Microbiome diversity in African American, European American, and Egyptian colorectal cancer patients

Purpose

Although there is an established role for microbiome dysbiosis in the pathobiology of colorectal cancer (CRC), CRC patients of various race/ethnicities demonstrate distinct clinical behaviors. Thus, we investigated microbiome dysbiosis in Egyptian, African American (AA), and European American (EA) CRC patients.

Patients and methods

CRCs and their corresponding normal tissues from Egyptian (n = 17) patients of the Alexandria University Hospital, Egypt, and tissues from AA (n = 18) and EA (n = 19) patients at the University of Alabama at Birmingham were collected. DNA was isolated from frozen tissues, and the microbiome composition was analyzed by 16S rRNA sequencing. Differential microbial abundance, diversity, and metabolic pathways were identified using linear discriminant analysis (LDA) effect size analyses. Additionally, we compared these profiles with our previously published microbiome data derived from Kenyan CRC patients.

Results

Differential microbiome analysis of CRCs across all racial/ethnic groups showed dysbiosis. There were high abundances of Herbaspirillum and Staphylococcus in CRCs of Egyptians, Leptotrichia in CRCs of AAs, Flexspiria and Streptococcus in CRCs of EAs, and Akkermansia muciniphila and Prevotella nigrescens in CRCs of Kenyans (LDA score >4, adj. p-value <0.05). Functional analyses showed distinct microbial metabolic pathways in CRCs compared to normal tissues within the racial/ethnic groups. Egyptian CRCs, compared to normal tissues, showed lower l-methionine biosynthesis and higher galactose degradation pathways.

Conclusions

Our findings showed altered mucosa-associated microbiome profiles of CRCs and their metabolic pathways across racial/ethnic groups. These findings provide a basis for future studies to link racial/ethnic microbiome differences with distinct clinical behaviors in CRC.

Site of Metastases as Prognostic Factors in Unselected Population of Stage IV Non-Small Cell Lung Cancer

Background

Advanced stage non-small cell lung cancer (NSCLC) is a heterogenous disease, yet, with the exception of targeted therapies, most guidelines recommended uniform treatment irrespective of tumor burden or sites of metastases and this may explain, in part, the wide range of responses to same lines of therapy.

Aim of work

In this work we tried to explore the effect of metastatic sites in on overall survival (OS), in an unselected group of Non-small cell lung cancer patients who received different treatments line.

Methods

A retrospective analysis was performed on patients with stage IV NSCLC who received systemic treatment at UAB Cancer Center (NCI designated comprehensive cancer center) between 2002 to 2012. The details of sites of metastases, systemic therapy and overall survival were recorded for each patient.

Result

In 409 patients who received systemic treatment, there was statistically significant lower OS in those presenting with liver metastases (p<0.001), adrenal metastases (p=0.011) and metastases to abdominal lymph nodes (p=0.014). There was no statistically significance difference in OS in patient presenting with pleural metastases or effusion (p=0.908), metastases to heart or pericardium (p=0.654), metastases to bone (p=0.281), brain (p=0.717) or skin and subcutaneous tissue (p=0.642).

Conclusion

Intra-abdominal metastases confer a particularly poor prognosis in stage IV NSCLC treated with systemic therapy and may identify patients in whom aggressive treatment beyond first line therapy is not appropriate.

Relationship between NRAMP1 gene polymorphism and efficacy of BCG vaccine in a helminth-infected population

Infection of mothers with schistosomiasis and filariasis has been shown to influence infant responses to neonatal Bacille Calmette-Guérin (BCG) immunization. The genetic makeup of infants is also considered an important determinant for the activity of BCG vaccine. The effect of natural resistance-associated macrophage protein 1 (NRAMP1) gene polymorphism on the efficacy of BCG vaccine was examined in neonates with helminth-infected mothers (63 infants) and the results were compared with neonates of uninfected mothers (187 infants). After BCG vaccination, assessment of scar presence, tuberculin test, stool analysis, and IgE level was performed. Polymorphism of the NRAMP1 gene was investigated by PCR amplification followed by RFLP analysis. We found that patients with heterozygosity of intron 4 (GC) and/or maternal infection with helminth parasites showed reduced efficacy of BCG vaccine against tuberculosis.

