Colchicine inhibits lithocholate-3-O-glucuronide-induced cholestasis in rats

Remodeling of the gut microbiome by Lactobacillus johnsonii alleviates the development of acute myocardial infarction

Introduction

The gut microbial community, which can be disturbed or repaired by changes in the internal environment, contributes to the development of acute myocardial infarction (AMI). Gut probiotics play a role in microbiome remodeling and nutritional intervention post-AMI. A newly isolated Lactobacillus johnsonii strain EU03 has shown potential as a probiotic. Here, we investigated the cardioprotective function and mechanism of L. johnsonii through gut microbiome remodeling in AMI rats.

Methods

A rat model of left anterior descending coronary artery ligation (LAD)-mediated AMI was assessed with echocardiography, histology, and serum cardiac biomarkers to evaluate the beneficial effects of L. johnsonii. The immunofluorescence analysis was utilized to visualize the intestinal barrier changes. Antibiotic administration model was used for assessing the gut commensals’ function in the improvement of cardiac function post-AMI. The underlying beneficial mechanism through L. johnsonii enrichment was further investigated by metagenomics and metabolomics analysis.

Results

A 28-day treatment with L. johnsonii protected cardiac function, delayed cardiac pathology, suppressed myocardial injury cytokines, and improved gut barrier integrity. The microbiome composition was reprogrammed by enhancing the abundance of L. johnsonii. Microbiome dysbiosis by antibiotics abrogated the improvement of cardiac function post-AMI by L. johnsonii. L. johnsonii enrichment caused remodeling of gut microbiome by increasing the abundance of Muribaculaceae, Lactobacillus, and decreasing Romboutsia, Clostridia UCG-014, which were correlated with cardiac traits and serum metabolic biomarkers 16,16-dimethyl-PGA2, and Lithocholate 3-O-glucuronide.

Conclusion

These findings reveal that gut microbiome remodeling by L. johnsonii ameliorates the cardiac function post-AMI and might advance microbiome-targeted nutritional intervention.

Altered circadian hemodynamic and renal function in cirrhosis

Background

Given that alterations in systemic hemodynamics have a profound influence on renal function in patients with cirrhosis, it is surprising that circadian variations in blood pressure (BP) and renal electrolyte excretion have scarcely been studied. Our aims were to define the relationship of 24-h ambulatory BP changes with renal tubular function and to determine the influence of endotoxemia on BP and urinary parameters.

Methods

Forty healthy controls served as a comparator to 20 cirrhotic patients. They underwent 24-h ambulatory BP monitoring and 24-h urine collection.

Results

Subjects with cirrhosis demonstrated significant diurnal variations in urinary excretion of sodium (57.7 µmol/min day versus 87 µmol/min night) and creatinine (826 µg/min day versus 1202 µg/min night). Increasing severity of cirrhosis was associated with a progressive reduction in ambulatory awake systolic (P-trend = 0.015), diastolic (P-trend < 0.001) and mean BP (P-trend < 0.001). In patients with cirrhosis, the magnitude of change in BP from awake to sleep state was blunted for systolic BP (5% reduction, P = 0.039) and pulse rate (2% reduction, P < 0.001). The amplitude of variation in pulse rate was blunted with increasing severity of cirrhosis (controls 6.5, Child-Pugh Class A 5.3, Child B 3.4, Child C 1.2, P = 0.03) and the acrophase was right-shifted with increasing severity of cirrhosis. Compared with sleep state, during the awake state, endotoxin was associated with less sodium excretion and a lower systolic BP. Compared with the awake state, endotoxin was associated with a higher sleeping pulse rate (P < 0.001).

Conclusions

Patients with cirrhosis have altered diurnal profiles in renal tubular function and blood pressure that appear to be related to endotoxemia. Determining whether endotoxemia is causally related to these perturbations will require interventional studies.

