Nitric oxide-deficiency regulates hepatic heme oxygenase-1

Activation of NLRP3 Inflammasome in Liver of Long Evans Lactating Rats and Its Perinatal Effects in the Offspring after Bisphenol F Exposure

The liver is the organ responsible for the metabolism and detoxification of BPF, the BPA analogue that is replacing it in plastic-based products. It is not known whether BPF can trigger inflammatory responses via the NLRP3 inflammasome, which plays a major role in the development of liver disease. The aim of this study was to evaluate nitrosative stress species (RNS) and NLRP3 inflammasome activation in the liver of lactating dams after BPF exposure. Moreover, it was studied whether this effect could also be observed in the liver of female and male offspring at postnatal day 6 (PND6). 36 Long Evans rats were randomly distributed according to oral treatment into three groups: Control, BPF-low dose (LBPF; 0.0365 mg/kg b.w./day) group and BPF-high dose (HBPF; 3.65 mg/kg b.w./day) group. The levels of nitrosative stress-inducing proteins (eNOS, iNOS, HO-1d), NLRP3 inflammasome components (NLRP3, PyCARD, CASP1) and proinflammatory cytokines (IL-1β, IL-18, IFN-γ and TNF-α) were measured by gene and protein expression in the liver of lactating dams and in female and male PND6 offspring. Lactating dams treated with LBPF showed a significant increase in iNOS and HO-1d, activation of NLRP3 components (NLRP3, PyCARD, CASP1) and promoted the release of proinflammatory cytokines such as IL-1β, IL-18, IFN-γ and TNF-α. Similar effects were found in female and male PND6 offspring after perinatal exposure. LBPF oral administration and perinatal exposure caused an increase of nitrosative stress markers and proinflammatory cytokines. Also, NLRP3 inflammasome activation was significantly increased in in the liver of lactating dams and PND6 offspring.

Anti-inflammatory Effects of Heme Oxygenase-1 Depend on Adenosine A2A- and A2B-Receptor Signaling in Acute Pulmonary Inflammation

Acute pulmonary inflammation is still a frightening complication in intensive care units. In our previous study, we determined that heme oxygenase (HO)-1 had anti-inflammatory effects in pulmonary inflammation. Recent literature has emphasized a link between HO-1 and the nucleotide adenosine. Since adenosine A_2A- and A_2B-receptors play a pivotal role in pulmonary inflammation, we investigated their link to the enzyme HO-1. In a murine model of pulmonary inflammation, the activation of HO-1 by hemin significantly decreased polymorphonuclear leukocyte (PMN) migration into the lung. This anti-inflammatory reduction of PMN migration was abolished in A_2A- and A_2B-knockout mice. Administration of hemin significantly reduced chemokine levels in the BAL of wild-type animals but had no effects in A_2A^-/- and A_2B^-/- mice. Microvascular permeability was significantly attenuated in HO-1-stimulated wild-type mice, but not in A_2A^-/- and A_2B^-/- mice. The activity of HO-1 rose after LPS inhalation in wild-type animals and, surprisingly, also in A_2A^-/- and A_2B^-/- mice after the additional administration of hemin. Immunofluorescence images of animals revealed alveolar macrophages to be the major source of HO-1 activity in both knockout strains—in contrast to wild-type animals, where HO-1 was also significantly augmented in the lung tissue. In vitro studies on PMN migration further confirmed our in vivo findings. In conclusion, we linked the anti-inflammatory effects of HO-1 to functional A_2A/A_2B-receptor signaling under conditions of pulmonary inflammation. Our findings may explain why targeting HO-1 in acute pulmonary inflammation has failed to prove effective in some patients, since septic patients have altered adenosine receptor expression.

Effect of morin, a flavonoid against DOCA-salt hypertensive rats: a dose dependent study

OBJECTIVE

To determine the protective effect of morin, a flavonoid against deoxycorticosterone acetate (DOCA)-salt induced hypertension in male Wistar rats.

METHODS

Hypertension was induced in uninephrectomized rats by weekly twice subcutaneous injection of DOCA (25 mg/kg bw) and 1% NaCl in the drinking water for six consecutive weeks. Effect of morin against DOCA-salt induced hypertension was evaluated by measuring blood pressure and performing biochemical estimations and histopathological examination of renal tissues.

RESULTS

DOCA-salt hypertensive rats showed considerably increased systolic and diastolic blood pressure, serum hepatic marker enzyme activities such as aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and gamma-glutamyl transpeptidase (GGT) and renal function markers (urea, uric acid and creatinine) in plasma. Oral administration of morin (25, 50 and 75 mg/kg bw) brought back all the above parameters to near normal level. Histopathology of kidney also confirmed the biochemical findings of this study. The effect at a dose of 50 mg/kg bw of morin was more pronounced than that of the other two doses (25 and 75 mg/kg bw).