Effect of artemether alone and in combination with grapefruit juice on hepatic drug-metabolising enzymes and biochemical aspects in experimental Schistosoma mansoni

Artemether is an efficacious antimalarial drug that also displays antischistosomal properties. Grapefruit juice increases the oral availability of a variety of the CYP3A4 substrates. This study was designed to evaluate the effect of repeated administration of grapefruit juice with artemether on the hepatic activities of cytochrome P-450 (CYP450) and cytochrome b5 (cyt b5), on the serum levels of some biochemical enzymes and antischistosome efficacy. Results showed that administration of grapefruit juice alone induced more inhibition in the hepatic activities of CYP450 and cyt b5 than that produced by Schistosoma mansoni infection. Moreover, it enhanced degeneration of eggs and accelerated healing of the pathological granulomatous lesions. Treatment of S. mansoni-infected mice with artemether at a total dose of 300 mg/kg resulted in total and female worm burden reductions of 66.7 and 90.1%, respectively, hence protecting the host from damage induced by schistosome eggs. Treatment of S. mansoni-infected mice with artemether at 150 mg/kg reduced the total and female worm numbers by 43.3 and 54.4%, respectively, thus somewhat ameliorating hepatic granulomatous lesions compared with the infected untreated group. This was associated with no change in the hepatic activities of CYP450 and cyt b5 and in the serum levels of total protein, albumin, globulin and alanine aminotransferase compared with the uninfected control group. Coadministration of grapefruit juice with the lower dose (150 mg/kg) of artemether eliminated eggs and granulomatous reactions. In this group, the inhibitory effects of grapefruit juice on CYP450 and cyt b5 were apparent but serum liver enzymes were unchanged compared with the uninfected control group. Coadministration of grapefruit juice with artemether achieved complete protection of the host from damage induced by schistosomal infection.

Alcohol-induced euphoria: exclusion of serotonin

During the first 30 min after acute ethanol consumption by three fasting normal male volunteers, no increase in circulating tryptophan availability to the brain occurred. On the contrary, a small decrease was observed, which became stronger subsequently. We conclude from this preliminary study that brain serotonin levels are not increased after alcohol intake by normal subjects and that, consequently, this indolylamine is unlikely to mediate the euphoric effects of alcohol.

Rat liver tryptophan pyrrolase activity and gene expression during alcohol withdrawal

Rat liver tryptophan (Trp) pyrrolase activity and gene expression were studied in relation to the alcohol-withdrawal syndrome (AWS). Both activity and gene expression were enhanced after withdrawal of ethanol-containing liquid diets and the time-course of these changes mirrored that of development and intensity of the behavioural disturbances of the AWS. By contrast, no correlation was observed between the AWS-induced behaviour and changes in activity of another hepatic glucocorticoid-inducible enzyme, tyrosine aminotransferase, and a negative correlation was noted between behaviour and the gene expression of this latter enzyme and also of that of the hepatic glucocorticoid receptor. We suggest that the metabolic consequences of activation of liver Trp pyrrolase during alcohol withdrawal may play a role in the behavioural features of the AWS.

Tryptophan metabolism in alcoholism

Studies of tryptophan (Trp) metabolism in relation to the serotonin status in alcoholism are of 2 types: (1) those related to the pharmacological effects of ethanol; (2) those concerning the serotonin status in the absence of alcohol intake. In experimental animals, acute and chronic ethanol administration and subsequent withdrawal exert a variety of effects on brain serotonin synthesis and turnover mediated by corresponding changes in Trp availability to the brain secondarily mainly to modulation of liver Trp pyrrolase (TP) activity. Alcohol-preferring mice and rats exhibit a central serotonin deficiency caused by, or in some cases associated with, a higher TP activity. Liver TP also appears to be a target of ethanol in man and evidence has recently emerged that alcoholics with positive family history are serotonin-deficient because of a lower availability of circulating Trp to the brain. Acutely, ethanol depletes brain serotonin in normal subjects, which may explain alcohol-induced aggression in susceptible individuals and also the incidence of depression in alcoholism. Trp availability to the brain is increased before the appearance of the alcohol-withdrawal syndrome in man, raising the possibility that the associated behavioural disturbances may involve the excitotoxic Trp metabolite quinolinate. Further studies of the Trp and serotonin status in relation to these important clinical features of alcohol dependence and alcoholism may therefore yield fruitful results.