Role of glucuronidation for hepatic detoxification and urinary elimination of toxic bile acids during biliary obstruction

Biliary obstruction, a severe cholestatic condition, results in a huge accumulation of toxic bile acids (BA) in the liver. Glucuronidation, a conjugation reaction, is thought to protect the liver by both reducing hepatic BA toxicity and increasing their urinary elimination. The present study evaluates the contribution of each process in the overall BA detoxification by glucuronidation. Glucuronide (G), glycine, taurine conjugates, and unconjugated BAs were quantified in pre- and post-biliary stenting urine samples from 12 patients with biliary obstruction, using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The same LC-MS/MS procedure was used to quantify intra- and extracellular BA-G in Hepatoma HepG2 cells. Bile acid-induced toxicity in HepG2 cells was evaluated using MTS reduction, caspase-3 and flow cytometry assays. When compared to post-treatment samples, pre-stenting urines were enriched in glucuronide-, taurine- and glycine-conjugated BAs. Biliary stenting increased the relative BA-G abundance in the urinary BA pool, and reduced the proportion of taurine- and glycine-conjugates. Lithocholic, deoxycholic and chenodeoxycholic acids were the most cytotoxic and pro-apoptotic/necrotic BAs for HepG2 cells. Other species, such as the cholic, hyocholic and hyodeoxycholic acids were nontoxic. All BA-G assayed were less toxic and displayed lower pro-apoptotic/necrotic effects than their unconjugated precursors, even if they were able to penetrate into HepG2 cells. Under severe cholestatic conditions, urinary excretion favors the elimination of amidated BAs, while glucuronidation allows the conversion of cytotoxic BAs into nontoxic derivatives.

Effect of genipin on cholestasis induced by estradiol-17beta-glucuronide and lithocholate-3-O-glucuornide in rats

AIM

Genipin is reported to stimulate the insertion of multidrug resistance protein 2 (Mrp2) in the bile canalicular membrane, thereby causing choleresis by the increased the biliary excretion of glutathione, which has been considered to be a substrate of Mrp2. In the present study, we examined the effect of genipin on cholestasis induced by estradiol-17beta-glucuronide and lithocholate-3-O-glucuronide, Mrp2 substrates, in rats. Further, the effect of genipin on the biliary excretion of substrates of P-glycoprotein (P-gp), vinblastine and erythromycin, was also studied.

METHODS

The effect of genipin infusion at the rate of 0.5 micromol/min/100 g on cholestasis induced by estradiol-17beta-glucuronide (0.075 micromol/min/100 g for 20 min) and lithocholate-3-O-glucuronide (0.15 micromol/min/100 g for 40 min) was studied. The effect of genipin infusion on the biliary excretion of a tracer dose of vinblastine and erythromycin infused at the rate of 0.1 micromol/min/100 g was also studied.

RESULTS

Genipin relieved estradiol-17beta-glucuronide-induced cholestasis, and cumulative biliary estradiol-17beta-glucuronide excretion for 120 min was increased from 50 +/- 20%-81 +/- 20% dose. In contrast, genipin had no effect on lithocholate-3-O-glucuronide-induced cholestasis. Biliary excretion of a tracer dose of vinblastine and the maximum biliary excretion of erythromycin were significantly decreased by genipin.

CONCLUSIONS

Genipin protected estradiol-17beta-glucuronide-induced cholestasis. The mechanism of the protection of cholestasis by genipin is unknown, but it is speculated to be due to a conformational change of P-gp by genipin, in addition to the stimulation of Mrp2 insertion into the bile canaliculi.

BNP and N-terminal proBNP are both extracted in the normal kidney

BACKGROUND

Increased plasma concentrations of cardiac-derived B-type natriuretic peptide (BNP) and N-terminal pro-B-type natriuretic peptide (proBNP) are both associated with left ventricular dysfunction. Information on the regional elimination of the peptides is, however, still scarce. We therefore examined the renal and peripheral extraction of N-terminal proBNP and BNP.

MATERIALS AND METHODS

The study comprised 18 patients with essential arterial hypertension, 51 with cirrhosis, and 18 control patients without kidney or liver disease. All patients underwent a haemodynamic investigation with catheterization of the femoral artery and femoral and renal veins. Blood sampling from the catheters allowed determination of the arteriovenous extraction ratio of N-terminal proBNP and BNP.

