scholarly journals Cyclic GMP in Liver Cirrhosis—Role in Pathophysiology of Portal Hypertension and Therapeutic Implications

2021 ◽  
Vol 22 (19) ◽  
pp. 10372
Author(s):  
Wolfgang Kreisel ◽  
Adhara Lazaro ◽  
Jonel Trebicka ◽  
Markus Grosse Perdekamp ◽  
Annette Schmitt-Graeff ◽  
...  

The NO-cGMP signal transduction pathway plays a crucial role in tone regulation in hepatic sinusoids and peripheral blood vessels. In a cirrhotic liver, the key enzymes endothelial NO synthase (eNOS), soluble guanylate cyclase (sGC), and phosphodiesterase-5 (PDE-5) are overexpressed, leading to decreased cyclic guanosine-monophosphate (cGMP). This results in constriction of hepatic sinusoids, contributing about 30% of portal pressure. In contrast, in peripheral arteries, dilation prevails with excess cGMP due to low PDE-5. Both effects eventually lead to circulatory dysfunction in progressed liver cirrhosis. The conventional view of portal hypertension (PH) pathophysiology has been described using the “NO-paradox”, referring to reduced NO availability inside the liver and elevated NO production in the peripheral systemic circulation. However, recent data suggest that an altered availability of cGMP could better elucidate the contrasting findings of intrahepatic vasoconstriction and peripheral systemic vasodilation than mere focus on NO availability. Preclinical and clinical data have demonstrated that targeting the NO-cGMP pathway in liver cirrhosis using PDE-5 inhibitors or sGC stimulators/activators decreases intrahepatic resistance through dilation of sinusoids, lowering portal pressure, and increasing portal venous blood flow. These results suggest further clinical applications in liver cirrhosis. Targeting the NO-cGMP system plays a role in possible reversal of liver fibrosis or cirrhosis. PDE-5 inhibitors may have therapeutic potential for hepatic encephalopathy. Serum/plasma levels of cGMP can be used as a non-invasive marker of clinically significant portal hypertension. This manuscript reviews new data about the role of the NO-cGMP signal transduction system in pathophysiology of cirrhotic portal hypertension and provides perspective for further studies.

2020 ◽  
Vol 21 (17) ◽  
pp. 6223 ◽  
Author(s):  
Wolfgang Kreisel ◽  
Denise Schaffner ◽  
Adhara Lazaro ◽  
Jonel Trebicka ◽  
Irmgard Merfort ◽  
...  

Liver cirrhosis is a frequent condition with high impact on patients’ life expectancy and health care systems. Cirrhotic portal hypertension (PH) gradually develops with deteriorating liver function and can lead to life-threatening complications. Other than an increase in intrahepatic flow resistance due to morphological remodeling of the organ, a functional dysregulation of the sinusoids, the smallest functional units of liver vasculature, plays a pivotal role. Vascular tone is primarily regulated by the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway, wherein soluble guanylate cyclase (sGC) and phosphodiesterase-5 (PDE-5) are key enzymes. Recent data showed characteristic alterations in the expression of these regulatory enzymes or metabolite levels in liver cirrhosis. Additionally, a disturbed zonation of the components of this pathway along the sinusoids was detected. This review describes current knowledge of the pathophysiology of PH with focus on the enzymes regulating cGMP availability, i.e., sGC and PDE-5. The results have primarily been obtained in animal models of liver cirrhosis. However, clinical and histochemical data suggest that the new biochemical model we propose can be applied to human liver cirrhosis. The role of PDE-5 as potential target for medical therapy of PH is discussed.


2003 ◽  
Vol 20 (2) ◽  
pp. 165-176 ◽  
Author(s):  
TODD A. BLUTE ◽  
CHRISTIANNE STRANG ◽  
KENT T. KEYSER ◽  
WILLIAM D. ELDRED

Acetylcholine is one of the primary excitatory neurotransmitters/neuromodulators in the retina, but little is known about the downstream signaling pathways it can activate. The present study immunocytochemically examines the potential sources of acetylcholine and the location of the nicotinic cholinergic receptors in the turtle retina. It also examines how activation of these receptors can influence the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signal-transduction pathways. Photoreceptors, amacrine cells, and potentially ganglion cells contain choline acetyltransferase-like immunoreactivity (LI). Nicotinic acetylcholine receptors are immunocytochemically localized on photoreceptors, horizontal, bipolar, and ganglion cells. Nitric oxide imaging indicates that stimulation with nicotine increases NO production primarily in photoreceptors, horizontal, Müller, bipolar, and ganglion cells. In turn, very select populations of amacrine cells respond to this NO with increased levels of cGMP-LI. Selective inhibitors reveal that nitric oxide synthase is involved in most, but not all, of these increases in cGMP-LI. These results show that acetylcholine can activate the NO/cGMP signal-transduction pathways in both the inner and outer retina. This indicates that both of the major excitatory retinal transmitters, glutamate and acetylcholine, can stimulate NO production that increases levels of cGMP-LI in overlapping populations of retinal cells.


