neuropeptide-y and Liver-Cirrhosis

Acute or chronic insults to the liver are usually followed by a tissue repairing process. Unfortunately, this action, in most cases, is not effective enough to restore the normal hepatic structure and function. Instead, fibrogenesis and regenerative nodules formation ensue, which are relatively nonfunctioning. The common final stage of the process is liver cirrhosis with increased intrahepatic resistance to portal venous blood flow. Throughout the entire course, the extrahepatic circulatory dysfunction, including increased splanchnic blood flow, elevated portal venous blood flow and pressure, decreased splanchnic and peripheral vascular resistance, tachycardia, and increased cardiac output, are noted and denoted as portal hypertension with hyperdynamic circulatory dysfunction. When such a condition is established, patients may suffer from fatal complications such as gastroesophageal variceal hemorrhage, hepatic encephalopathy, or hepatorenal syndrome. The cause of such a circulatory dysfunction is not fully elucidated. Nevertheless, clarification of the pathophysiology definitely contributes to the control of portal hypertension-related complications. Herein, the molecular mechanism of this intriguing disaster is reviewed and discussed.

Topics: Animals; Endocannabinoids; Endothelin-1; Humans; Hypertension, Portal; Liver Cirrhosis; Neuropeptide Y; Portal Vein; Splanchnic Circulation; Tumor Necrosis Factor-alpha; Vascular Endothelial Growth Factor A; Vascular Remodeling

Vascular dysfunction in the splanchnic circulation during portal hypertension is characterized by enhanced NO-mediated vasorelaxation and vascular hyporeactivity to norepinephrine that lead to arterial vasodilation. NPY most likely counteracts both of these key features. Firstly, NPY appears to inhibit Ach- and PNS-induced vasorelaxation in mesenteric arteries. This effect is more pronounced in portal hypertensive rats as compared to control, and most likely reflects the inhibition of increased e- and nNOS-derived NO-synthesis during portal hypertensive conditions. Secondly, NPY sensitizes the mesenteric vasculature to alpha(1)-adrenergic vasoconstriction. Most importantly, in portal hypertensive rats but not in sham rats NPY markedly augments vascular contractility and thereby corrects vascular hyporeactivity. Both actions of NPY increase vascular tone and may well act synergistically in the splanchnic circulation during portal hypertension. Moreover, the vasoconstrictive effects of NPY are most pronounced at particularly high levels of alpha(1)-adrenergic activity. Therefore, it appears that NPY becomes increasingly important for optimizing adrenergic vasoconstriction at particularly high adrenergic drive and also for playing a predominant role for vascular homeostasis. Cirrhotic patients present with elevated circulating plasma levels of NPY, which appears to be independent from the severity of liver dysfunction and to correlate with portal pressure. This finding indicates enhanced NPY release during portal hypertension that may represent a compensatory mechanism aimed at counterbalancing arterial vasodilation by restoring the efficacy of endogenous catecholamines and inhibiting vasodilative drive in the splanchnic circulation.

Topics: Humans; Hypertension, Portal; Liver Cirrhosis; Neuropeptide Y; Splanchnic Circulation

This chapter reviews recent evidence that the sympathetic nervous system (SNS) regulates liver repair by modulating the phenotypes of hepatic stellate cells (HSCs), the liver's principal fibrogenic cells, and hepatic epithelial progenitors, i.e., oval cells. SNS nerve fibers touch HSCs and these cells express adrenoceptors, suggesting that HSCs may be targets for SNS neurotransmitters. HSCs also contain catecholamine biosynthetic enzymes, release norepinephrine (NE), and are growth-inhibited by adrenoceptor antagonists. In addition, HSCs from mice with reduced levels of NE grow poorly in culture and exhibit inhibited activation during liver injury. Finally, growth and injury-related fibrogenic responses are rescued by adrenoceptor agonists. Thus, certain SNS inhibitors (SNSIs) protect experimental animals from cirrhosis. Conversely, SNSIs enhance the hepatic accumulation of oval cells (OCs) in injured livers. This response is associated with improved liver injury. Because SNSIs do not affect the expression of cytokines, growth factors, or growth factor receptors that are known to regulate OCs, and OCs express adrenoceptors, it is conceivable that catecholamines influence OCs by direct interaction with OC adrenoceptors. Given evidence that the SNS regulates the viability and activation of HSCs and OCs differentially, SNSIs may be novel therapies to improve the repair of damaged livers.

