Astrocytes spatially restrict VEGF signaling by polarized secretion and incorporation of VEGF into the actively assembling extracellular matrix

The spatial organization of vascular endothelial growth factor (VEGF) signaling is a key determinant of vascular patterning during development and tissue repair. How VEGF signaling becomes spatially restricted and the role of VEGF secreting astrocytes in this process remains poorly understood. Using a VEGF‐GFP fusion protein and confocal time‐lapse microscopy, we observed the intracellular routing, secretion and immobilization of VEGF in scratch‐activated living astrocytes. We found VEGF to be directly transported to cell‐extracellular matrix attachments where it is incorporated into fibronectin fibrils. VEGF accumulated at β1 integrin containing fibrillar adhesions and was translocated along the cell surface prior to internalization and degradation. We also found that only the astrocyte‐derived, matrix‐bound, and not soluble VEGF decreases β1 integrin turnover in fibrillar adhesions. We suggest that polarized VEGF release and ECM remodeling by VEGF secreting cells is key to control the local concentration and signaling of VEGF. Our findings highlight the importance of astrocytes in directing VEGF functions and identify these mechanisms as promising target for angiogenic approaches. GLIA 2016;64:440–456     

Capnocytophaga species: increased resistance of clinical isolates to serum bactericidal action

Capnocytophaga, a newly recognized genus of capnophilic gram-negative bacilli, is part of the normal oral flora. The capacity of Capnocytophaga to cause sepsis and local infections in both immunocompromised and nonimmunocompromised hosts has been documented. Given the recognition that serum resistance may contribute to the virulence of some gram-negative bacteria, we attempted to define the serum sensitivity of clinical isolates of Capnocytophaga from blood and other sites of infection. Whereas nine of nine isolates from human subgingival plaque showed greater than 95% loss of viability under standardized assay conditions, nonoral isolates exhibited variable serum sensitivity. Six of six isolates from blood showed considerable serum resistance (mean survival, 59.7% +/- 38.3%; range, 14.4%-113.3%). Comparison of the electrophoretic mobilities of lipopolysaccharides (LPSs) from sensitive and resistant strains revealed reduced LPS heterogeneity and lower apparent molecular weight among serum-resistant strains. Thus, serum resistance, possibly influenced by LPS structure, may be an important factor contributing to the pathogenic potential of Capnocytophaga spp.     

One scorpion,two venoms: prevenom of Parabuthus transvaalicus acts as an alternative type of venom with distinct mechanism of action

Scorpion venom is a complex mixture of salts, small molecules, peptides, and proteins. Scorpions employ this valuable tool in several sophisticated ways for subduing prey, deterring predators, and possibly during mating. Here, a subtle but clever strategy of venom utilization by scorpions is reported. Scorpions secrete a small quantity of transparent venom when initially stimulated that we propose to name prevenom. If secretion continues, a cloudy and dense venom that is white in color is subsequently released. The prevenom contains a combination of high K(+) salt and several peptides including some that block rectifying K(+) channels and elicit significant pain and toxicity because of a massive local depolarization. The presence of high extracellular K(+) in the prevenom can depolarize cells and also decrease the local electrochemical gradient making it more difficult to reestablish the resting potential. When this positive change to the K(+) equilibrium potential is combined with the blockage of rectifying K(+) channels, this further delays the recovery of the resting potential, causing a prolonged effect. We propose that the prevenom of scorpions is used as a highly efficacious predator deterrent and for immobilizing small prey while conserving metabolically expensive venom until a certain level of stimuli is reached, after which the venom is secreted.     

Ligand-dependent and -independent effects of splice variant 1 of growth hormone-releasing hormone receptor