Inhibition of rat liver tryptophan pyrrolase activity by fluoxetine

The present study has demonstrated the effectiveness of acute administration of fluoxetine to inhibit rat liver tryptophan pyrrolase activity. The maximum inhibition of basal liver tryptophan pyrrolase activity at 2 h after administration was observed with 1 mg/kg dose for the total enzyme and apoenzyme activities and that significant inhibition of these two activities was evident with a dose of the drug as small as 0.5 mg/kg. Serum free tryptophan concentrations were also increased using 10 mg/kg dose of fluoxetine. In view of the role of tryptophan depletion and thus 5-HT in pathophysiology of depression, it is strongly suggested that the inhibition of liver tryptophan pyrrolase activity may be a major mechanism of antidepressant action.

Colchicine therapy for hepatic murine schistosomal fibrosis: image analysis and serological study

Colchicine in a dose of 200 micrograms kg body weight/day (5 days/week) was administered to groups of Schistosoma mansoni infected mice 12 weeks post infection, either alone or following previous praziquantel therapy at the 8th week of infection. Certain groups received colchicine for 6 weeks and others received it for 10 weeks. Colchicine alone did not significantly change the light microscopic appearance of schistosomal liver fibrosis, or hepatic collagen content estimated histomorphometrically, and did not reduce the elevated IL-2 serum level. Colchicine induced hepatic injury consisted of intense inflammatory reaction in granuloma and portal tracts, hepatocytic degeneration, and elevation of serum AST and ALT levels. Colchicine seemed to postpone granulomatous reaction healing and collagen deposition rather than inhibiting collagen formation or degrading it. Colchicine inhibited proliferation of hepatocytes of infected mice by expanding G2-M phases of cell cycle, thus reduced Ag NOR count and raised cell ploidy and cyclic AMP serum level. Subsidence of schistosomal infection by praziquantel prior to colchicine therapy greatly reduced inflammatory cellular reaction, significantly diminished hepatic collagen deposition and serum IL-2 level, minimized the elevated nuclear ploidy and cyclic AMP serum level that followed colchicine therapy when administered alone.

Tryptophan metabolism in alcoholism. Tryptophan but not excitatory amino acid availability to the brain is increased before the appearance of the alcohol-withdrawal syndrome in men

Tryptophan (Trp) metabolism and disposition and excitatory and other amino acid concentrations were determined in alcohol-dependent subjects in relation to the alcohol-withdrawal syndrome (AWS). Parameters were examined in 12 alcohol-dependent male subjects, undergoing elective upper digestive tract tumour resection, and 12 age-, gender-, and medication-matched controls on three occasions: pre-operatively, post-operatively, and immediately before (i.e. within 24 h of) the appearance of the AWS. No significant differences were observed between controls and alcoholic subjects on the first or second of these occasions. On the third occasion, within 24 h of the appearance of the AWS, alcoholics showed a dramatic elevation (117%) in free serum Trp concentration and a consequent increase (111%) in the ratio of [free Trp]/[competing amino acids], which is an accurate predictor of Trp entry into the brain. Increases were also observed on this third occasion in concentrations of total Trp (49%), cortisol (123%), and norharman (137%). Concentrations of glutamate, glycine, aspartate, serine, and taurine did not differ significantly within or between the control and alcohol-dependent groups of subjects on any of the three occasions. The possible significance of the Trp and related metabolic changes in relation to the behavioural features of the AWS is discussed.

Tryptophan metabolism in male Sardinian alcohol-preferring (sP) and -non-preferring (sNP) rats

Parameters of tryptophan (Trp) and related metabolism were compared in male Sardinian alcohol-preferring (sP) and -non-preferring (sNP) rats. Liver Trp pyrrolase activity was 38-58% higher in sP than in sNP rats, and this was associated with a greater expression of the enzyme mRNA as measured by multiprobe oligonucleotide solution hybridization. Moderately (about 10-19%), but significantly, lower concentrations of free serum, total serum, and brain Trp were also observed in sP compared with sNP rats. Concentrations of whole brain 5-hydroxytryptamine (5-HT) and its major metabolite 5-hydroxyindol-3-yl-acetic acid (5-HIAA) were, however, 14-21% higher in sP rats. Serum corticosterone concentration was 18% higher in sP rats. We conclude that alcohol preference in Sardinian rats is associated with increased liver Trp pyrrolase activity and mRNA expression leading to a decrease in Trp availability to the brain. Although a simple serotonin deficiency could not be demonstrated in the whole brain, the possibility could not be ruled out that a deficiency may be present in discrete areas of the brain of the sP rat.