Topics: Acetylcholine; Animals; Epithelial Cells; Humans; Leptin; Liver; Liver Cirrhosis; Mice; Neuropeptide Y; Neurotransmitter Uptake Inhibitors; Norepinephrine; Sympathetic Nervous System

To explore the effect of negative emotions on serum levels of adrenocorticotropic hormone (ACTH) and neuropeptide Y (NYP) in hepatitis B liver cirrhosis (HBLC) patients.. Totally 617 HBLC patients were assigned to the negative emotion group (415 cases) and the non-negative emotion group (202 cases) judged by negative emotions. Case numbers of various grading Child-Pugh were recorded in the two groups. Their liver functions were compared between the two groups. Serum levels of ACTH and NPY were detected using double antibody sandwich enzyme-linked immunosorbent assay (ELISA) in the two groups.. There was no statistical difference in Child-Pugh grading between the two groups (χ2 = 0.65, P = 0.72). Compared with the non-negative emotional group, serum ACTH levels decreased significantly in the negative emotion group with statistical difference (P < 0.05). There was no statistical difference in serum ACTH levels between the two groups (P > 0.05).. The negative emotion of HBLC patients was not related to the serum ACTH level, but to relatively lower-concentration serum NPY levels.

Topics: Adrenocorticotropic Hormone; Emotions; Hepatitis B; Humans; Liver Cirrhosis; Neuropeptide Y; Serum

Development of liver fibrosis is paralleled by contraction of hepatic stellate cells (HSCs), the main profibrotic hepatic cells. Yet, little is known about the interplay of neprilysin (NEP) and its substrate neuropeptide Y (NPY), a potent enhancer of contraction, in liver fibrosis. We demonstrate that HSCs are the source of NEP. Importantly, NPY originates majorly from the splanchnic region and is cleaved by NEP in order to terminate contraction. Interestingly, NEP deficiency (Nep

Topics: Angiotensin Receptor Antagonists; Angiotensin-Converting Enzyme Inhibitors; Animals; Fibrosis; Humans; Hypertension, Portal; Liver Cirrhosis; Mice; Neprilysin; Neuropeptide Y; Receptors, Neuropeptide Y

Fibroblast activation protein (FAP) is a dipeptidyl peptidase (DPP) and endopeptidase that is weakly expressed in normal adult human tissues but is greatly up-regulated in activated mesenchymal cells of tumors and chronically injured tissue. The identities and locations of target substrates of FAP are poorly defined, in contrast to the related protease DPP4. This study is the first to characterize the physiological substrate repertoire of the DPP activity of endogenous FAP present in plasma. Four substrates, neuropeptide Y (NPY), peptide YY, B-type natriuretic peptide and substance P, were analyzed by mass spectrometry following proteolysis in human or mouse plasma, and by in vivo localization in human liver tissues with cirrhosis and hepatocellular carcinoma (HCC). NPY was the most efficiently cleaved substrate of both human and mouse FAP, whereas all four peptides were efficiently cleaved by endogenous DPP4, indicating that the in vivo degradomes of FAP and DPP4 differ. All detectable DPP-specific proteolysis and C-terminal processing of these neuropeptides was attributable to FAP and DPP4, and plasma kallikrein, respectively, highlighting their combined physiological significance in the regulation of these neuropeptides. In cirrhotic liver and HCC, NPY and its receptor Y2R, but not Y5R, were increased in hepatocytes near the parenchymal-stromal interface where there is an opportunity to interact with FAP expressed on nearby activated mesenchymal cells in the stroma. These novel findings provide insights into the substrate specificity of FAP, which differs greatly from DPP4, and reveal a potential function for FAP in neuropeptide regulation within liver and cancer biology.