CONCLUSIONS

These findings indicate that morin exhibits strong antihypertensive effect against DOCA-salt induced hypertension.

Momordin Ic induces HepG2 cell apoptosis through MAPK and PI3K/Akt-mediated mitochondrial pathways

Momordin Ic is a natural triterpenoid saponin enriched in various Chinese and Japanese natural medicines such as the fruit of Kochia scoparia (L.) Schrad. So far, there is little scientific evidence for momordin Ic with regard to the anti-tumor activities. The aim of this work was to elucidate the anti-tumor effect of momordin Ic and the signal transduction pathways involved. We found that momordin Ic induced apoptosis in human hepatocellular carcinoma HepG2 cells, which were supported by DNA fragmentation, caspase-3 activation and PARP cleavage. Meanwhile, momordin Ic triggered reactive oxygen species (ROS) production together with collapse of mitochondrial membrane potential, cytochrome c release, down-regulation of Bcl-2 and up-regulation of Bax expression. The activation of p38 and JNK, inactivation of Erk1/2 and Akt were also demonstrated. Although ROS production rather than NO was stimulated, the expression of iNOS and HO-1 were altered after momordin Ic treatment for 4 h. Furthermore, the cytochrome c release, caspase-3 activation, Bax/Bcl-2 expression and PARP cleavage were promoted with LY294002 and U0126 intervention but were blocked by SB203580, SP600125, PI3K activator, NAC and 1,400 W pretreatment, demonstrating the mitochondrial disruption. Furthermore, momordin Ic combination with NAC influenced MAPK, PI3K/Akt and HO-1, iNOS pathways, MAPK and PI3K/Akt pathways also regulated the expression of HO-1 and iNOS. These results indicated that momordin Ic induced apoptosis through oxidative stress-regulated mitochondrial dysfunction involving the MAPK and PI3K-mediated iNOS and HO-1 pathways. Thus, momordin Ic might represent a potential source of anticancer candidate.

[Small-for-size: experimental findings for liver surgery]

The characteristics of the hepatic macrocirculation, i.e., the parallel portal-venous and arterial blood supply, is of utmost relevance for liver surgery. With extended hepatectomy or transplantation of a reduced-size liver the remaining or transplanted liver tissue is overperfused because the liver fails to regulate the portal-venous inflow. This portal hyperperfusion is responsible for the initiation of liver cell proliferation but represents at the same time one of the substantial events in the pathogenesis of the small-for-size syndrome. Portal-venous hyperperfusion, the so-called hepatic arterial buffer response, which describes the semi-reciprocal relationship between the portal-venous and hepatic arterial blood flows, leads to an arterial hypoperfusion of the small-for-size liver. In this article experimental and clinical data are discussed which underline the high but so far overseen relevance of this arterial underperfusion in the development of a small-for-size syndrome.

Antihypertensive and antioxidant potential of vanillic acid, a phenolic compound in L-NAME-induced hypertensive rats: a dose-dependence study

We investigated the antihypertensive and antioxidant potential of vanillic acid (VA) in N(ω)-Nitro-L-arginine methyl ester hydrochloride (L-NAME) - treated adult male albino Wistar rats. Treatment of rats with L-NAME (40 mg/kg Bw for 30 days) caused a sustained increase in systolic- (SBP) and diastolic blood pressure (DBP) and significantly decreased the concentration of nitrite/nitrate (NO(x)) in plasma as compared with that in the control. Rats treated with VA restored SBP and DBP to normal level and preserve the plasma NO metabolites concentration. Moreover, VA reduced lipid peroxidation products (thiobarbituric acid reactive substances, lipid hydroperoxides, conjugated dienes) and significantly restored enzymatic antioxidants (superoxide dismutase, catalase, and glutathione peroxidase), non-enzymatic antioxidants (vitamin C, vitamin E, and reduced glutathione) in the plasma. To assess the toxicity if any of VA treatment, hepatic and renal function markers were measured. Our results showed that the effect at a dose of 50 mg/kg Bw of VA was more pronounced than that of the other two doses, 25 and 100 mg/kg Bw. These results were supported by histopathology studies. We conclude that VA possesses an antihypertensive and antioxidant activity in L-NAME-induced hypertensive rats.