1979 ◽  
Vol 23 (3) ◽  
pp. 248-252 ◽  
Author(s):  
F. Burcharth ◽  
T. Alsner ◽  
K. Bertheussen ◽  
T. Rosendal ◽  
S. E. Nielsen

2020 ◽  
Vol 3 (31) ◽  
pp. 53-61
Author(s):  
T. Bentsa ◽  

Introduction. Liver cirrhosis (LC) is an important medical and socio-economic problem not only in Ukraine, but throughout the world. The urgency of this disease is due to its significant spread, increase of the number of etiological factors, as well as the occurrence of severe complications, which often leads to death. The prognosis depends on several factors, such as etiology, the severity of liver damage, the presence of complications and concomitant diseases. The aim of the study. To review the scientific literature and summarize the published studies devoted to the study of the etiology, classification, clinical picture and diagnosis of liver cirrhosis. Materials and methods. The content analysis, the method of systemic and comparative analysis, the bibliosemantic method of studying the current scientific research on the etiology, classification, clinical picture and diagnosis of LC were used. The search for sources was carried out in scientometric databases: PubMed-NCBI, Medline, Research Gate, Cochrane Database of Systematic Reviews for the keywords: liver cirrhosis, diagnosis, treatment. 37 literary sources were selected and analyzed. Results. LC is currently ranked 11th among the most common causes of death. The common causes of LC are chronic alcohol intoxication and viral hepatitis B, C, and D. LC is represented by an increase in severity, which is characterized by the lesions of the liver parenchyma with necrosis, dystrophy of hepatocytes, their nodular regeneration, as well as its interstitium with diffuse proliferation of connective tissue, leading to liver failure and portal hypertension. Most patients with cirrhosis remain asymptomatic until they develop decompensated LC. Despite the existence of a number of LC classifications – by morphology, etiology, severity, course, hepatocellular insufficiency stage, the severity of the disease is usually assessed by evaluation of the hepatic functional reserve (according to the C. G. Child – R. N. Pugh classification). Patients with LC often have life-threatening conditions such as variceal hemorrhages, ascites, spontaneous bacterial peritonitis, hepatic encephalopathy, hepatorenal syndrome. Variceal bleeding is a major complication of portal hypertension, which is associated with significant mortality. Ascites represents the most common decompensating event in patients with LC. The appearance of ascites is strongly related to portal hypertension, which leads to splanchnic arterial vasodilation, reduction of the effective circulating volume, activation of endogenous vasoconstrictor systems, and avid sodium and water retention in the kidneys. Bacterial translocation further worsens hemodynamic alterations of patients with cirrhosis and ascites. Ascites is also associated with a high risk of developing the further complications of cirrhosis such as dilutional hyponatremia, spontaneous bacterial peritonitis and/or other bacterial infections and acute kidney injury. Pharmacotherapy for LC should be implemented in accordance with up-to-date guidelines and in conjunction with etiology management, nutritional optimization and patients’ education. The main treatment of uncomplicated ascites is diuretics such as spironolactone in combination with a loop one. Vasoconstrictors and albumin are recommended for the treatment of refractory ascites. In its turn antibiotics play a well-established role in the treatment and prevention of spontaneous bacterial peritonitis. The administration of vasopressor terlipressin and albumin is recommended for the treatment of hepatorenal syndrome. Pharmacological therapy of variceal bleeding aims to decrease the portal pressure by acting on its pathophysiological mechanisms such as increased hepatic vascular tone and splanchnic vasodilatation. Propranolol blocks the β-1 in the heart and the peripheral β-2 adrenergic receptors. β-1 blockade of cardiac receptors reduces heart rate, cardiac output and subsequently decreases flow into splanchnic circulation. β-2 blockade leads to unopposed α-1 adrenergic activity that causes splanchnic vasoconstriction and reduction of portal inflow. Both effects contribute to reduction in portal pressure. Carvedilol is more powerful in reducing hepatic venous pressure gradient than traditional nonselective β-blockers. Endoscopic treatment in many cases is used for the variceal bleeding (eg., ligation of the esophageal varices and tissue glue usage for the gastric varices). A shunt (transjugular intrahepatic portosystemic shunting – TIPS) is used to treat severe and often repeat variceal hemorrhage or refractory ascites. Non-selective β-blockers effectively reduce variceal re-bleeding risk in LC patients with moderate/large varices. Conclusions. Liver cirrhosis is one of the most dangerous multi-organ diseases of a human with multiple pathogenetic links, the causes of which invariably remain hepatitis viruses, alcohol, toxic substances, drugs, ultraviolet radiation, genetic factors, some chronic diseases of the internal organs. There are a number of classifications of liver cirrhosis – by morphology, etiology, severity, course, severity of hepatocellular insufficiency etc. Examination of this category of patients requires timeliness, scrupulousness, compliance with a comprehensive approach using modern clinical, laboratory and instrumental methods. During the objective examination of a patient a doctor traditionally draws attention to the presence of telangiectasia, palmar erythema, jaundice, “raspberry” tongue, scratching marks, gynecomastia in men, ascites and “caput medusae”, during the palpation the liver is enlarged, dense, with a sharp lower edge, spleen is enlarged. Among the laboratory methods, in addition to routine ones, the immunological tests are used, among the main instrumental examination – ultrasound, computed tomography, indirect elastometry of the liver or Fibroscan, esophagogastrofibroscopy, puncture biopsy of the liver, in particular modern ones – vibrational transient elastography and magnetic resonance elastography. Although liver cirrhosis is the final stage of liver disease, this diagnosis cannot be considered a verdict for a patient, because today there are quite effective treatments using the principles of differentiation – the impact on the etiological factor, liver state and comorbid lesions and their complications often allows if not to cure the patient, then to prevent the negative disease course. Among them, there are diet, the use of etiotropic drugs, intestinal sanitation, correction of clinical and laboratory syndromes, portal hypertension syndrome, endothelial and autonomic dysfunction as causes of comorbid lesions and their complications.


