Calponin phosphorylation in cerebral cortex microvessels mediates sustained vasoconstriction after brain trauma

Yeast Secretes High Amounts of Human Calreticulin without Cellular Stress

The ER chaperone calreticulin (CALR) also has extracellular functions and can exit the mammalian cell in response to various factors, although the mechanism by which this takes place is unknown. The yeast Saccharomyces cerevisiae efficiently secretes human CALR, and the analysis of this process in yeast could help to clarify how it gets out of eukaryotic cells. We have achieved a secretion titer of about 140 mg/L CALR in our S. cerevisiae system. Here, we present a comparative quantitative whole proteome study in CALR-secreting yeast using non-equilibrium pH gradient electrophoresis (NEPHGE)-based two-dimensional gel electrophoresis (2DE) as well as liquid chromatography mass spectrometry in data-independent analysis mode (LC-MSE). A reconstructed carrier ampholyte (CA) composition of NEPHGE-based first-dimension separation for 2DE could be used instead of formerly commercially available gels. Using LC-MSE, we identified 1574 proteins, 20 of which exhibited differential expression. The largest group of differentially expressed proteins were structural ribosomal proteins involved in translation. Interestingly, we did not find any signs of cellular stress which is usually observed in recombinant protein-producing yeast, and we did not identify any secretory pathway proteins that exhibited changes in expression. Taken together, high-level secretion of human recombinant CALR protein in S. cerevisiae does not induce cellular stress and does not burden the cellular secretory machinery. There are only small changes in the cellular proteome of yeast secreting CALR at a high level.

Exposure to Blast Overpressure Impairs Cerebral Microvascular Responses and Alters Vascular and Astrocytic Structure

Exposure to blast overpressure may result in cerebrovascular impairment, including cerebral vasospasm. The mechanisms contributing to this vascular response are unclear. The aim of this study was to evaluate the relationship between blast and functional alterations of the cerebral microcirculation and to investigate potential underlying changes in vascular microstructure. Cerebrovascular responses were assessed in sham- and blast-exposed male rats at multiple time points from 2 h through 28 days after a single 130-kPa (18.9-psi) exposure. Pial microcirculation was assessed through a cranial window created in the parietal bone of anesthetized rats. Pial arteriolar reactivity was evaluated in vivo using hypercapnia, barium chloride, and serotonin. We found that exposure to blast leads to impairment of arteriolar reactivity >24 h after blast exposure, suggesting delayed injury mechanisms that are not simply attributed to direct mechanical deformation. Observed vascular impairment included a reduction in hypercapnia-induced vasodilation, increase in barium-induced constriction, and reversal of the serotonin effect from constriction to dilation. A reduction in vascular smooth muscle contractile proteins consistent with vascular wall proliferation was observed, as well as delayed reduction in nitric oxide synthase and increase in endothelin-1 B receptors, mainly in astrocytes. Collectively, the data show that exposure to blast results in delayed and prolonged alterations in cerebrovascular reactivity that are associated with changes in the microarchitecture of the vessel wall and astrocytes. These changes may contribute to long-term pathologies involving dysfunction of the neurovascular unit, including cerebral vasospasm.

Abnormal Rho-associated kinase activity contributes to the dysfunctional myogenic response of cerebral arteries in type 2 diabetes

The structural and functional integrity of the brain, and therefore, cognition, are critically dependent on the appropriate control of blood flow within the cerebral circulation. Inadequate flow leads to ischemia, whereas excessive flow causes small vessel rupture and (or) blood-brain-barrier disruption. Cerebral blood flow is controlled through the interplay of several physiological mechanisms that regulate the contractile state of vascular smooth muscle cells (VSMCs) within the walls of cerebral resistance arteries and arterioles. The myogenic response of cerebral VSMCs is a key mechanism that is responsible for maintaining constant blood flow during variations in systemic pressure, i.e., flow autoregulation. Inappropriate myogenic control of cerebral blood flow is associated with, and prognostic of, neurological deterioration and poor outcome in patients with several conditions, including type 2 diabetes. Here, we review recent advances in our understanding of the role of inappropriate Rho-associated kinase activity as a cause of impaired myogenic regulation of cerebral arterial diameter in type 2 diabetes.