Alcohol, aggression and serotonin: metabolic aspects

The role of serotonin (5-hydroxytryptamine) in alcohol-induced aggressive behaviour is discussed. Considerable evidence exists in support of an association between aggression and serotonin deficiency and between aggression and alcohol consumption, and it is also known that alcohol consumption exerts major effects on serotonin metabolism. These links are synthesized into the serotonin deficiency hypothesis of alcohol-induced aggressive behaviour, which postulates that individuals susceptible to aggression after alcohol consumption exhibit a marked depletion of their brain serotonin rendering them prone to aggression in response to environmental or psychological stimuli or situations. This hypothesis has already received support from experimental studies in non-aggressive subjects, but remains to be examined in those known to be aggressive after alcohol consumption.

No early effects of electroconvulsive therapy on tryptophan metabolism and disposition in endogenous depression

The possibility that a single electroconvulsive therapy (ECT) could increase tryptophan (Trp) availability to the brain for 5-hydroxytryptamine (5-HT, serotonin) synthesis was examined in 10 depressed patients before and during the 1st hour following an ECT and in 4 control (minor ear, nose, and throat surgical) subjects receiving similar premedication. Trp availability to the brain, expressed as the serum Trp: competing amino acid ratio, and related aspects of Trp disposition were not significantly altered by ECT any differently than from preoperative stress and premedication. We suggest that Trp availability to the brain and, hence, cerebral 5-HT synthesis are not altered in depressed patients early after a single ECT.

Evaluation of colchicine with or without praziquantel therapy in the control of hepatic fibrosis in murine schistosomiasis

Colchicine alone or following praziquantel was given to mice infected with Schistosoma mansoni either 6 or 10 weeks post infection. Praziquantel increased body weight gain, histologically reduced number, diameter and cellularity of granuloma and improved liver function parameters. Early praziquantel therapy decreased hepatic collagen content as detected by the colorimetric method and the serum procollagen propeptide (PIIIP), while later treatment at the 10th week of infection increased hepatic collagen content and serum PIIIP. Colchicine therapy significantly decreased body weight gain with significant weight loss after early treatment. Colchicine did not change the histologic picture of schistosomal liver fibrosis; it induced a detectable hepatocytic injury recorded ultrastructurally and histologically with excitation of the inflammatory reaction in the granuloma and in portal tracts after early treatment. Excess pigmentation in macrophages and Kupffer cells, binucleation and large sized hepatocytic nuclei were evident after colchicine therapy. Colchicine increased hepatic collagen content microgram/mg protein, raised globulin and total serum protein and normalized the raised serum PIIIP of infected mice, but had no effect on PIIIP of normal mice. Early cessation of schistosomal infection evidently minimized the adverse effects of colchicine.

Prevention by cycloheximide of the audiogenic seizures and tryptophan metabolic disturbances of ethanol withdrawal in rats

Cycloheximide (20 mg/kg body wt, given intraperitoneally at-1 and 3 h after withdrawal of an ethanol-containing liquid diet) prevents the activation of liver tryptophan pyrrolase, the consequent inhibition of synthesis of brain 5-hydroxytryptamine, and the audiogenic seizures observed at 7 h after alcohol withdrawal. We suggest that a rapidly-turning-over protein mediates the alcohol withdrawal syndrome and discuss the possible role of liver tryptophan pyrrolase.