2006 ◽  
Vol 290 (5) ◽  
pp. G980-G987 ◽  
Author(s):  
Juan G. Abraldes ◽  
Yasuko Iwakiri ◽  
Mauricio Loureiro-Silva ◽  
Omar Haq ◽  
William C. Sessa ◽  
...  

Increased nitric oxide (NO) is the main factor leading to the hyperdynamic circulation associated with advanced portal hypertension (PHT), but the initial mechanisms and the magnitude of increase in portal pressure required to trigger NO production are not known. We addressed these issues by studying systemic and splanchnic hemodynamics and endothelial NO synthase (eNOS) and VEGF expression in rats with different degrees of portal hypertension. Portal vein ligation (PVL) performed over needles of three different calibers (16-, 18-, and 20-gauge) yielded different degrees of PHT and portosystemic shunting. Compared with sham rats, all three groups of PVL rats exhibited features of hyperdynamic circulation. Rats with minimal portal hypertension (PVL with a 16-gauge needle) showed an early increase in VEGF and eNOS expression selectively at the jejunum. Immunofluorescence showed that VEGF expression was located in highly vascularized areas of the mucosa. Inhibition of VEGF signaling markedly attenuated the increase in eNOS expression. In conclusion, mild increases in portal pressure are enough to upregulate eNOS at the intestinal microcirculation, and this occurs, at least in part, through VEGF upregulation.


2008 ◽  
Vol 294 (6) ◽  
pp. G1311-G1317 ◽  
Author(s):  
Claire Edwards ◽  
Hong-Qiang Feng ◽  
Christopher Reynolds ◽  
Lan Mao ◽  
Don C. Rockey

Reduced sinusoidal endothelial nitric oxide (NO) production contributes to increased intrahepatic resistance and portal hypertension after liver injury. We hypothesized that V-PYRRO/NO, an NO donor prodrug metabolized “specifically” in the liver, would reduce portal venous pressure (PVP) without affecting the systemic vasculature. Liver injury was induced in male BALB/c mice by weekly CCl4gavage. PVP and mean arterial pressure were recorded during intravenous administration of V-PYRRO/NO. In vivo microscopy was used to monitor sinusoidal diameter and flow during drug administration. Mean PVP was increased in CCl4-treated mice compared with sham-treated mice. In dose-response experiments, the minimum dose of PYRRO/NO required to acutely lower PVP by 20%, the amount believed to yield a clinically meaningful outcome, was 200 nmol/kg. This dose decreased portal pressure in cirrhotic (23.4 ± 2.0%, P < 0.001 vs. vehicle) and sham-treated (19.5 ± 2.3%, P < 0.001 vs. vehicle) animals by a similar magnitude. This concentration also led to dilation of hepatic sinusoids and an increase in sinusoidal volumetric flow, consistent with a reduction of intrahepatic resistance. The effect of V-PYRRO/NO on mean arterial pressure was significant at all concentrations tested, including the lowest, 30 nmol/kg ( P < 0.001 vs. vehicle for all doses). We conclude that V-PYRRO/NO had widespread vascular effects and, as such, is unlikely to be suitable for treatment of portal hypertension. As the potential of this or other similar compounds for treatment of portal hypertension is evaluated, effects on the systemic vasculature will also need to be considered.


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