Smooth muscle signalling pathways in health and disease

Smooth muscle contractile activity is a major regulator of function of the vascular system, respiratory system, gastrointestinal system and the genitourinary systems. Malfunction of contractility in these systems leads to a host of clinical disorders, and yet, we still have major gaps in our understanding of the molecular mechanisms by which contractility of the differentiated smooth muscle cell is regulated. This review will summarize recent advances in the molecular understanding of the regulation of smooth muscle myosin activity via phosphorylation/dephosphorylation of myosin, the regulation of the accessibility of actin to myosin via the actin-binding proteins calponin and caldesmon, and the remodelling of the actin cytoskeleton. Understanding of the molecular 'players' should identify target molecules that could point the way to novel drug discovery programs for the treatment of smooth muscle disorders such as cardiovascular disease, asthma, functional bowel disease and pre-term labour.

Synapse loss regulated by matrix metalloproteinases in traumatic brain injury is associated with hypoxia inducible factor-1alpha expression

The present study assessed the role of matrix metalloproteinase-2 (MMP-2) and -9 in synapse loss after traumatic brain injury (TBI) and the role of hypoxia inducible factor-1alpha (HIF-1alpha), a transcription factor up-regulated during hypoxia, in the regulation of MMP-2 and -9 expression post-TBI. Adult male Sprague-Dawley rats (n=6 per group, 400 g-425 g) were injured using Marmarou's closed-head acceleration impact model and allowed to survive for 1, 4, 24 and 48 h. In another set of experiments, 30 min after TBI, animals were treated with Minocycline (inhibitor of MMPs), or 2-Methoxyestradiol (2ME2, inhibitor of HIF-1alpha) and sacrificed at 4 h after injury. Relative amounts of synaptophysin, a presynaptic vesicular protein, HIF-1alpha, as well as MMP-2 and -9 were assessed by real-time PCR and Western blotting. Activity levels of MMP-2 and -9 were determined by zymography. Synaptophysin expression was significantly (p<0.05) decreased at 1 h through 48 h after TBI. A significant increase in gene and protein expressions of HIF-1alpha, MMP-2 and -9, as well as enzyme activity of MMP-2 and -9 at the same time points was also detected. Inhibition of either MMPs or HIF-1alpha significantly reversed the TBI-induced decrease in synaptophysin. Inhibition of HIF-1alpha reduced expression of MMP-2 and -9. This study showed an early detection of a correlation between synaptic loss and MMP expression after TBI. The data also supports a role for HIF-1alpha in the MMP regulatory cascade in synapse loss after TBI, suggesting potential targets for reducing loss of synaptic terminals.

An analysis of regional microvascular loss and recovery following two grades of fluid percussion trauma: a role for hypoxia-inducible factors in traumatic brain injury

Secondary hypoxic/ischemic injuries, stemming from reductions in cerebral blood flow are important contributing factors in progressive neuronal dysfunction after brain trauma. A greater preclinical understanding of how brain trauma leads to secondary hypoxia/ischemia is necessary in the development of posttraumatic brain injury (TBI) therapeutics. To this end, we examined the density of microvascular coverage in the injured and contralateral cortical hemispheres using two intensities of fluid percussion trauma in rats. A silicone microangiography technique showed a significant loss in microvascular density in 2 atmosphere (atm) (16.9+/-3.8%) and 3 atm (15.7+/-1.3%) injured animals relative to sham animals (29.9+/-2.5%; P<0.01). RECA-1 immunohistochemistry indicated that capillary changes involved a reduction in capillary number and diameter. Reduction in microvascular density was shown to be a diffuse phenomenon occurring up to 4 mm rostral and caudal to the injury epicenter. Recovery of microvasculature occurred by 2 weeks after injury only in the 2 atm injury group. Expression of HIF1alpha and increased vascular endothelial growth factor expression were observed in the ipsilateral hippocampus suggesting sufficiently impaired microcirculation resulting in the expression of hypoxic-response proteins. Collectively, the results indicate diffuse and heterogeneous microvascular alterations as well as endogenous expression of neuroprotective and neovascularization pathways after TBI.

Hypoxia-inducible factor-1alpha signaling in aquaporin upregulation after traumatic brain injury