Effects of chronic administration and subsequent withdrawal of ethanol-containing liquid diet on rat liver tryptophan pyrrolase and tryptophan metabolism

An investigation of the effects of chronic administration of ethanol by the liquid diet procedure and its subsequent withdrawal on tryptophan (Trp) metabolism and disposition was performed in rats. Treatment with the control liquid diet caused an enhancement of liver Trp pyrrolase activity and mRNA abundance. These effects are not due to the starvation associated with this feeding procedure, because they occur in rats maintained on the liquid diet ad libitum. Chronic ethanol administration in the liquid diet did not further influence the above increased expression of Trp pyrrolase mRNA but caused inhibition of pyrrolase activity in competition with the effects of the diet. The control liquid diet decreased liver Trp concentration, but exerted no significant effects on other aspects of Trp disposition. The most striking and robust finding was a highly significant elevation in both Trp pyrrolase activity and mRNA expression at 7 h following discontinuation of ethanol availability, at which time there were demonstrable behavioural signs of ethanol withdrawal. The increase in Trp pyrrolase mRNA during alcohol withdrawal may be caused by corticosterone, whose circulating concentration was also increased. The changes in Trp pyrrolase activity during ethanol withdrawal were associated with significant alterations in Trp disposition including decreased brain Trp concentration and 5-hydroxytryptamine synthesis and turnover. These alterations may play a pivotal role in the behavioural manifestations of ethanol withdrawal including the hyperexcitement underlying audiogenic seizures. We suggest that rat Trp pyrrolase gene regulation may be an important biological determinant of the ethanol withdrawal syndrome and requires further study, and that the use of the liquid diet procedure in Trp metabolic studies requires inclusion of adequate controls and special attention to the effects of the liquid diet itself.

Tryptophan metabolism and disposition in relation to alcohol and alcoholism

Tryptophan (Trp) metabolism and disposition in relation to alcohol and alcoholism are briefly reviewed. The changes observed could generally be classified into those: (1) exerted by acute or chronic alcohol administration and/or subsequent withdrawal; (2) already present in the absence of alcohol consumption, such as in naive alcohol-preferring animals or in abstinent alcoholics. In normal rats, acute ethanol administration activates liver Trp pyrrolase and exerts a biphasic effect on brain 5-HT (5-hydroxytryptamine or serotonin) synthesis, whereas chronic ethanol administration and subsequent withdrawal exert opposite effects on 5-HT synthesis mediated by corresponding changes in liver Trp pyrrolase activity. A cerebral 5-HT deficiency has been demonstrated in the alcohol-preferring C57BL mouse strain and in a number of alcohol-preferring rat lines, the mechanism of which is understood only in two models; the C57B1 mouse strain has a higher liver Trp pyrrolase activity and the P rat line from Indiana has a lower density of serotonergic fibres in cerebral cortex. In man, acute ethanol intake lowers circulating [Trp] and its availability to the brain, almost certainly by activating liver Trp pyrrolase. Some evidence exists for possible inhibition of pyrrolase activity in non-abstinent chronic alcoholics. Evidence in recently abstinent alcoholics suggests that Trp availability to the brain may be impaired and that this may be particularly so in patients with positive family history. Exploration of this latter possibility may be important in understanding the biological basis of predisposition to alcoholism.

Decrease in circulating tryptophan availability to the brain after acute ethanol consumption by normal volunteers: implications for alcohol-induced aggressive behaviour and depression

Acute ethanol consumption by fasting male volunteers decreases circulating trytophan (Trp) concentration and availability to the brain as determined by the ratio of (Trp) to the sum of its five competitors ([Trp]/[CAA]ratio). These effects of alcohol are specific to Trp, because levels of the 5 competitors are not increased. The decrease in circulating (Trp) is not associated with altered binding to albumin and may therefore be due to enhancement of hepatic Trp pyrrolase activity. It is suggested that, under these conditions brain serotonin synthesis is likely to be impaired and that, as a consequence, a possible strong depletion of brain serotonin in susceptible individuals may induce aggressive behaviour after alcohol consumption. The possible implications of these findings in the relationship between alcohol and depression are also briefly discussed.

