Farnesol, a component of plant-derived honeybee-collected resins, shows JH-like effects in Apis mellifera workers

Farnesol, a sesquiterpene found in all eukaryotes, precursor of juvenile hormone (JH) in insects, is involved in signalling, communication, and antimicrobial defence. Farnesol is a compound of floral volatiles, suggesting its importance in pollination and foraging behaviour. Farnesol is found in the resin of Baccharis dracunculifolia, from which honeybees elaborate the most worldwide marketable propolis. Bees use propolis to seal cracks in the walls, reinforce the wax combs, and as protection against bacteria and fungi. The introduction within a honeybee hive of a compound with potential hormonal activity can be a challenge to the colony survival, mainly because the transition from within-hive to outside activities of workers is controlled by JH. Here, we tested the hypothesis that exogenous farnesol alters the pacing of developing workers. The first assays showed that low doses of the JH precursor (0.1 and 0.01 µg) accelerate pharate-adult development, with high doses being toxic. The second assay was conducted in adult workers and demonstrated bees that received 0.2 µg farnesol showed more agitated behaviour than the control bees. If farnesol was used by corpora allata (CA) cells as a precursor of JH and this hormone was responsible for the observed behavioural alterations, these glands were expected to be larger after the treatment. Our results on CA measurements after 72 h of treatment showed bees that received farnesol had glands doubled in size compared to the control bees (p < 0.05). Additionally, we expected the expression of JH synthesis, JH degradation, and JH-response genes would be upregulated in the treated bees. Our results showed that indeed, the mean transcript levels of these genes were higher in the treated bees (significant for methyl farnesoate epoxidase and juvenile hormone esterase, p < 0.05). These results suggest farnesol is used in honeybees as a precursor of JH, leading to increasing JH titres, and thus modulating the pacing of workers development. This finding has behavioural and ecological implications, since alterations in the dynamics of the physiological changes associated to aging in young honeybees may significantly impact colony balance in nature.

Spinal HMGB1 participates in the early stages of paclitaxel-induced neuropathic pain via microglial TLR4 and RAGE activation

Introduction

Chemotherapy-induced neuropathic pain (CINP) is one of the main adverse effects of chemotherapy treatment. At the spinal level, CINP modulation involves glial cells that upregulate Toll-like receptor 4 (TLR4) and signaling pathways, which can be activated by pro-inflammatory mediators as the high mobility group box-1 (HMGB1).

Objective

To evaluate the spinal role of HMGB1 in the paclitaxel-induced neuropathic pain via receptor for advanced glycation end products (RAGE) and TLR4 activation expressed in glial cells.

Methods

Male C57BL/6 Wild type and TLR4 deficient mice were used in the paclitaxel-induced neuropathic pain model. The nociceptive threshold was measured using the von Frey filament test. In addition, recombinant HMGB1 was intrathecally (i.t.) injected to confirm its nociceptive potential. To evaluate the spinal participation of RAGE, TLR4, NF-kB, microglia, astrocytes, and MAPK p38 in HMGB1-mediated nociceptive effect during neuropathic pain and recombinant HMGB1-induced nociception, the drugs FPS-ZM1, LPS-RS, PDTC, minocycline, fluorocitrate, and SML0543 were respectively administrated by i.t. rout. Microglia, astrocytes, glial cells, RAGE, and TLR4 protein expression were analyzed by Western blot. ELISA immunoassay was also used to assess HMGB1, IL-1β, and TNF-α spinal levels.

Results

The pharmacological experiments demonstrated that spinal RAGE, TLR4, microglia, astrocytes, as well as MAPK p38 and NF-kB signaling are involved with HMGB1-induced nociception and paclitaxel-induced neuropathic pain. Furthermore, HMGB1 spinal levels were increased during the early stages of neuropathic pain and associated with RAGE, TLR4 and microglial activation. RAGE and TLR4 blockade decreased spinal levels of pro-inflammatory cytokines during neuropathic pain.

Conclusion

Taken together, our findings indicate that HMGB1 may be released during the early stages of paclitaxel-induced neuropathic pain. This molecule activates RAGE and TLR4 receptors in spinal microglia, upregulating pro-inflammatory cytokines that may contribute to neuropathic pain.

Risk of Trypanosoma cruzi transmission in southern Minas Gerais, Brazil - Data from 2014 to 2020

Trypanosoma cruzi, the etiologic agent of Chagas disease, is widely distributed in the Americas and is transmitted through vectorial, transfusional, and oral routes. This study aimed to evaluate the risk of vectorial transmission of Chagas disease in municipalities located in southern Minas Gerais, Brazil, by analyzing triatomine specimens collected from 2014 to 2020. All 1522 hematophagous triatomines were identified as Panstrongylus megistus, and were subjected to parasitological and molecular examinations. From 2014 to 2016, approximately 10% of insects were positive in the microscopic analysis of intestinal content, and 27% were positive as detected by the quantitative polymerase chain reaction (qPCR) of the same sampling. However, in the last investigated years, an increase in infected triatomines was observed in microscopic analysis (22%) and qPCR methods (41%). This corroborates the findings of acute human Chagas disease cases, which have increased in the study area from a maximum of 2 cases in previous years to 20 cases in 2019, and 17 cases in 2020 through June. Additionally, bloodmeal sources of infected triatomines were investigated; human blood was detected in up to 85.7% of the samples. Moreover, canine blood was also detected in triatomine intestinal content in recent years, reaching 91% of analyzed insects in 2018. Data on bloodmeal sources have demonstrated human-vector contact and have suggested the participation of dogs in the parasite transmission cycle. These results indicate the risk of T. cruzi vectorial transmission in Southern Minas Gerais and São Paulo owing to the boundary between these states. Thus, enhanced surveillance and vector control of Chagas disease are highly recommended in these areas.

Photobiomodulation enhances the Th1 immune response of human monocytes

This study aims to evaluate the effects of photobiomodulation (PBM) on human monocytes, assessing the oxidative burst and ultimate fungicidal potential of these cells, as well as the gene expression at the mRNA level of CD68, CD80, CD163, CD204, IL-6, TNF-α and IL-10 in derived macrophages. Primary cultures of human monocytes were irradiated with an InGaAlP (660 nm)/GaAlAs (780 nm) diode laser (parameters: 40 mW, 0.04 cm², 1 W/cm²; doses: 200, 400 and 600 J/cm²). Cells were submitted to the chemiluminescence assay, and a microbicidal activity assay against Candida albicans was performed. Reactive oxygen species (ROS) and nitric oxide (NO) production were measured, and cell viability was assessed by the exclusion method using 0.2% Trypan blue reagent. Irradiated monocytes were cultured for 72 h towards differentiation into macrophages. Total RNA was extracted, submitted to reverse transcription and real-time PCR. The results were analysed by ANOVA and the Tukey test (α = 0.05). Irradiated monocytes revealed a significant increase in their intracellular and extracellular ROS (P < 0.001). The 660 nm wavelength and 400 J/cm² dose were the most relevant parameters (P < 0.001). The fungicidal capacity of the monocytes was shown to be greatly increased after PBM (P < 0.001). PBM increased the expression of TNF-α (P = 0.0302) and the production of NO (P < 0.05) and did not impair monocyte viability. PBM induces a pro-inflammatory Th1-driven response in monocytes and macrophages.