Effects of catechin-rich oil palm leaf extract on normal and hypertensive rats' kidney and liver

Catechin-rich oil palm (Elaeis guineensis) leaf extract (OPLE) possesses good ex vivo vasodilation, antioxidant and cardiovascular properties. This study evaluated the beneficial or toxic effects of OPLE on the liver and kidneys of normal and hypertensive rats. The OPLE (500mg/kg body weight) were administered orally to normal Wistar Kyoto rats, spontaneously hypertensive rats (SHR) and N-ω-nitro-l-arginine methyl ester (l-NAME)-induced NO-deficient hypertensive rats. The OPLE reduced hypertension in NO-deficient rats, but not in SHR. Hepatocytes or glomeruli injury and oxidative markers were high in hypertensive rats compared to normal rats, and they were reduced (p<0.05) by OPLE supplementation, even when there was no blood pressure reduction. Unlike the hypertensive drug captopril, the OPLE showed no toxicity to normal rats. The dose reported is equivalent 0.5g of catechins/day for humans or 2.5cups of tea. The catechins are from an abundant alternative source for potential use as functional food.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Applying gases for microcirculatory and cellular oxygenation in sepsis: effects of nitric oxide, carbon monoxide, and hydrogen sulfide

PURPOSE OF REVIEW

Nitric oxide, carbon monoxide, and hydrogen sulfide (H2S) are gases that have received attention as signaling molecules regulating many biological processes. All of them were reported to have beneficial effects in inflammatory states, in particular for microcirculatory perfusion and tissue energy balance. Thus, this review will highlight the most important results with a focus on resuscitated, clinically relevant experimental models and, if available, human studies.

RECENT FINDINGS

There is ample evidence that nitric oxide, carbon monoxide, and H2S may exert cytoprotective effects in shock states due to their vasomotor, antioxidant, and anti-inflammatory properties as well as their potential to induce a hibernation-like metabolic state called 'suspended animation' resulting from inhibition of cytochrome-c-oxidase. It must be emphasized, however, that the three molecules may also be cytotoxic, not only because of their inhibition of cellular respiration but also because of their marked pro-inflammatory effects.

SUMMARY

It is still a matter of debate whether manipulating nitric oxide, carbon monoxide, or H2S tissue concentrations, either by using the inhaled gas itself or by administering donor molecules or inhibitors of their endogenous production, is a useful therapeutic approach to improve microcirculatory blood flow, tissue oxygenation, and cellular respiration. This is mainly due to their 'friend and foe character' documented in various experimental models, but also to the paucity of data from long-term, resuscitated large animal experiments that fulfil the criteria of clinically relevant models.

Phosphodiesterase-5 inhibitors have distinct effects on the hemodynamics of the liver

BACKGROUND

The NO--cGMP system plays a key role in the regulation of sinusoidal tonus and liver blood flow with phosphodiesterase-5 (PDE-5) terminating the dilatory action of cGMP. We, therefore, investigated the effects of PDE-5 inhibitors on hepatic and systemic hemodynamics in rats.

METHODS

Hemodynamic parameters were monitored for 60 min. after intravenous injection of sildenafil and vardenafil [1, 10 and 100 microg/kg (sil1, sil10, sil100, var1, var10, var100)] in anesthetized rats.

RESULTS

Cardiac output and heart rate remained constant. After a short dip, mean arterial blood pressure again increased. Systemic vascular resistance transiently decreased slightly. Changes in hepatic hemodynamic parameters started after few minutes and continued for at least 60 min. Portal (var10 -31%, sil10 -34%) and hepatic arterial resistance (var10 -30%, sil10 -32%) decreased significantly (p < 0.05). At the same time portal venous (var10 +29%, sil10 +24%), hepatic arterial (var10 +34%, sil10 +48%), and hepatic parenchymal blood flow (var10 +15%, sil10 +15%) increased significantly (p < 0.05). The fractional liver blood flow (total liver flow/cardiac output) increased significantly (var10 26%, sil10 23%). Portal pressure remained constant or tended to decrease. 10 microg/kg was the most effective dose for both PDE-5 inhibitors.

CONCLUSION

Low doses of phosphodiesterase-5 inhibitors have distinct effects on hepatic hemodynamic parameters. Their therapeutic use in portal hypertension should therefore be evaluated.

Role of gaseous signal molecules in the development of hepatic cirrhosis with portal hypertension

Nitrogen monoxide, carbon monoxide and hydrogen sulfide are three types of endogenous gas molecules that are able to exert diverse biological effects. As they can dilate blood vessels and suppress platelet aggregation and cell multiplication, the research on these gas signal molecules has become active. Their role in the development of hepatic cirrhosis with portal hypertension has gradually attracted more attention. Here, we will review the role of these gas signal molecules in the development of hepatic cirrhosis with portal hypertension.