptive thresholds were assessed with the electronic von Frey apparatus. Local edema was determined by measuring the increase in paw thickness. Hemorrhage was quantified by digital measurement of the bleeding area. Myotoxicity was evaluated by serum creatine kinase (CK) activity and histopathological analysis. PBMT promoted anti-hypernociception in BLV-injected mice; irradiation with the 660 nm laser resulted in faster effect onset than the 780 nm laser. Both laser protocols reduced paw edema formation, whether irradiation was performed immediately or half an hour after venom injection. BLV-induced hemorrhage was not altered by PBMT. Laser irradiation delayed, but did not prevent myotoxicity caused by BLV, as shown by a late increase in CK activity and histopathological alterations. PBMT was effective in the control of some of the major local effects of BLV refractory to antivenom. It is a potential complementary therapy that could be used in bothropic envenoming, minimizing the morbidity of these snakebite accidents.

Widow spiders in the New World: a review on Latrodectus Walckenaer, 1805 (Theridiidae) and latrodectism in the Americas

Humankind has always been fascinated by venomous animals, as their toxic substances have transformed them into symbols of power and mystery. Over the centuries, researchers have been trying to understand animal venoms, unveiling intricate mixtures of molecules and their biological effects. Among venomous animals, Latrodectus Walckenaer, 1805 (widow spiders) have become feared in many cultures worldwide due to their extremely neurotoxic venom. The Latrodectus genus encompasses 32 species broadly spread around the globe, 14 of which occur in the Americas. Despite the high number of species found in the New World, the knowledge on these spiders is still scarce. This review covers the general knowledge on Latrodectus spp. from the Americas. We address widow spiders' taxonomy; geographical distribution and epidemiology; symptoms and treatments of envenomation (latrodectism); venom collection, experimental studies, proteome and transcriptome; and biotechnological studies on these Latrodectus spp. Moreover, we discuss the main challenges and limitations faced by researchers when trying to comprehend this neglected group of medically important spiders. We expect this review to help overcome the lack of information regarding widow spiders in the New World.(AU)