Existing evidence indicates that, in addition to its neuroendocrine action, growth hormone-releasing hormone (GHRH) acts directly on several nonpituitary tissues, especially neoplasms, and stimulates cell proliferation. We have recently reported that a splice variant of the receptor (SV1) is expressed in various normal tissues and particularly in tumor tissues, producing mitogenic effects on GHRH binding. By using HEC-1A human endometrial carcinoma cells, which express endogenous SV1, we show that, in addition to its ability to mediate the mitogenic effects of GHRH, SV1 also possesses relatively high intrinsic, ligand-independent activity. By using an antisense RNA-based approach we found that SV1 ablation reduces the efficacy of colony formation and the rate of cell proliferation of HEC-1A cells in the absence of exogenous GHRH, and decreases their sensitivity to GHRH when the neurohormone is added to the culture media. This ligand-independent stimulation of cell proliferation appears to be a characteristic property of the truncated form of the receptor, because the expression of SV1 and not of the full-length GHRH receptor stimulated the proliferation of 3T3 fibroblasts in the absence of exogenous GHRH, whereas both forms mediated the proliferative effects of GHRH. Evaluation of 21 specimens of human primary endometrial carcinoma for expression of SV1 by immunohistochemistry indicated that in contrast to the GHRH receptor, which is absent, SV1 is expressed in approximately 43% of the specimens. These findings indicate that SV1 can operate in a ligand-independent as well as a ligand-dependent manner. The overexpression of this form of GHRH receptor may be associated with carcinogenesis.     

Captopril-enhanced renal scintigraphy in the diagnosis of pediatric hypertension

Hypertension in childhood is no longer a rare condition mainly secondary to renal, or renovascular diseases, as a growing proportion of children are obese and hypertensive, with the phenotype of metabolic syndrome. Thus, we need to reconsider our practice in the examination of the hypertensive child and redefine the place of non-invasive methods for screening of renovascular hypertension, and specifically, to evaluate the value of captopril-enhanced renal scintigraphy at the two ends of the palette: the obese child with hypertension and the severely hypertensive prepubertal child. Renal artery stenosis in children is mainly due to fibromuscular dysplasia and stenoses associated with syndromes involving single or multiple smaller branch vessels. This explains the low specificity and sensitivity of the color-Doppler ultrasound method and captopril renal scintigraphy. Even the more sophisticated computed tomography (CT) and magnetic resonance imaging (MRI) angiographic techniques are, at present, not sensitive enough to exclude stenoses of the small branches definitely. Thus, children in whom there is a strong suggestion of renovascular hypertension should undergo angiography with a view to endovascular treatment, as non-invasive imaging has no significant benefit and might lead to a delay in treatment. In the cases when the probability of renovascular disease is moderate a basic assessment of renal function and structure is sufficient. In the neonate, catheter-associated thromboembolic disease is among the most common causes hypertension. It should be controlled medically until the patient is old enough to undergo angiography and angioplasty successfully. Thus, in this age group, there is a place for functional imaging with renal sonography and angiotensin-converting enzyme inhibitor (ACEI) renography to detect hemodynamically significant renovascular disease, with the limitations mentioned above. However, the rapid technical evolution of non-invasive methods requires periodic re-consideration of the actual standpoints.     

Brain mechanisms involved in predatory aggression are activated in a laboratory model of violent intra-specific aggression

Callous-unemotional violence associated with antisocial personality disorder is often called 'predatory' because it involves restricted intention signaling and low emotional/physiological arousal, including decreased glucocorticoid production. This epithet may be a mere metaphor, but may also cover a structural similarity at the level of the hypothalamus where the control of affective and predatory aggression diverges. We investigated this hypothesis in a laboratory model where glucocorticoid production is chronically limited by adrenalectomy with glucocorticoid replacement (ADXr). This procedure was proposed to model important aspects of antisocial violence. Sham and ADXr rats were submitted to resident/intruder conflicts, and the resulting neuronal activation patterns were investigated by c-Fos immunocytochemistry. In line with earlier findings, the share of attacks aimed at vulnerable targets (head, throat and belly) was dramatically increased by ADXr, while intention signaling by offensive threats was restricted. Aggressive encounters activated the mediobasal hypothalamus, a region involved in intra-specific aggression, but sham and ADXr rats did not differ in this respect. In contrast, the activation of the lateral hypothalamus that is tightly involved in predatory aggression was markedly larger in ADXr rats; moreover, c-Fos counts correlated positively with the share of vulnerable attacks and negatively with social signaling. Glucocorticoid deficiency increased c-Fos activation in the central amygdala, a region also involved in predatory aggression. In addition, activation patterns in the periaqueductal gray - involved in autonomic control - also resembled those seen in predatory aggression. These findings suggest that antisocial and predatory aggression are not only similar but are controlled by overlapping neural mechanisms.