The signal transduction pathway causing the synergistic hypertrophic effects of neuropeptide Y and norepinephrine on primary cardiomyocyte

Pathophysiology of oral cancer in experimental animal models: a review with focus on the role of sympathetic nerves

Global increase in incidence and mortality as well as poor prognosis of oral cancer (OC) has intensified efforts towards early detection and prevention of this disfiguring disease. Several studies have been conducted using experimental animal models to understand the pathophysiology and molecular events involved in OC. Lack of identification of specific biomarkers during the multifaceted steps of oral carcinogenesis has hindered its diagnosis and treatment. Solid stress generated by growing tumors as well as abnormalities in tumor vasculature lead to increased interstitial fluid pressure, which could obstruct therapeutic drug delivery to tumors. Furthermore, the sympathetic nervous system is known to affect angiogenesis, vessel permeability, immune responses and carcinogenesis. Recent findings indicate that, in addition to angiogenic and lymphangiogenic factors, tumor cells release neurotrophic factors that initiate innervation. Interactions between cytokines and sympathetic neurotransmitters, and their respective receptors expressed by the nerve, immune and tumor cells appear to influence tumor growth. Thus, understanding the complex signaling processes and interrelationships between vascular, nervous and immune systems during oral carcinogenesis may prove vital for successful prevention and treatment of OC. This review aims at outlining the available knowledge on pathophysiology of OC in experimental animal models including evidence from our own findings.

Neuropeptide Y and neurovascular control in skeletal muscle and skin

Neuropeptide Y (NPY) is a ubiquitous peptide with multiple effects on energy metabolism, reproduction, neurogenesis, and emotion. In addition, NPY is an important sympathetic neurotransmitter involved in neurovascular regulation. Although early studies suggested that the vasoactive effects of NPY were limited to periods of high stress, there is growing evidence for the involvement of NPY on baseline vasomotor tone and sympathetically evoked vasoconstriction in vivo in both skeletal muscle and the cutaneous circulation. In Sprague-Dawley rat skeletal muscle, Y(1)-receptor activation appears to play an important role in the regulation of basal vascular conductance, and this effect is similar in magnitude to the alpha(1)-receptor contribution. Furthermore, under baseline conditions, agonist and receptor-based mechanisms for Y(1)-receptor-dependent control of vascular conductance in skeletal muscle are greater in male than female rats. In skin, there is Y(1)-receptor-mediated vasoconstriction during whole body, but not local, cooling. As with the NPY system in muscle, this neural effect in skin differs between males and females and in addition, declines with aging. Intriguingly, skin vasodilation to local heating also requires NPY and is currently thought to be acting via a nitric oxide pathway. These studies are establishing further interest in the role of NPY as an important vasoactive agent in muscle and skin, adding to the complexity of neurovascular regulation in these tissues. In this review, we focus on the role of NPY on baseline vasomotor tone in skeletal muscle and skin and how NPY modulates vasomotor tone in response to stress, with the aim of compiling what is currently known, while highlighting some of the more pertinent questions yet to be answered.

Glutamate release by neurons evokes a purinergic inhibitory mechanism of osmotic glial cell swelling in the rat retina: activation by neuropeptide Y

Glial cell swelling is a central cause of ischemic edema in the brain and retina; however, the regulation of glial cell volume by endogenous factors in situ is largely unknown. In slices of the postischemic retina of the rat, the somata of glial (Müller) cells swell upon hypotonic stress that is not observed in slices of control retinas. We describe an endogenous signaling pathway that leads to inhibition of the osmotic glial cell swelling, and that is evoked by the release of glutamate from retinal neurons upon application of neuropeptide Y. Glutamate activates metabotropic glutamate receptors on swollen glial cells, which evokes a Ca2+ -independent purinergic signaling cascade that involves release of ATP, P2Y1 receptor activation, and transporter-mediated release of adenosine. Activation of A1 receptors causes the inhibition of osmotic glial cell swelling, by a protein kinase A-dependent activation of K+ and Cl- channels. It is proposed that the glutamate-evoked purinergic receptor signaling of glial cells is crucially involved in the cell volume homeostasis of the retina, and that this mechanism may contribute to the protective effect of adenosine in the ischemic tissue.

