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.

Technological Trends Involving Probiotics in the Treatment of Diabetic Neuropathy: A Patent Review (2009-2022)

BACKGROUND

Diabetic neuropathy (DN) causes neuropathic pain, and current treatments are unsatisfactory. Recently studies have demonstrated an assertive correlation between gut microbiota and pain modulation.

OBJECTIVE

Considering the emerging search for new therapies for the control of DN and the growing commercial interest in the probiotics market, this study aimed to provide patents on the use of probiotics in the control of DN.

METHODS

This is a patent prospection performed in the Espacenet Patent database, using the association of keywords and IPC related to probiotics in medical preparations and foods, from 2009 to December 2022.

RESULTS

Results have shown that in 2020, there was a boom in patent filing in the area. Asian countries accounted for more than 50% of all 48 inventions (n = 48), with Japan as the only applicant in 2021. Products being developed in recent years point to effects that may represent an advancement in DN treatment, such as reduced concentration of pro-inflammatory mediators, metabolites and neurotransmitters release, and hypoglycemic potential. All effects were more related to the Lactobacillus and Bifidobacterium genera, associated with more than one property mentioned.

CONCLUSION

The mechanisms attributed to the microorganisms suggest the therapeutic potential of probiotics in the non-pharmacological treatment of pain. New applications for probiotics have resulted from great research interest by academia, but also reflect commercial interests despite the paucity of clinical trials. Thus, the present work supports the evolution of research to explore the benefits of probiotics and their clinical use in DN.

Tonantzitlolone B Modulates the Endogenous Opioid System to Promote Antinociception in Mice

Tonantzitlolone B (TZL-B) is a diterpene isolated from the roots of Stillingia loranthacea. Its antinociceptive effects were investigated in male Swiss mice using the following models of pain: formalin test, inflammation induced by Complete Freund's Adjuvant (CFA), tail flick test, and cold plate test. The influence of TZL-B on the opioid system was assessed in vivo, using opioid antagonists; in silico, investigating the chemical similarity among TZL-B and opioid agonists; and ex vivo, measuring preproenkephalin (PENK) gene expression in the spinal cord by RT-qPCR. TZL-B (10-1000 μg/kg) promoted antinociception in the four experimental models without impairing mice's motor function. TZL-B did not alter paw edema during CFA-induced inflammation. The antinociceptive effects of TZL-B in the tail flick and cold plate tests were diminished by the opioid antagonists naloxone (5 mg/kg), NOR-BNI (0.5 mg/kg), naltrindole (3 mg/kg), and CTOP (1 mg/kg), indicating the involvement of κ-, δ-, and μ-opioid receptors. TZL-B showed no significant chemical similarity to opioid agonists, but the treatment with TZL-B (1000 μg/kg) increased PENK gene expression in the spinal cord of mice. These data suggest that TZL-B promotes antinociception by enhancing the transcription of PENK, hence modulating the endogenous opioid system.

Unveiling Targets for Treating Postoperative Pain: The Role of the TNF-α/p38 MAPK/NF-κB/Nav1.8 and Nav1.9 Pathways in the Mouse Model of Incisional Pain

Although the mouse model of incisional pain is broadly used, the mechanisms underlying plantar incision-induced nociception are not fully understood. This work investigates the role of Na_v1.8 and Na_v1.9 sodium channels in nociceptive sensitization following plantar incision in mice and the signaling pathway modulating these channels. A surgical incision was made in the plantar hind paw of male Swiss mice. Nociceptive thresholds were assessed by von Frey filaments. Gene expression of Na_v1.8, Na_v1.9, TNF-α, and COX-2 was evaluated by Real-Time PCR in dorsal root ganglia (DRG). Knockdown mice for Na_v1.8 and Na_v1.9 were produced by antisense oligodeoxynucleotides intrathecal treatments. Local levels of TNF-α and PGE₂ were immunoenzymatically determined. Incised mice exhibited hypernociception and upregulated expression of Na_v1.8 and Na_v1.9 in DRG. Antisense oligodeoxynucleotides reduced hypernociception and downregulated Na_v1.8 and Na_v1.9. TNF-α and COX-2/PGE₂ were upregulated in DRG and plantar skin. Inhibition of TNF-α and COX-2 reduced hypernociception, but only TNF-α inhibition downregulated Na_v1.8 and Na_v1.9. Antagonizing NF-κB and p38 mitogen-activated protein kinase (MAPK), but not ERK or JNK, reduced both hypernociception and hyperexpression of Na_v1.8 and Na_v1.9. This study proposes the contribution of the TNF-α/p38/NF-κB/Na_v1.8 and Na_v1.9 pathways to the pathophysiology of the mouse model of incisional pain.

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.

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 15^th 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-1β and IL-6. The treatment with EEPA (100 mg/kg) increased the production of the anti-inflammatory cytokine TGF-β. 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.

Pain-like behaviors and local mechanisms involved in the nociception experimentally induced by Latrodectus curacaviensis spider venom

The present study was undertaken to characterize the behavioral manifestations of nociception and the local mechanisms involved with the nociceptive response elicited by Latrodectus curacaviensis venom (LCV) in mice. After the intraplantar LCV inoculation, spontaneous nociception, mechanical and thermal nociceptive thresholds, motor performance, edema and cytokine levels were evaluated using von Frey filaments, hot/cold plate, rota-rod, plethismometer and ELISA, respectively. Analysis of LCV was performed by SDS-PAGE and chromatography. Intraplantar injection of LCV (1-100 ng/paw) induced intense and heat-sensitive spontaneous nociception, mediated by serotonin and bradykinin receptors, TRPV1 channels, as well as by transient local inflammation. LCV (0.1-10 ng/paw) induced mechanical allodynia, which was reduced by the local pretreatment with H1 receptor or TRPV1 antagonists. Corroborating the TRPV1 involvement, in thermal nociception assays, LCV induced a similar response to that of capsaicin, a TRPV1 agonist, facilitating the response to noxious hot stimuli and inhibiting the response to cold noxious stimulation. LCV promoted mast cell degranulation, increased IL-1β paw levels, but did not produce a relevant edematogenic effect. Analysis of LCV components showed a predominance of high molecular weight proteins. This work provides the first mechanistic hypothesis to explain the local pain induced by LCV, the most frequent clinical symptom of human envenomation.