Previous studies have demonstrated that traumatic brain injury (TBI) causes brain edema via aquaporins (AQPs), the water-transporting proteins. In the present study, we determined the role of hypoxia inducible factor-1alpha (HIF-1alpha), which is a transcription factor in response to physiological hypoxia, in regulating expression of AQP4 and AQP9. Adult male Sprague-Dawley rats (400-425g) received a closed head injury using the Marmarou weight drop model with a 450g weight and survived for 1, 4, 24 and 48h. Some animals were administered 30min after injury with 2-methoxyestradiol (2ME2), a naturally occurring metabolite of estradiol which is known to post-transcriptionally down-regulate HIF-1alpha expression, and sacrificed 4h after injury. Real-time PCR and Western blot were used, respectively, to detect gene and protein expressions of manganese superoxide dismutase (MnSOD, showing hypoxic stress), HIF-1alpha, AQP4, and AQP9. ANOVA analysis demonstrated a significant (p<0.05) increase in gene expression of MnSOD, HIF-1alpha, AQP4, and AQP9, starting at 1h after injury through 48h. Western blot analysis further indicated a significant (p<0.05) increase in protein expression of these molecules at the same time points. Pharmacological inhibition of HIF-1alpha by 2ME2 reduced the up-regulated levels of AQP4 and AQP9 after TBI. The present study suggests that hypoxic conditions determined by MnSOD expression after closed head injury contribute to HIF-1alpha expression. HIF-1alpha, in turn, up-regulates expression of AQP4 and AQP9. These results characterize the pathophysiological mechanisms, and suggest possible therapeutic targets for TBI patients.

Calponin control of cerebrovascular reactivity: therapeutic implications in brain trauma

Calponin (Cp) is an actin-binding protein first characterized in chicken gizzard smooth muscle (SM). This review discusses the role of Cp in mediating SM contraction, the biochemical process by which Cp facilitates SM contraction and the function of Cp in the brain. Recent work on the role of Cp in pathological states with emphasis on traumatic brain injury is also discussed. Based on past and present data, the case is presented for targeting Cp for novel genetic and pharmacological therapies aimed at improving outcome following traumatic brain injury (TBI).

Smooth muscle signalling pathways in health and disease

Smooth muscle contractile activity is a major regulator of function of the vascular system, respiratory system, gastrointestinal system and the genitourinary systems. Malfunction of contractility in these systems leads to a host of clinical disorders, and yet, we still have major gaps in our understanding of the molecular mechanisms by which contractility of the differentiated smooth muscle cell is regulated. This review will summarize recent advances in the molecular understanding of the regulation of smooth muscle myosin activity via phosphorylation/dephosphorylation of myosin, the regulation of the accessibility of actin to myosin via the actin-binding proteins calponin and caldesmon, and the remodelling of the actin cytoskeleton. Understanding of the molecular 'players' should identify target molecules that could point the way to novel drug discovery programs for the treatment of smooth muscle disorders such as cardiovascular disease, asthma, functional bowel disease and pre-term labour.

Behavioral pre-conditioning enhances angiogenesis and cognitive outcome after brain trauma

OBJECTIVES

In this study, we used Marmarou's model of traumatic brain injury (TBI) and sought to determine: (1) the effect of TBI on cognitive outcome measured on a radial arm maze; (2) the effect of behavioral conditioning before TBI, i.e. pre-conditioning, on cognitive outcome; (3) the effect of pre-conditioning on angiogenesis.

METHODS

Cognitive outcome was measured by performance on an eight-arm radial maze. Behavioral conditioning consisted of daily exposure of animals to the radial arm maze. Latency and number of errors were recorded as an index of overall performance and acquisition of the test. Extent of angiogenesis was measured by vascular endothelial growth factor receptor 2 (VEGFR2) immunofluorescence and by determining capillary density.

RESULTS

Our results indicated that trauma alone causes significant cognitive impairments. Pre-conditioning caused a marked improvement in radial arm maze performance following injury. These results coincide with both a significant increase in VEGFR2 expression and increased capillary density within the cortex and hippocampus.

DISCUSSION

TBI causes significant impairments in cognition. These deficits can be ameliorated using a pre-conditioning paradigm. While the precise mechanism has yet to be elucidated, our results indicate that angiogenesis may underlie the cognitive sparing seen in pre-conditioned animals.

Neovascularization following traumatic brain injury: possible evidence for both angiogenesis and vasculogenesis

OBJECTIVE

Our goal was to characterize the angiogenic response following traumatic brain injury (TBI).

METHODS

Western analysis for vascular endothelial growth factor (VEGF) expression, double immunofluorescence labeling of endothelium and vascular endothelial growth factor receptor 2 (VEGFR2), bromodioxyuridine (BrdU) incorporation and measurement of capillary density, were all used to determine the temporal angiogenic response following TBI.

RESULTS

The angiogenic factors, VEGF and VEGFR2, increase following trauma. Capillary density increases and BrdU incorporation confirm the presence of newly formed vessels up to 48 hours post-injury.

DISCUSSION

Our results indicated that following TBI, there is a substantial increase in angiogenesis and based on morphologic characterization of BrdU-positive nuclei within the endothelium, we provide evidence for vasculogenesis following injury.