Plasma neuropeptide Y immunoreactivity influences left ventricular mass in pheochromocytoma

Left ventricular hypertrophy (LVH) in patients with arterial hypertension is closely related to the levels of blood pressure (BP), catecholamines, angiotensin II and other mitogenic peptides. Pheochromocytoma (pheo) is a type of hypertension caused by excessive production of catecholamines. The aim of this study was to determinate if left ventricular hypertrophy in patients with pheochromocytoma is related to catecholamines and neuropeptide Y (NPY).

METHODS

29 patients with pheochromocytoma (22 F, age 40 +/- 13 years), plasma concentration of neuropeptide Y immunoreactivity, noradrenaline (NA), and adrenaline (A) were determined. Twenty-four hour urine collection for determination of noradrenaline and adrenaline were performed. Every patient had echocardiographic examination and 24 h ambulatory blood pressure monitoring.

RESULTS

Left ventricular hypertrophy was diagnosed in 14 patients. No differences in systolic and diastolic blood pressure in patients with and without left ventricular hypertrophy were found. Plasma noradrenaline and adrenaline levels did not differ between both groups, while plasma neuropeptide Y immunoreactivity was higher in patients with left ventricular hypertrophy than in patients without left ventricular hypertrophy (18.46 +/- 13.26 vs. 9.3 +/- 5.9 fmol/ml (p = 0.02)). Left ventricular mass index (LVMI) correlated with plasma neuropeptide Y-immunoreactivity (r = 0.42 p = 0.023), however, no relationship between left ventricular mass index and plasma or urine noradrenaline and adrenaline levels were found.

CONCLUSION

Our results indicate that mitogenic effect of neuropeptide Y may play a role in pathogenesis of left ventricular hypertrophy in patients with pheochromocytoma.

Obesity and alcoholic liver disease

Obesity potentiates the severity of alcohol-induced liver damage. Ethanol influences adipose tissue production of hormones and cytokines. The mechanisms by which adiposity and ethanol interact to produce hepatic steatosis and steatohepatitis are beginning to be studied. Exacerbation of the proinflammatory state that induces tumor necrosis factor activity and hepatic insulin resistance seems to be involved. However, the precise cellular signals that culminate in hepatocyte dysfunction and death remain controversial. Both hepatocyte apoptosis and necrosis are likely, but further study is needed to develop optimal hepatoprotective strategies. It is currently unclear whether the hepatotoxic consequences of obesity and ethanol ingestion are additive or synergistic. This information has important prognostic implications and might be useful to formulate body mass index-based guidelines for "safe" alcohol consumption. Findings of studies in experimental animals also raise questions about the relation between steatohepatitis and cirrhosis. Despite overwhelming evidence that obesity promotes alcohol-induced steatosis and steatohepatitis, most obese human beings (and mice) who drink alcohol do not become cirrhotic. Moreover, at least in mice, even severe steatohepatitis leads to cirrhosis relatively infrequently. Thus, it is conceivable that, although steatohepatitis is a permissive factor for cirrhosis, it is neither necessary nor sufficient for cirrhosis to occur. The quest to identify the proximal mediators of hepatic fibrosis should probably include an investigation of how various adipokines, neurotransmitters, and cytokines interact to regulate hepatic stellate cells. Armed with such knowledge, further modifying actions of ethanol on these mechanisms can be explored by investigators.

Neuropeptide y: neurotransmitter or trophic factor in the heart?

Neuropeptide Y (NPY) is released from sympathetic neurons and exerts short-term (acute) effects on prejunctional nerve terminals and postjunctional cardiac ion channels. However, NPY also exerts long-term (trophic) effects on angiogenesis, cardiac hypertrophy, autonomic signaling, and cardiac ion channels, including effects on L-type Ca2+ and pacemaker channels.