Pioneering in vitro characterization of macrophage response induced by scorpion venoms from the Brazilian Amazon.

There are several scorpion species of medical relevance around the world. Some of them are well characterized by their toxins and clinical outcomes. Brazilian Amazon has a great amount of these arthropods that have an impact in the scorpionism events specifically in this region of Brazil. Recently, several studies pointed out the immune system activation during scorpion envenouming as an important facet of scorpionism, inducing a sepsis-like state that culminates in clinical severity and death. In this work, we characterized the macrophage response of three species of clinical relevance in Brazilian Amazon: Tityus silvestris, T. metuendus and T. obscurus and one specie with no toxic effects to humans, Brotheas amazonicus. All the four species analyzed were able to induce pro- and anti-inflammatory cytokine production in a J774.1 murine macrophage model. This activation was dependent on TLR2/TLR4/MyD88 activation and abolished by TLRs antagonists. These results suggest that the venoms of the four species analyzed were able to induce macrophage response in agreement to the well-established immune activation by T. serrulatus venom. Our findings provide new insights into the clinical repercussions of scorpionism of uncharacterized species and point to new biotechnological applications of these venoms and possible supportive therapies in scorpionism.

On the noxious black Amazonian scorpion, Tityus obscurus (Scorpiones, Buthidae): Taxonomic notes, biology, medical importance and envenoming treatment.

Tityus obscurus has caused mild, moderate and severe accidents of medical relevance in the eastern Brazilian Amazon and French Guiana. Tityus obscurus has sexual dimorphism although males and females have uniform black coloration. In the Amazon, one of the habitats of this scorpion is seasonally flooded forests (igapós and várzeas). However, most stings occur in terra firme forest areas (non-flooded region), where most rural communities are located. Adults and children stung by T. obscurus may experience an "electric shock" sensation for more than 30 h after the sting. Our data shows that people inhabiting remote forest areas, including rubber tappers, fishermen and indigenous people, with no access to anti-scorpion serum, use parts of native plants, such as seeds and leaves, against pain and vomiting caused by scorpion stings. Although there is a technical effort to produce and distribute antivenoms in the Amazon, many cases of scorpion stings are geographically unpredictable in this region, due to the lack of detailed knowledge of the natural distribution of these animals. In this manuscript, we compile information on the natural history of T. obscurus and the impact of its envenoming on human health. We identify the natural sites that host this scorpion in the Amazon, in order to warn about the risk of human envenoming. The use of specific antivenom serum is the recommended treatment for accidents involving venomous animals. However, atypical symptoms not neutralized by the available commercial antivenom are reported in the Amazon region. Facing this scenario, we present some challenges to the study of venomous animals in the Amazon rainforest and possible experimental bottlenecks and perspectives for establishing a method aimed at producing an efficient antivenom.

On the noxious black amazonian scorpion, Tityus obscurus (Scorpiones, Buthidae): taxonomic notes, biology, medical importance and envenoming treatment

Tityus obscurus has caused mild, moderate and severe accidents of medical relevance in the eastern Brazilian Amazon and French Guiana. Tityus obscurus has sexual dimorphism although males and females have uniform black coloration. In the Amazon, one of the habitats of this scorpion is seasonally flooded forests (igapós and várzeas). However, most stings occur in terra firme forest areas (non-flooded region), where most rural communities are located. Adults and children stung by T. obscurus may experience an “electric shock” sensation for more than 30 h after the sting. Our data shows that people inhabiting remote forest areas, including rubber tappers, fishermen and indigenous people, with no access to anti-scorpion serum, use parts of native plants, such as seeds and leaves, against pain and vomiting caused by scorpion stings. Although there is a technical effort to produce and distribute antivenoms in the Amazon, many cases of scorpion stings are geographically unpredictable in this region, due to the lack of detailed knowledge of the natural distribution of these animals. In this manuscript, we compile information on the natural history of T. obscurus and the impact of its envenoming on human health. We identify the natural sites that host this scorpion in the Amazon, in order to warn about the risk of human envenoming. The use of specific antivenom serum is the recommended treatment for accidents involving venomous animals. However, atypical symptoms not neutralized by the available commercial antivenom are reported in the Amazon region. Facing this scenario, we present some challenges to the study of venomous animals in the Amazon rainforest and possible experimental bottlenecks and perspectives for establishing a method aimed at producing an efficient antivenom.

Meiotic analyses show adaptations to maintenance of fertility in X1Y1X2Y2X3Y3X4Y4X5Y5 system of amazon frog Leptodactylus pentadactylus (Laurenti, 1768).

Heterozygous chromosomal rearrangements can result in failures during the meiotic cycle and the apoptosis of germline, making carrier individuals infertile. The Amazon frog Leptodactylus pentadactylus has a meiotic multivalent, composed of 12 sex chromosomes. The mechanisms by which this multi-chromosome system maintains fertility in males of this species remain undetermined. In this study we investigated the meiotic behavior of this multivalent to understand how synapse, recombination and epigenetic modifications contribute to maintaining fertility and chromosomal sexual determination in this species. Our sample had 2n = 22, with a ring formed by ten chromosomes in meiosis, indicating a new system of sex determination for this species (X1Y1X2Y2X3Y3X4Y4X5Y5). Synapsis occurs in the homologous terminal portion of the chromosomes, while part of the heterologous interstitial regions performed synaptic adjustment. The multivalent center remains asynaptic until the end of pachytene, with interlocks, gaps and rich-chromatin in histone H2A phosphorylation at serine 139 (γH2AX), suggesting transcriptional silence. In late pachytene, paired regions show repair of double strand-breaks (DSBs) with RAD51 homolog 1 (Rad51). These findings suggest that Rad51 persistence creates positive feedback at the pachytene checkpoint, allowing meiosis I to progress normally. Additionally, histone H3 trimethylation at lysine 27 in the pericentromeric heterochromatin of this anuran can suppress recombination in this region, preventing failed chromosomal segregation. Taken together, these results indicate that these meiotic adaptations are required for maintenance of fertility in L. pentadactylus.

Meiosis in the scorpion Tityus silvestris: new insights into achiasmatic chromosomes.

Achiasmatic male meiosis in scorpions is characterized by a high frequency of gaps, asynaptic regions and multivalent associations. Here, we performed an immunocytogenetic analysis to investigate recombination, and synapsis and chromatin-remodeling events during meiosis of the scorpion Tityus silvestris Our results demonstrate that the synaptonemal complex (SC) begins its organization in the zygotene stage and persists until metaphase I. The advancement of the synaptic process is related to the epigenetic modification histone H3 lysine 27 trimethylation (H3K27m3). The distribution and dynamics patterns of variant γH2AX and recombinase Rad51 during achiasmatic meiosis suggests formation and repair of DNA double-strand breaks (DSBs) during early stages of prophase I. The epigenetic modifications, histone H3 lysine 4 trimethylation (H3K4m3) and histone H3 lysine 9 acetylation (H3K9ac), showed a dispersed distribution along the bivalents, suggesting that transcriptional activity is maintained constitutively during prophase I. However, H3K9ac modifications are absent in constitutive heterochromatin carrying the 45S rDNA in pachytene and post-pachytene stages. Collectively, our data demonstrate that T. silvestris exhibits adaptations to the achiasmatic mode, and suggest that epigenetic modifications may act in the regulation of these mechanisms to favor the normal continuation of meiosis in this scorpion.