Evidences of endocytosis via caveolae following blood-brain barrier breakdown by Phoneutria nigriventer spider venom.

Spider venoms contain neurotoxic peptides aimed at paralyzing prey or for defense against predators; that is why they represent valuable tools for studies in neuroscience field. The present study aimed at identifying the process of internalization that occurs during the increased trafficking of vesicles caused by Phoneutria nigriventer spider venom (PNV)-induced blood-brain barrier (BBB) breakdown. Herein, we found that caveolin-1α is up-regulated in the cerebellar capillaries and Purkinje neurons of PNV-administered P14 (neonate) and 8- to 10-week-old (adult) rats. The white matter and granular layers were regions where caveolin-1α showed major upregulation. The variable age played a role in this effect. Caveolin-1 is the central protein that controls caveolae formation. Caveolar-specialized cholesterol- and sphingolipid-rich membrane sub-domains are involved in endocytosis, transcytosis, mechano-sensing, synapse formation and stabilization, signal transduction, intercellular communication, apoptosis, and various signaling events, including those related to calcium handling. PNV is extremely rich in neurotoxic peptides that affect glutamate handling and interferes with ion channels physiology. We suggest that the PNV-induced BBB opening is associated with a high expression of caveolae frame-forming caveolin-1α, and therefore in the process of internalization and enhanced transcytosis. Caveolin-1α up-regulation in Purkinje neurons could be related to a way of neurons to preserve, restore, and enhance function following PNV-induced excitotoxicity. The findings disclose interesting perspectives for further molecular studies of the interaction between PNV and caveolar specialized membrane domains. It proves PNV to be excellent tool for studies of transcytosis, the most common form of BBB-enhanced permeability.

Temporal relationship between aquaporin-4 and glial fibrillary acidic protein in cerebellum of neonate and adult rats administered a BBB disrupting spider venom.

Two astrocyte markers, the glial water channel aquaporin-4 (AQP4) and the glial fibrillary acidic protein (GFAP), have been implicated in several physiological and pathological conditions in the central nervous system (CNS) as well as in blood-brain barrier breakdown (BBBb). By color segmentation the immunoreactivity of both proteins, we demonstrate that the expression of AQP4 and GFAP was increased in the cerebellum of neonate (14-day-old, P14) and adult (8-week-old) rats administered Phoneutria nigriventer spider venom (PNV) known to cause perivascular edema, BBBb and convulsion. In the cerebellum's gray matter, PNV produced a major response, especially in the granular layer. Parallel increases in AQP4 and GFAP expression occurred 24 h after envenomation in the white matter of P14 and in the molecular layer of adults, as well as in the granular layer 2 h after envenomation. In the Purkinje layer there was a tendency of increased AQP4, for both, neonates (5 h), and adults (2 and 24 h). Moreover, PNV also provoked nonparallel upregulation of both markers with prevalence of upregulation of AQP 4 for P14 rats, and GFAP for adults. The major expression of both proteins was in the gray matter. The data indicates a venom effect in water/electrolyte balance in the cerebellum and the participation of AQP4 in these effects. Age-related and time-related regional differences probably reflect specificity in AQP4 distribution in different astrocytic membrane domains as well as its participation in K(+) buffering and neural activity. This study is the first to associate astrocytic AQP4 expression and reactive gliosis in a model of BBB permeability promoted by P. nigriventer venom. Our data provide compelling evidence that AQP4 expression was increased in the cerebellum of rats administered PNV.

Chromosomes of Theridiidae spiders (Entelegynae): Interspecific karyotype diversity in Argyrodes and diploid number intraspecific variability in Nesticodes rufipes.

Theridiidae is a derived family within the Araneoidea clade. In contrast to closely related groups, the 2n(male) = 20+X(1) X (2) with acro/telocentric chromosomes is the most widespread karyotype among the theridiid spiders. In this work, the cytogenetic analysis of Argyrodes elevatus revealed original chromosome features different from those previously registered for Theridiidae, including the presence of 2n(male) = 20+X with meta/submetacentric chromosomes. Most individuals of Nesticodes rufipes showed family conserved karyotype characteristics. However, one individual had a 2n(male) = 24 due to the presence of an extra chromosome pair, which exhibited regular behavior and reductional segregation during meiosis. After silver staining, mitotic cells exhibited NORs localized on the terminal regions of the short arms of pairs 2, 3, and 4 of A. elevatus and on the terminal regions of long arms of pair 4 of N. rufipes. The comparative analysis with data from phylogenetically related species allowed the clarification of the origin of the interspecific and intraspecific chromosome variability observed in Argyrodes and in N. rufipes, respectively.

Chromosomes of Theridiidae spiders (Entelegynae): interspecific karyotype diversity in Argyrodes and diploid number intraspecific variability in Nesticodes rufipes

Theridiidae is a derived family within the Araneoidea clade. In contrast to closely related groups, the 2n(male) = 20+X1X2 with acro/telocentric chromosomes is the most widespread karyotype among the theridiid spiders. In this work, the cytogenetic analysis of Argyrodes elevatus revealed original chromosome features different from those previously registered for Theridiidae, including the presence of 2n(male) = 20+X with meta/submetacentric chromosomes. Most individuals of Nesticodes rufipes showed family conserved karyotype characteristics. However, one individual had a 2n(male) = 24 due to the presence of an extra chromosome pair, which exhibited regular behavior and reductional segregation during meiosis. After silver staining, mitotic cells exhibited NORs localized on the terminal regions of the short arms of pairs 2, 3, and 4 of A. elevatus and on the terminal regions of long arms of pair 4 of N. rufipes. The comparative analysis with data from phylogenetically related species allowed the clarification of the origin of the interspecific and intraspecific chromosome variability observed in Argyrodes and in N. rufipes, respectively.