Effects of acute carbamazepine administration on haem metabolism in rat liver

The effects of acute carbamazepine (CBZ) administration on haem metabolism in rat liver were examined in relation to the mechanism by which it exacerbates hepatic porphyrias. In a screening test for drug exacerbation of porphyria developed in this laboratory, CBZ at a very small dose (1.5 mg/kg, p.o.) behaved as an exacerbator, potentiating the loss of haem utilized by tryptophan pyrrolase (TP; tryptophan 2,3-dioxygenase; L-tryptophan-O2 oxido-reductase, decyclizing; EC 1.13.11.11) and the associated induction of activity of the rate-limiting enzyme of haem biosynthesis, 5-aminolaevulinate synthase (5-ALA-S) caused by the experimental porphyrogen 3,5-diethoxycarbonyl-1,4-dihydrocollidine. A larger dose of CBZ (50 mg/kg, i.p.) induced 5-ALA-S activity by 40-100% at 3 hr. This induction was preceded by an increase in the haem saturation of TP, and was abolished when such an increase was prevented by allopurinol. 5-ALA-S induction by CBZ was not associated with decreased turnover of the enzyme, nor with any significant changes in concentration of the major hepatic haemoprotein, cytochrome P450. It is suggested that CBZ may exacerbate the hepatic porphyrias by inducing 5-ALA-S activity secondarily to an increased utilization of haem by TP.

The effects of lofepramine and desmethylimipramine on tryptophan metabolism and disposition in the rat

Acute and chronic administration of lofepramine and its major metabolite desmethylimipramine (DMI) to rats elevates brain tryptophan concentration, thereby enhancing cerebral 5-hydroxytryptamine (5-HT) synthesis, by increasing the availability of circulating tryptophan to the brain, secondarily to inhibition of liver tryptophan pyrrolase (tryptophan 2,3-dioxygenase, L-tryptophan:O2 oxidoreductase, decyclizing; EC 1.13.11.11) activity. The pyrrolase inhibition by lofepramine occurs independently of metabolism to DMI, because it can be demonstrated directly in vitro. Lofepramine also differs from DMI in its action profile on the above and related aspects of tryptophan metabolism and disposition. These results demonstrate that lofepramine influences tryptophan and 5-HT metabolism and disposition independently of its major metabolite DMI, and are discussed briefly in relation to the mechanism of action of antidepressants.

Effects of acute paroxetine administration on tryptophan metabolism and disposition in the rat

1 The effects of acute oral administration of paroxetine on tryptophan metabolism and disposition were examined in the rat. 2 Basal liver tryptophan pyrrolase activity was inhibited by paroxetine in vitro and after oral administration. Maximum inhibition was caused by a 1 mg kg-1 dose. 3 Paroxetine administration also inhibited pyrrolase activity that had previously been enhanced by hormonal induction by cortisol or cofactor activation by haematin. The cortisol induction of the enzyme was, however, not inhibited by pretreatment of rats with paroxetine. 4 Paroxetine increased tryptophan availability to the brain, because of the above pyrrolase-inhibitory mechanism. Cerebral 5-hydroxytryptamine (5-HT) synthesis was accordingly enhanced, though this was apparent only with doses of the drug of up to 1 mg kg-1. With larger doses, decreased 5-HT turnover, probably as a result of 5-HT uptake inhibition, was the more dominant feature. 5 Paroxetine lowered circulating corticosterone concentration, but did not influence those of albumin, non-esterified fatty acids or glucose. 6 It is concluded that, in addition to inhibiting brain 5-HT turnover, paroxetine also, in common with 20 other antidepressants, enhances 5-HT synthesis by increasing brain tryptophan concentration secondarily to inhibition of liver tryptophan pyrrolase activity.

Liver tryptophan pyrrolase. A major determinant of the lower brain 5-hydroxytryptamine concentration in alcohol-preferring C57BL mice

The lower brain 5-hydroxytryptamine concentration in alcohol-preferring C57BL, compared with -non-preferring CBA, mice is caused by a decrease in circulating tryptophan availability to the brain secondarily to a higher liver tryptophan pyrrolase activity associated with a higher circulating corticosterone concentration. Activity or expression of liver tryptophan pyrrolase and/or their induction by glucocorticoids may be important biological determinants of predisposition to alcohol consumption.