RESULTS

Neither the peripheral N-terminal proBNP (13, 11, 19 pmol L(-1), NS) nor the BNP plasma concentrations (4, 12, 9 pmol L(-1), NS) differed between the patient groups. In addition, similar renal extractions were observed in the groups. The renal extraction of N-terminal proBNP (0.16) was not different from that of BNP (0.16). In contrast, the N-terminal proBNP extraction in the lower extremity was markedly lower compared with BNP (0.00 vs. 0.125, P = 0.007).

CONCLUSIONS

A comparable renal elimination of N-terminal proBNP and BNP is contrasted by a selective extraction of BNP in the lower extremity. Our results suggest a different elimination mechanism in the renal and peripheral circulation, which partly may explain the higher N-terminal proBNP compared with BNP concentrations in normal plasma.

Effects of colchicine on the maximum biliary excretion of cholephilic compounds in rats

BACKGROUND AND AIM

Colchicine, an inhibitor of intracellular vesicular transport, has been reported to inhibit the biliary excretion of bile acids and organic anions, but the previous findings are controversial. In order to systematically evaluate the effect of colchicine on the biliary excretion of cholephilic compounds, we studied the effect of colchicine on the biliary excretion of substrates of various canalicular transporters, which were administered at or above the excretory maximum in rats.

METHODS

Substrates of various canalicular adenosine triphosphate-binding-cassette transporters were infused at or above the rate of maximum excretion into rats, and the effect of colchicine (0.2 mg/100 g), which was intraperitoneally injected 3 h before, on the biliary excretion was studied. Furthermore, the effect of tauroursodeoxycholate (TUDC) co-infusion on the biliary excretion of taurocholate (TC) after colchicine treatment was also studied.

RESULTS

The biliary excretion of TC and cholate administered at the rate of 1 micro mol/min/100 g was markedly inhibited by colchicine, whereas that of TUDC was not inhibited even with the infusion rate of 2 micro mol/min/100 g. TUDC co-infusion at the rate of 1 micro mol/min/100 g increased the biliary excretion of TC (1 micro mol/min/100 g), which was decreased by the colchicine pretreatment. The biliary excretory maximum of taurolithocholate-sulfate and sulfobromophthalein, substrates of the multidrug resistance protein 2, of erythromycin, a substrate of the P-glycoprotein, and of indocyanine green were not affected by colchicine.

CONCLUSIONS

The different excretory maximums of TC and TUDC and the different effect of colchicine on the excretion of these bile acids are considered to be a result of different regulatory mechanisms of vesicular targeting of the bile salt export pump to the canalicular membrane by these bile acid conjugates. The vesicular targeting of the multidrug resistance protein 2 and the P-glycoprotein to the canalicular membrane is considered to be colchicine insensitive in the absence of bile acid coadministration.

Cirrhosis does not shift the circadian phase of plasma fibrinolysis

OBJECTIVES

The aim of the present investigation was to study the endogenous circadian clock phase rhythm in cirrhotic patients.

METHODS

The study population comprised 13 patients with cirrhosis (seven in Child-Pugh class A and six in classes B/C) and nine healthy controls. Plasma melatonin, tissue plasminogen activator antigen, and plasminogen activator inhibitor 1 antigen were measured at 4-h intervals over a 24-h period. Multiple-components rhythmometry using population mean cosinor methods were employed to analyze the findings.

RESULTS

All three variables were characterized in both patients and controls by a statistically significant circadian rhythm, with similar profiles. The peak times of tissue plasminogen activator and plasminogen activator inhibitor 1 antigens were practically identical in controls and cirrhotic patients, irrespective of Child-Pugh class (calculated peak at times 6:52, 6:56, and 7:20 for the inhibitor in controls and Child-Pugh class A and classes B/C patients, respectively; p = ns), whereas the peak of melatonin was delayed in classes B/C patients (at times 2:08, 1:56, and 4:00, respectively; p < 0.05).

CONCLUSION

The similar circadian phases of plasminogen activator inhibitor antigen in controls and cirrhotic patients in the present investigation indicates that the output rhythm of the internal timekeeping system is not shifted in this pathological condition.

