Nicotine increases microvascular blood flow and flow velocity in three groups of brain areas

Nicotine impact on rat substantia nigra compacta

Nicotine neuronal interactions exert an adverse potential in some brain regions and a significant link has been established between tobacco smoke/nicotine and vascular impairment. This work addresses nicotine impact on various components of the substantia nigra compacta (SNc) in rat. Twenty adult male Albino rats were divided equally into two groups: Group I, vehicle-control group (received saline [1 ml/kg body weight intra peritoneally] for 11 days). Group II; nicotine group (received 1.5 mg/kg body weight/day Sc) for 11 days. Nicotine levels were detected in the serum. Specimens were taken from the mid brain, processed and examined using biochemical, immunohistochemical, ultrastructural and morphometric techniques. In nicotine group, biochemical analysis revealed reduction in total antioxidant capacity (TAC), decrease in dopamine and malondialdehyde (MDA) levels. The mean number of light cells, and the mean surface area of nerve cells/field were significantly reduced, with an increase of dark cells were found in nicotine group compared to control. Immunoreactivity in nicotine group revealed an increase in neuronal α-synuclein, reduction in tyrosine hydroxylase enzyme, an increase in caspase 3 and ultrastructure changes suggestive of neuronal apopto. The blood capillaries were markedly affected. Nicotine induced endothelial and pericytic apoptotic changes, irregular lumena and indistinct endothelial junctional complex. Nicotine administered subcutaneously in a small dose may have a deleterious effect on SNc, mainly involving dopaminergic neurons and blood capillaries. This effect seems to be secondary to an oxidative stress that might be produced by reduced TAC and increased MDA levels.

Nicotine pre-exposure reduces stroke-induced glucose transporter-1 activity at the blood-brain barrier in mice

Background

With growing electronic cigarette usage in both the smoking and nonsmoking population, rigorous studies are needed to investigate the effects of nicotine on biological systems to determine long-term health consequences. We have previously shown that nicotine exerts specific neurovascular effects that influence blood brain barrier (BBB) function in response to stroke. In this study, we investigated the effects of nicotine on carrier-mediated glucose transport into ischemic brain. Specifically, the present study investigates glucose transporter-1 (GLUT1) function and expression at the BBB in a focal brain ischemia model of mice pre-exposed to nicotine.

Methods

Nicotine was administrated subcutaneously by osmotic pump at the dose of 4.5 mg/kg/day for 1, 7, or 14 days to reflect the plasma levels seen in smokers. Ischemic-reperfusion (IR) injury was induced by 1 h transient middle cerebral artery occlusion (tMCAO) and 24 h reperfusion. Glucose transport was estimated using an in situ brain perfusion technique with radiolabeled glucose and brain vascular GLUT1 expression was detected with immunofluorescence.

Results

The nicotine pre-exposure (1, 7 & 14 day) resulted in significant reduction in D-glucose influx rate (K_in) across the BBB, with a 49% reduction in 14 day nicotine-infused animals. We observed a 41% increase in carrier-mediated glucose transport across the BBB in saline-infused tMCAO animals compared to saline-infused sham animals. Interestingly, in the tMCAO group of animals pre-exposed to nicotine for 14 days had significantly attenuated increased glucose transport by 80% and 38% compared to saline-infused tMCAO and sham animals respectively. Furthermore, immunofluorescence studies of GLUT1 protein expression in the brain microvascular endothelium confirmed that GLUT1 was also induced in saline-infused tMCAO animals and this protein expression induction was reduced significantly (P < 0.01) with 14 day nicotine pre-exposure in tMCAO animals.

Conclusions

Nicotine pre-exposure reduced the IR-enhanced GLUT1 transporter function and expression at the BBB in a focal brain ischemia mouse model. These studies suggest that nicotine exposure prior to stroke could create an enhanced glucose deprived state at the neurovascular unit (NVU) and could provide an additional vulnerability to enhanced stroke injury.

The quest for a better insight into physiology of fluids and barriers of the brain: the exemplary career of Joseph D. Fenstermacher

In June 2014 Dr. Joseph D. Fenstermacher celebrated his 80th birthday, which was honored by the symposium held in New London, NH, USA. This review discusses Fenstermacher's contribution to the field of fluids and barriers of the CNS. Specifically, his fundamental work on diffusion of molecules within the brain extracellular space and the research on properties of the blood-brain barrier in health and disease are described. Fenstermacher's early research on cerebrospinal fluid dynamics and the regulation of cerebral blood flow is also reviewed, followed by the discussion of his more recent work involving the use of magnetic resonance imaging.

Environmental risk factors for multiple sclerosis: a review with a focus on molecular mechanisms

Multiple sclerosis (MS) is a chronic disabling disease of the central nervous system commonly affecting young adults. Pathologically, there are patches of inflammation (plaques) with demyelination of axons and oligodendrocyte loss. There is a global latitude gradient in MS prevalence, and incidence of MS is increasing (particularly in females). These changes suggest a major role for environmental factors in causation of disease. We have reviewed the evidence and potential mechanisms of action for three exposures: vitamin D, Epstein Barr virus and cigarette smoking. Recent advances supporting gene-environment interactions are reviewed. Further research is needed to establish mechanisms of causality in humans and to explore preventative strategies.

The effect of smoking on the symptoms and progression of multiple sclerosis: a review

Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative disorder of the central nervous system with characteristic demyelinating lesions and axonal loss. MS accounts for the most common cause of neurological disability in young adults in the Western world. The clinical manifestations and the course of MS are highly variable. The early stage of the disease is usually characterized by attacks of neurological dysfunction with complete or incomplete recovery, however, with time disability accumulates in many patients. MS is believed to result from an interplay between susceptibility genes and environmental factors, one of which is smoking. Smoking, a worldwide epidemic, can be regarded as an important risk factor for MS particularly because of its modifiable nature in the quest to prevent or temper the disease course in MS as well as providing possible insights into MS pathogenesis. There are also reports that smoking may influence the symptoms and disease progression in patients with MS. The purpose of this article is to review the effects of smoking on MS symptoms and progression. We conclude that (1) although there are some early reports on worsening of MS symptoms by smoking, the existing evidence is insufficient to thoroughly assess the effects of smoking on the myriad of MS symptoms and (2) smoking seems to adversely influence disease progression in MS patients. We also discuss the potential biological mechanisms linking smoking and MS.

Multimodal measurements of blood plasma and red blood cell volumes during functional brain activation

As an alternative to functional magnetic resonance imaging (fMRI) with blood oxygenation level dependent (BOLD) contrast, cerebral blood volume (CBV)-weighted fMRI with intravascular contrast agents in animal models have become popular. In this study, dynamic measurements of CBV were performed by magnetic resonance imaging (MRI) and laser-Doppler flowmetry (LDF) in alpha-chloralose anesthetized rats during forepaw stimulation. All recordings were localized to the contralateral primary somatosensory cortex as revealed by BOLD at 11.7 T. Ultra-small superparamagnetic iron oxide (15 mg/kg)--a plasma-borne MRI contrast agent with a half-life of several hours in blood circulation--was used to quantify changes in magnetic field inhomogeneity in blood plasma. The LDF backscattered laser light (805 nm), which reflects the amount of red blood cells, was used to measure alterations in the non-plasma compartment. Dynamic and layer-specific comparisons of the two CBV signals during functional hyperemia revealed excellent correlations (>0.86). These results suggest that CBV measurements from either compartment may be used to reflect dynamic changes in total CBV. Furthermore, by assuming steady-state mass balance and negligible counter flow, these results indicate that volume hematocrit is not appreciably affected during functional activation.