The cerebral endothelium is an active interface between blood and the central nervous system. In addition to being a physical barrier between the blood and the brain, the endothelium also actively regulates metabolic homeostasis, vascular tone and permeability, coagulation, and movement of immune cells. Being part of the blood-brain barrier, endothelial cells of the brain have specialized morphology, physiology, and phenotypes due to their unique microenvironment. Known cardiovascular risk factors facilitate cerebral endothelial dysfunction, leading to impaired vasodilation, an aggravated inflammatory response, as well as increased oxidative stress and vascular proliferation. This culminates in the thrombo-inflammatory response, an underlying cause of ischemic stroke and cerebral small vessel disease (CSVD). These events are further exacerbated when blood flow is returned to the brain after a period of ischemia, a phenomenon termed ischemia-reperfusion injury. Purinergic signaling is an endogenous molecular pathway in which the enzymes CD39 and CD73 catabolize extracellular adenosine triphosphate (eATP) to adenosine. After ischemia and CSVD, eATP is released from dying neurons as a damage molecule, triggering thrombosis and inflammation. In contrast, adenosine is anti-thrombotic, protects against oxidative stress, and suppresses the immune response. Evidently, therapies that promote adenosine generation or boost CD39 activity at the site of endothelial injury have promising benefits in the context of atherothrombotic stroke and can be extended to current CSVD known pathomechanisms. Here, we have reviewed the rationale and benefits of CD39 and CD39 therapies to treat endothelial dysfunction in the brain.
Atherosclerosis impairs endothelium-dependent relaxation of large conduit arteries. Because coronary resistance vessels are spared from the development of overt atherosclerosis, endothelium-dependent responses were examined in these vascular segments. Malaysian cynomolgus monkeys (n = 6) were made atherosclerotic by being fed a 0.7% cholesterol diet for 18 months. Control monkeys (n = 6) were fed a standard diet. Coronary microvessels (122-220 microns) were studied in a pressurized (20 mm Hg), no-flow state using a video-imaging apparatus. Relaxations of microvessels, preconstricted with the thromboxane analogue U46619, were determined in response to acetylcholine, bradykinin, the calcium ionophore A23187, adenosine, and sodium nitroprusside. Microvascular relaxations to bradykinin and A23187 were reduced in atherosclerotic monkeys compared with controls, whereas acetylcholine produced additional contraction in atherosclerotic monkeys. Responses of preconstricted microvessels to adenosine and sodium nitroprusside were identical in atherosclerotic and control animals. Indomethacin did not alter responses in control or atherosclerotic animals. Histologic examination revealed neither intimal thickening nor plaque formation in microvessels of this size class despite marked changes in conduit arteries. Electron microscopy showed minor alterations of endothelial cell morphology in microvessels of atherosclerotic animals. In conclusion, long-term hypercholesterolemia markedly impairs endothelium-dependent vascular relaxation in the coronary microcirculation where overt atherosclerosis does not develop. These changes in endothelial cell function may significantly alter regulation of myocardial perfusion by neurohumoral stimuli.
INTRODUCTION: This study was designed to evaluate the histopathological features of skin microvasculature in patients with a diabetic foot, specifically the number of blood vessels, number of endothelial cells and endothelial thickness.
METHODS: This study involved 41 diabetic foot patients admitted to Hospital Universiti Sains Malaysia for surgical management of foot problems. Skin biopsies were taken for histological evaluation following surgical procedures, such as wound debridement or local foot amputation. The skin microvasculature features examined were the number of blood vessels, the endothelial thickness of the vessels and the cross-sectional endothelial cell count. The findings were compared with the similar parameters of non-diabetic patients (control) and analysed.
RESULTS: The mean blood vessel count (BVC), endothelial cell thickness (ECT) and endothelial cell count (ECC) for the diabetic group were 12.56 +/- 2.77, 4.81 +/- 1.5 micrometres and 7.07 +/- 1.88, respectively. The mean BVC, ECT and ECC for the non-diabetic control group were 5.25 +/- 1.98, 1.9 +/- 0.55 micrometres and 4.11 +/- 1.17, respectively. The mean BVC, ECT and ECC for the diabetic group were significantly higher than those for the non-diabetic control group.
CONCLUSION: The increased number of blood vessels to the skin and their endothelial cell number and thickness may be the contributing factors for problems related to the diabetic foot, such as tendency for skin ulceration, infection and poor wound-healing in these patients. These may also contribute to secondary changes of diabetic foot lesions, indicating failure of adequate vascularisation of the foot.
