Alejandra Vargas-Caraveo

Physiologically, lipopolysaccharide (LPS) is present in the bloodstream and can be bound to several proteins for its transport (i.e.) LPS binding protein (LBP) and plasma lipoproteins). LPS receptors CD14 and TLR-4 are constitutively expressed in the Central Nervous System (CNS). To our knowledge, LPS infiltration in CNS has not been clearly demonstrated. A naturalistic experiment with healthy rats was performed to investigate whether LPS is present with its receptors in brain. Immunofluorescences showed that lipid A and core LPS were present in circumventricular organs, choroid plexus, meningeal cells, astrocytes, tanycytes and endothelial cells. Co-localization of LPS regions with CD14/TLR-4 was found. The role of lipoprotein receptors (SR-BI, ApoER2 and LDLr) in the brain as targets for a LPS transport mechanism by plasma apolipoproteins (i.e. ApoAI) was studied. Co-localization of LPS regions with these lipoproteins markers was observed. Our results suggest that LPS infiltrates in the brain in physiological conditions, possibly, through a lipoprotein transport mechanism, and it is bound to its receptors in blood-brain interfaces.

The Mexican black-tailed rattlesnake Crotalus molossus nigrescens is distributed in the Mexican plateau. Its venom is known to cause hemolysis and presents fibrinogen coagulase, collagenase and fibrinolytic activities. These activities may be associated with hemostatic alterations, such as platelet aggregation, hemolysis and fibrinolysis, often described in ophidic accidents. However, the mechanisms of action of the C. m. nigrescens venom remain unclear. In this study we investigated the in vitro hemotoxic, neurotoxic, and vasculotoxic effects of the venom. We found that this venom produces two types of hemolytic responses, Oxyhemoglobin release and Methemoglobin formation. As a result of the cytotoxicity to endothelial cells produces morphological biphasic toxicity. The first step in this process is characterized by morphological changes, as well as the loss of cellular adhesion and reduction in thickness. The second phase is characterized by massive cellular aggregation and death. It also induced laminin, type IV collagen, perlecan and nidogen degradation. However, the venom did not modulate the muscular fetal and neuronal nicotinic acetylcholine receptors activity. Thus, we concluded that the C. m. nigrescens venom produced hemolysis and hemorrhages via degradation of the basement membrane components and endothelial cell cytotoxicity, but not by neurotoxicity at the receptor level in nicotinic acetylcholine receptors.

Background: Chronic psychological distress can cause neuroinflammation, but the involvement of leukocytes in this inflammatory response remains unclear. The area postrema (AP) is considered a neural-immune interface because it lacks a blood-brain barrier and a site for leukocyte recruitment in neuroinflammatory conditions induced by immunological insults, but its role in chronic psychological distress has not been explored. Objective: To determine leukocyte recruitment to the AP after chronic psychological distress. Methods: Rats were exposed to cat odor for 5 consecutive days to induce distress, and, on the 6th day, their brains were dissected to perform immunohistofluorescence studies of the AP. Immune cells were identified and quantified with CD45 and CD11b markers. The distribution of neurons and immune cells was determined using TrkA and CD45 markers, respectively. Results: Distress induced a significant increase in CD45+ and CD11b+ cells in the AP. Three immunophenotypes were determined in the control and distress groups: CD45+/CD11b-, CD45+/CD11b+ and CD45-/CD11b+. CD expression, morphology and fluorescence intensity enabled the identification of different immune cell types: starting from longitudinal ramified microglia (mainly in the control group) to amoeboid microglia, monocytes and lymphocytes (mostly in the distressed group). TrkA and CD45 expression in the AP revealed the proximity between soma neurons and leukocytes. Interestingly, some CD45+ cells expressed TrkA, with increased expression in the distressed group. Conclusions: The identification of microglial activation, leukocyte recruitment and the close proximity between neurons and leukocytes in the AP after chronic psychological distress exposure suggests the AP as a site for distress-induced immune responses and engraftment of leukocytes infiltrating the CNS.

The Northern black-tailed rattlesnake (Crotalus molossus molossus) venom is mainly hemotoxic, hemorrhagic, and neurotoxic. Its effects in the central nervous system are unknown and only poorly described for all Viperidae species in general. This is why we are interested in describe the damage induced by C. m. molossus venom in rat brain, particularly in the area postrema capillaries. Four C. m. molossus venom doses were tested (0.02, 0.05, 0.10 and 0.20mg/kg) injected intramuscularly at the lower limb, incubated by 24 hours and the brains were harvested. Area postrema coronal sections were stained with Haematoxylin and Eosin, and examined to observe the venom effect in quantity of capillaries and porphology. Starting from the 0.10mg/kg treatment we observed lysed extravasated erythrocytes and also capillary breakdown, as a consequence of hemorrhages appearance. The number of capillaries decreased significantly in response to the venom dose increment. Hemorrhages could be caused by the metalloproteinase activity on the basal membrane and the apoptosis generated by L-amino acid oxidases. Hemolysis could be caused by phospholipase A2 hemotoxic effect. We conclude that C. m. molossus crude venom produces hemolysis, capillary breakdown, hemorrhages, and the reduction in number of capillaries in the area postrema.