DNA vaccines for hepatitis C virus

Hepatitis C virus is an RNA encoded virus of the Flaviviridae family. In most cases, infections develop into a chronic carrier stage that can result in the onset of cirrhosis and hepatocellular carcinoma over a 20- to 30-year period. Because existing therapies are still of limited benefit and expensive, the development of a vaccine represents a priority to prevent further spreading of the infection. Immune correlates of protection remain poorly defined although increasing evidence suggests that both humoral and cellular immune responses are likely to contribute to protection and/or neutralization of the virus. Current DNA-based vaccines, while capable of generating the latter, appear limited in their capacity to induce a strong and long-lasting antibody response.

Nitric oxide may contribute to nocturnal hemodynamic changes in cirrhotic patients

OBJECTIVE

Patients with liver cirrhosis have a nocturnal worsening of hemodynamic parameters that has been associated with an increased risk of variceal bleeding at nighttime. The aim of this study was to investigate whether nitric oxide and cytokines are implicated in these hemodynamic changes.

METHODS

Ten cirrhotic patients and eight controls were studied. Mean blood pressure, heart rate, plasma norepinephrine, tumor necrosis factor alpha and interleukin-6 levels, and serum nitrite + nitrate levels were determined at 0800, 1600, and 2400 h. All determinations were performed in supine rest and at least 4 h after meals. In a second study, nitrite + nitrate levels were assessed in 10 cirrhotic patients before and after eating a standard meal.

RESULTS

Mean arterial pressure levels that were always lower in the patient group showed a nocturnal decrease in both groups of subjects. Heart rate values that were always higher in cirrhotic patients showed a nocturnal fall in controls, whereas cirrhotics maintained elevated values at nighttime. Norepinephrine levels were higher in cirrhotics and maintained similar values during the study, whereas controls had a significant nocturnal decrease. Nitrite + nitrate levels that were higher in cirrhotic patients showed a significant mean increase of 40% from morning (0800 h) to night (2400 h) in the patient group, whereas in controls no change was observed (p < 0.05). Tumor necrosis factor alpha and interleukin-6 levels did not change either in patients or controls during the entire period. Cirrhotic patients with or without ascites maintained a pattern of hemodynamic and biochemical changes similar to the pattern observed in the entire group of patients. Finally, no changes in serum nitrite + nitrate levels were observed in patients before and after eating the standard meal.

CONCLUSION

An increased nocturnal nitric oxide production might contribute to the hemodynamic changes observed in cirrhotic patients during nighttime.

Effects of organic anions and vinblastine on biliary excretion of erythromycin in rats

Since little is known about the mechanism of biliary excretion of cationic drugs, biliary excretion of erythromycin was studied in rats. Infusion of sulfobromophthalein and taurocholate significantly decreased biliary erythromycin excretion, whereas infusion of dibromosulfophthalein, cefpiramide, ursodeoxycholate-3-O-glucuronide and taurolithocholate-3-sulfate had no effect on biliary excretion of erythromycin. Vinblastine significantly inhibited biliary erythromycin excretion. Phenothiazine treatment significantly increased biliary erythromycin excretion. However, erythromycin infusion did not affect biliary vinblastine excretion. These findings indicate a multiplicity of biliary excretory pathways for organic cations; at least one additonal pathway may exist for organic cations apart from P-glycoprotein.

Effects of colchicine and phenothiazine on biliary excretion of organic anions in rats

Vesicular transport inhibitors have been reported to inhibit biliary excretion of some organic anions, suggesting that vesicular transport has a role in intracellular transport of these compounds. However, these inhibitors are substrates for P-glycoprotein. To examine whether P-glycoprotein has a role in canalicular transport of organic anions in addition to the canalicular multispecific organic anion transporter, we studied the effect of colchicine, a vesicular transport inhibitor, and phenothiazine to increase P-glycoprotein expression on biliary excretion of various organic anions in rats. Colchicine treatment slightly but significantly inhibited biliary excretion of indocyanine green, dinitrophenyl-glutathione and pravastatin, and had no effect on biliary excretion of sulphobromophthalein and dibromosulphophthalein. Phenothiazine treatment did not affect biliary excretion of indocyanine green and pravastatin, but it increased biliary sulphobromophthalein-glutathione excretion. In conclusion, the present findings suggest that P-glycoprotein plays an additive role on biliary excretion of some organic anions in addition to the canalicular multispecific organic anion transporter.