Acidosis modulates physiologic and pathophysiologic processes but the mechanism of acidotic vasodilatation remains unclear. We therefore explored this in aortic rings from normal and streptozotocin-induced diabetic Sprague-Dawley rats. Phenylephrine (PE)-induced contraction in endothelium-intact and -denuded rings were recorded under normal and acidotic pH with or without drug probes. Acidosis exerted a relaxant effect in endothelium-intact and -denuded euglycaemic and diabetic tissues. l-NAME or methylene blue partially inhibited acidotic relaxation in these endothelium-intact but not the -denuded tissues, with greater inhibition in the diabetic tissues, indicating that acidosis induces relaxation by endothelium-dependent and -independent mechanisms, the former being EDNO-cGMP mediated. Indomethacin had no effect on the tissues, indicating that cyclooxygenase products are neither involved in acidosis-induced vasodilatation nor in the modulation of phenylephrine-contraction. In euglycaemic tissues under normal pH, no K(+) channel blocker altered phenylephrine-contraction, but all (except glibenclamide) enhanced diabetic tissue contraction, indicating that normally, these channels (K(ir), K(V), BK(Ca), K(ATP)) do not modulate phenylephrine-contraction, but they (except K(ATP)) are expressed in diabetes where they attenuate phenylephine-induced contraction and modulate acidosis. Only the K(ir) channel modulates acidotic relaxation in euglycaemic tissues. Only tetraethylammonium and iberiotoxin enhanced phenylephrine-induced contraction in endothelium-denuded diabetic tissues indicating that BK(Ca) attenuates phenylephrine-contraction and that acidotic relaxation in this condition is modulated by a tetraethylammonium-sensitive mechanism. In conclusion, acidosis causes vasodilatation in normal and diabetic tissues via endothelium-dependent and -independent mechanisms differentially modulated by a combination of a NO-cGMP process and K(+) channels, some of which are dormant in the normal state but activated in diabetes mellitus.
Severe dengue can be lethal caused by manifestations such as severe bleeding, fluid accumulation and organ impairment. This study aimed to investigate the role of dengue non-structural 1 (NS1) protein and host factors contributing to severe dengue. Electrical cell-substrate impedance sensing system was used to investigate the changes in barrier function of microvascular endothelial cells treated NS1 protein and serum samples from patients with different disease severity. Cytokines and metabolites profiles were assessed using a multiplex cytokine assay and liquid chromatography mass spectrometry respectively. The findings showed that NS1 was able to induce the loss of barrier function in microvascular endothelium in a dose dependent manner, however, the level of NS1 in serum samples did not correlate with the extent of vascular leakage induced. Further assessment of host factors revealed that cytokines such as CCL2, CCL5, CCL20 and CXCL1, as well as adhesion molecule ICAM-1, that are involved in leukocytes infiltration were expressed higher in dengue patients in comparison to healthy individuals. In addition, metabolomics study revealed the presence of deregulated metabolites involved in the phospholipid metabolism pathway in patients with severe manifestations. In conclusion, disease severity in dengue virus infection did not correlate directly with NS1 level, but instead with host factors that are involved in the regulation of junctional integrity and phospholipid metabolism. However, as the studied population was relatively small in this study, these exploratory findings should be confirmed by expanding the sample size using an independent cohort to further establish the significance of this study.
Endothelial cells have been implicated as key cells in promoting the pathogenesis and spread of cytomegalovirus (CMV) infection. This study describes the isolation and culture of rat brain endothelial cells (RBEC) and further evaluates the infectious potential of a Malaysian rat CMV (RCMV ALL-03) in these cultured cells. Brain tissues were mechanically fragmented, exposed to enzymatic digestion, purified by gradient density centrifugation, and cultured in vitro. Morphological characteristics and expression of von Willebrand factor (factor VIII-related antigen) verified the cells were of endothelial origin. RBEC were found to be permissive to the virus by cytopathic effects with detectable plaques formed within 7 d of infection. This was confirmed by electron microscopy examination which proved the existence of the viral particles in the infected cells. The susceptibility of the virus to these target cells under the experimental conditions described in this report provides a platform for developing a cell-culture-based experimental model for studies of RCMV pathogenesis and allows stimulation of further studies on host cell responses imposed by congenital viral infections.
A total of 96 cases of invasive breast ductal carcinoma were examined for immunohistochemical expression of Bax and Bcl-2 in the epithelial tumor cells and endothelial cells of the blood vessels. We also investigated the association between both proteins in the epithelium in relation to tumor characteristics such as tumor size, grade, lymph node involvement, microvessel density (MVD), hormonal receptors expression and c-erbB-2 overexpression. Bax expression showed a significant association between tumor and endothelial cells (p<0.001) while Bcl-2 expression in tumor cells was inversely associated with that in the endothelial cells (p<0.001). Expression of Bcl-2 in tumor cells was strongly associated with expression of estrogen and progesterone receptors (p=0.003 and p=0.004, respectively). In addition, intratumoral MVD was significantly higher than peritumoral MVD (p<0.001) but not associated with Bax or Bcl-2 expression and other tumor characteristics. We concluded that the number of endothelial cells undergoing apoptosis was in direct linkage with the number of apoptotic tumor cells. Anti-apoptotic activity of the surviving tumor cells appears to propagate cancer progression and this was influenced by the hormonal status of the cells. Tumor angiogenesis was especially promoted in the intratumoral region and angiogenesis was independent of anti-apoptotic activity.
A paramyxovirus virus termed Nipah virus has been identified as the etiologic agent of an outbreak of severe encephalitis in people with close contact exposure to pigs in Malaysia and Singapore. The outbreak was first noted in late September 1998 and by mid-June 1999, more than 265 encephalitis cases, including 105 deaths, had been reported in Malaysia, and 11 cases of encephalitis or respiratory illness with one death had been reported in Singapore. Electron microscopic, serologic, and genetic studies indicate that this virus belongs to the family Paramyxoviridae and is most closely related to the recently discovered Hendra virus. We suggest that these two viruses are representative of a new genus within the family Paramyxoviridae. Like Hendra virus, Nipah virus is unusual among the paramyxoviruses in its ability to infect and cause potentially fatal disease in a number of host species, including humans.