Topics: Animals; Carcinoma, Hepatocellular; Case-Control Studies; Dipeptidyl Peptidase 4; Endopeptidases; Gelatinases; Humans; Kinetics; Liver; Liver Cirrhosis; Liver Neoplasms; Membrane Proteins; Mice, Inbred C57BL; Mice, Knockout; Neuropeptide Y; Protease Inhibitors; Proteolysis; Receptors, Neuropeptide Y; Serine Endopeptidases; Species Specificity; Substrate Specificity

Sympathetic nervous system (SNS) signalling regulates murine hepatic fibrogenesis through effects on hepatic stellate cells (HSC), and obesity-related hypertension with SNS activation accelerates progression of non-alcoholic fatty liver disease (NAFLD), the commonest cause of chronic liver disease. NAFLD may lead to cirrhosis. The effects of the SNS neurotransmitters norepinephrine (NE), epinephrine (EPI) and neuropeptide Y (NPY) on human primary HSC (hHSC) function and in NAFLD pathogenesis are poorly understood.. to determine the mechanistic effects of NE/EPI/NPY on phenotypic changes in cultured hHSC, and to study SNS signalling in human NAFLD livers.. Freshly isolated hHSC were assessed for expression of cathecholamine/neuropeptide Y receptors and for the synthesis of NE/EPI. The effects of NE/EPI/NPY and adrenoceptor antagonists prazosin (PRZ)/propranolol (PRL) on hHSC fibrogenic functions and the involved kinases and interleukin pathways were examined. Human livers with proven NAFLD were then assessed for upregulation of SNS signalling components.. Activated hHSC express functional α/β-adrenoceptors and NPY receptors, which are upregulated in the livers of patients with cirrhotic NAFLD. hHSC in culture synthesize and release NE/EPI, required for their optimal basal growth and survival. Exogenous NE/EPI and NPY dose-dependently induced hHSC proliferation, mediated via p38 MAP, PI3K and MEK signalling. NE and EPI but not NPY increased expression of collagen-1α2 via TGF-β without involvement of the pro-fibrogenic cytokines leptin, IL-4 and IL-13 or the anti-fibrotic cytokine IL-10.. hHSC synthesize and require cathecholamines for optimal survival and fibrogenic functionality. Activated hHSC express directly fibrogenic α/β-adrenoceptors and NPY receptors, upregulated in human cirrhotic NAFLD. Adrenoceptor and NPY antagonists may be novel anti-fibrotic agents in human NAFLD.

Topics: Base Sequence; Catecholamines; Cells, Cultured; Chromatography, High Pressure Liquid; Collagen; DNA Primers; Fatty Liver; Hepatic Stellate Cells; Humans; Interleukins; Liver Cirrhosis; Neuropeptide Y; Non-alcoholic Fatty Liver Disease; Norepinephrine; Receptors, Adrenergic; Reverse Transcriptase Polymerase Chain Reaction; Sympathetic Nervous System; Transforming Growth Factor beta; Up-Regulation

Splanchnic vasodilation is an essential disturbance in portal hypertension. Increased systemic sympathetic nerve activity is well known, but potential corresponding vascular desensitization is incompletely characterized. Release of splanchnic sympathetic neurotransmitters noradrenaline (NA) and co-transmitter neuropeptide Y (NPY) remains to be elucidated. Finally, the effects of exogenous NPY on these mechanisms are unexplored.. Portal vein ligated cirrhotic, and control rats were used for in vitro perfusion of mesenteric arteries. Depletion of vascular pressure response was induced by repetitive electric sympathetic perivascular nerve stimulation (PNS) and performed in the absence and presence of exogenous NPY. Additionally, PNS-induced release of NA and NPY was measured.. Mesenteric PNS-induced pressure response was lower in portal hypertension. Depletion of the pressure response to PNS, representing the degree of desensitization, was enhanced in portal hypertension. NA release was elevated, whereas NPY release was attenuated in cirrhosis. Administration of exogenous NPY led to marked recovery from desensitization and vasoconstrictive improvement in cirrhotic rats, being associated with more pronounced decrease of NA release.. Pronounced depletion of splanchnic arterial pressure-response to repetitive sympathetic nerve stimulation in cirrhosis is partly attributable to altered NA release as well as to deficient NPY release. External NPY restores vascular contractility and attenuates pathologically elevated NA release in the portal hypertensive mesenteric vasculature, revealing post-, and prejunctional effects at the vascular smooth muscle motor endplate; therefore outlining encouraging therapeutic strategies.