Effects of acute ethanol administration on rat liver 5-aminolaevulinate synthase activity

1. Liver 5-aminolaevulinate (ALA) synthase activity of 24 h-starved rats is maximally increased at 4 h after intraperitoneal administration of a 1.6 g/kg body wt. dose of ethanol. Larger doses cause a dose-dependent decrease in the extent of this stimulation, exhibiting a reciprocal relationship with an elevation of hepatic haem concentration, as suggested by the simultaneous increase in the haem saturation of tryptophan pyrrolase. 2. ALA synthase induction by ethanol is abolished if the above increase in pyrrolase saturation with haem is enhanced by theophylline, but is potentiated when the increase in the haem saturation is inhibited by anti-lipolytic agents. 3. ALA synthase induction by ethanol is also inhibited by inhibitors of alcohol dehydrogenase and aldehyde dehydrogenase. Acetaldehyde and acetate are, however, not responsible; they both decrease ALA synthase activity and increase the haem saturation of tryptophan pyrrolase. These latter effects of acetaldehyde are not mediated by acetate. 4. ALA synthase activity is also stimulated by succinate, which, however, also increases the haem saturation of tryptophan pyrrolase. 5. Ethanol does not influence the rate of ALA synthase degradation. 6. It is suggested that ethanol increases rat liver ALA synthase activity as a result of its own metabolism by the alcohol dehydrogenase-dependent pathway by a mechanism not involving decreased degradation of the former enzyme or the participation of the metabolites acetaldehyde and acetate.

Effects of pregnancy on tryptophan metabolism and disposition in the rat

Tryptophan availability in rat serum is increased throughout pregnancy, because of inhibition of liver tryptophan pyrrolase activity during the first 15 days and decreased protein binding thereafter.

Effects of the haem precursor 5-aminolaevulinate on tryptophan metabolism and disposition in the rat

5-Aminolaevulinate administration to rats inhibits cerebral 5-hydroxytryptamine synthesis by decreasing tryptophan availability to the brain secondarily to activation of hepatic tryptophan pyrrolase. The results show that tryptophan metabolism and disposition can be influenced by changes in liver haem concentration, and are discussed briefly in relation to mood disorders in the hepatic porphyrias.

Effects of naloxone and other opiate antagonists on blood-ethanol concentration in acutely-ethanol-intoxicated rats

The effects of naloxone hydrochloride (NAL) and other opiate antagonists on blood-ethanol concentration (BEC) in acutely-ethanol-intoxicated rats were examined. Using a 1 mg/kg body wt. dose of NAL, the maximum decrease in BEC was found to occur at 30 min. At 30 min after administration of various doses of NAL, it was found that BEC was decreased maximally by a 2 mg/kg dose, whereas the first significant decrease was caused by a 10 micrograms/kg dose. BEC was also decreased by naltrexone (1 mg/kg), but not by a 4 mg/kg dose of any of four Mr compounds (Mr 1452, Mr 1453, Mr 2266 and Mr 2267). It is suggested that pharmacokinetic antagonism of acute alcohol intoxication by naloxone and naltrexone is unrelated to the property of opiate antagonism, but may involve the ability of certain such antagonists to interact with hepatic NAD+-dependent oxidative metabolism.

Antagonism of acute alcohol intoxication by naloxone

We have previously shown that proprietary naloxone hydrochloride (Narcan) reverses the disturbance of the redox states of the hepatic NAD(P) couples and causes a simultaneous lowering of blood-ethanol concentration in acutely-ethanol-intoxicated rats. We now confirm these findings by using pure naloxone hydrochloride and demonstrate the inability of the methyl-4-hydroxybenzoate preservative present in the Narcan ampoules to influence the above effects of ethanol.

Role of tyrosine in the acute effects of ethanol on rat brain catecholamine synthesis

Acute ethanol administration exerts multiple effects on rat brain catecholamine synthesis, associated with corresponding changes in cerebral tyrosine concentration. Catecholamine synthesis is enhanced at 1 hr by an increased availability of circulating tyrosine to the brain after inhibition of liver tyrosine aminotransferase activity. Tyrosine hydroxylation in vivo and tyrosine hydroxylase activity measured in vitro are also enhanced at 1 hr. Catecholamine synthesis is inhibited at 2-4 hr when tyrosine availability to the brain is decreased because of an enhancement of liver tyrosine aminotransferase activity. Serum neutral amino acid concentrations are decreased at 5 hr. This is followed 1 hr later by normalization of cerebral catecholamine synthesis. By 8 hr after ethanol administration, the latter becomes enhanced because of increased cerebral uptake of tyrosine. Catecholamine synthesis is inhibited at 12 hr because of enhanced transamination of brain tyrosine. Tyrosine metabolism finally returns to normal at 16 hr after ethanol administration. These results are discussed in relation to previous work with ethanol, and to central and peripheral mechanisms of regulation of brain catecholamine synthesis.