Topics: Animals; Carbon Tetrachloride; Disease Models, Animal; Electric Stimulation; Hypertension, Portal; Liver Cirrhosis; Male; Mesenteric Arteries; Neuropeptide Y; Neurotransmitter Agents; Norepinephrine; Rats; Rats, Inbred Strains; Sympathetic Nervous System

The hypothalamic-autonomic nervous system (HANS) axis and the hypothalamic-pituitary-adrenal (HPA) axis are stimulated in parallel in response to stress factors under healthy conditions. This physiological synergism of the axes aims at optimizing anti-inflammatory actions. Therefore, we investigated whether this synergism is altered in patients with liver cirrhosis.. As a typical marker of the HANS axis neuropeptide Y (NPY is a neurotransmitter of the sympathetic nerve terminal) and of the HPA axis, cortisol together with adrenocorticotropic hormone (ACTH) and cortisol-binding globulin (CBG), were measured in samples from control subjects and patients with liver cirrhosis.. Plasma NPY was found to be increased in cirrhotic patients compared to control subjects (P < 0.01). This increase was observed to be independent of the severity of liver disease (Child class). Serum cortisol was decreased in cirrhotics, particularly in patients with Child A cirrhosis. Plasma NPY was positively correlated with serum cortisol in control subjects (r = 0.32, P < 0.05) reflecting the parallel activation of both axes under the normal condition. However, serum cortisol was not correlated with plasma NPY in cirrhotic patients. For the subgroup of Child A patients, even a negative correlation between NPY and cortisol was observed (r = -0.43, P < 0.05). No significant change in serum levels of ACTH and its positive correlation with serum cortisol was observed in cirrhotic patients.. The present study demonstrates that the two stress axes seem to act in parallel fashion in control subjects but are uncoupled in liver cirrhosis. We discuss how uncoupling of the two anti-inflammatory axes can occur and may contribute to the increased susceptibility for infections and lethal complications in cirrhotic patients.

Topics: Adrenocorticotropic Hormone; Adult; Aged; Biomarkers; Carrier Proteins; Case-Control Studies; Female; Humans; Hydrocortisone; Hypothalamo-Hypophyseal System; Liver Cirrhosis; Male; Middle Aged; Neuropeptide Y; Pituitary-Adrenal System; Severity of Illness Index; Sympathetic Nervous System

To observe changes of plasma neuropeptide Y(NPY) level in ascitic patients with decompensated cirrhosis pre- and post-treatment, there fore to understand the correlation of NPY with liver function and ascitic formation.. NPY plasma levels in 20 patients with decompensated cirrhosis and ascites were detected by radioimmunological assay.. Plasma NPY levels in patients with cirrhotic ascites were significantly lower than those in normal subjects(P < 0.01) in spite of the increases of NPY after ascites decreased (P < 0.01), which were still lower than those in normal subjects(P < 0.01).. Decreased plasma NPY levels are correlated with the severity of liver damage and may be responsible for the changes of hemodynamics and ascitic formation in patients with liver cirrhosis.

Topics: Adult; Aged; Ascites; Female; Hemodynamics; Humans; Liver Cirrhosis; Male; Middle Aged; Neuropeptide Y

To investigate the relationship between neuropeptide Y (NPY), a potent renal vasoconstrictor peptide released upon marked stimulations of sympathetic nervous system (SNS), and renal and circulatory function in cirrhosis.. Plasma levels of NPY (radioimmunoassay) and norepinephrine and renal function parameters were determined in 17 healthy controls, nine patients with cirrhosis without ascites, and 37 patients with cirrhosis and ascites, of whom 12 had hepatorenal syndrome (HRS).. Patients with ascites showed circulating levels of NPY similar to those of patients without ascites and controls (73+/-4, +/-4 and 68+/-4 pmol/l, respectively; NS). However, patients with HRS had significantly increased levels of NPY with respect to the other groups (110+/-6 pmol/l; P<0.001). NPY levels correlated inversely with renal plasma flow and glomerular filtration rate and directly with norepinephrine. In patients with HRS (n=6) treatment with terlipressin and albumin was associated with a marked improvement in circulatory and renal function and marked suppression of NPY and norepinephrine levels.. Patients with HRS have increased levels of NPY which are related to circulatory dysfunction and SNS activation and may contribute to renal vasoconstriction.

Topics: Ascites; Creatinine; Female; Glomerular Filtration Rate; Hepatorenal Syndrome; Humans; Liver Cirrhosis; Liver Function Tests; Male; Middle Aged; Neuropeptide Y; Norepinephrine; Renal Circulation; Vasoconstriction