Does naloxone always act as an opiate antagonist?

Evidence for the ability of the opiate antagonist naloxone to block a variety of metabolic effects exerted by morphine and non-opiate drugs is reviewed. Naloxone prevents or reverses the following effects in the rat: (a) the chronic morphine-induced increase in liver [NADPH]; (b) the consequent chronic morphine-induced inhibition of liver tryptophan pyrrolase activity; (c) the resultant chronic morphine-induced enhancement of brain 5-hydroxytryptamine synthesis; (d) the similar effects on liver and brain tryptophan metabolism exerted chronically by other drugs of dependence (ethanol, nicotine and phenobarbitone); (e) the acute ethanol-induced increase in the hepatic [NADH]/[NAD] ratio. Naloxone also (f) inhibits basal and stimulated lipolysis in fed and 24hr-starved rats. This leads to prevention of (g) the consequent increase in the availability of circulating free tryptophan, and (h) the resultant tryptophan-mediated decrease in liver 5-aminolaevulinate synthase activity. The question of how many of these effects involve changes in endogenous opiates or at opiate receptors is not clearly understood at present and thus merits investigation. However, because most of the above effects are explained on biochemical grounds, and in view of evidence from behavioural and pharmacological studies [see (1)], the possibility must be considered that many of the actions of naloxone may be unrelated to its opiate-receptor-antagonistic properties.

Tryptophan and tryptophan pyrrolase in haem regulation. The role of lipolysis and direct displacement of serum-protein-bound tryptophan in the opposite effects of administration of endotoxin, morphine, palmitate, salicylate and theophylline on rat liver 5-aminolaevulinate synthase activity and the haem saturation of tryptophan pyrrolase

1. The increase in the haem saturation of rat liver tryptophan pyrrolase caused by tryptophan administration was previously shown to be associated with a decrease in 5-aminolaevulinate synthase activity. 2. It is now shown that similar reciprocal effects are caused by palmitate and salicylate, both of which increase tryptophan availability to the liver by direct displacement of the serum-protein-bound amino acid. 3. The reciprocal effects on the former two parameters caused by endotoxin and morphine are associated with an increase in liver tryptophan concentration produced by a lipolysis-dependent, non-esterified fatty acid-mediated, displacement of the serum-protein-bound amino acid. 4. All these changes and those caused by another lipolytic agent, theophylline, are prevented by the beta-adrenoceptor-blocking agent propranolol and by the opiate-receptor antagonist naloxone, whose anti-lipolytic nature is demonstrated. 5. High correlation coefficients have been obtained for one or more pairs of the following parameters: serum non-esterified fatty acid concentration, free serum tryptophan concentration, liver tryptophan concentration, liver 5-aminolaevulinate synthase activity, liver holo-(tryptophan pyrrolase) activity and the haem saturation of liver tryptophan pyrrolase. 6. It is suggested that liver tryptophan concentration may play an important role in the regulation of 5-aminolaevulinate synthase synthesis, and that the latter may be subject to control by changes in lipid metabolism and may be influenced by pharmacological agents that affect tryptophan disposition. 7. Preliminary evidence suggests that tryptophan may be bound in the liver and that such a possible binding may control its availability for its hepatic functions.

Tryptophan pyrrolase in haem regulation. The mechanisms of enhancement of rat liver 5-aminolaevulinate synthase activity by starvation and of the glucose effect on induction of the enzyme by 2-allyl-2-isopropylacetamide

1. Rat liver tryptophan pyrrolase activity is enhanced by a hormonal-type mechanism during the first 2 days of starvation and by a substrate-type mechanism during the subsequent 2 days. 5-Aminolaevulinate synthase activity is also enhanced during the first 2 days of starvation, but returns thereafter to values resembling those observed in the fed rat. Treatments that prevent or reversé the enhancement of tryptophan pyrrolase activity in 24-48h-starved rats also abolish that of 5-aminolaevulinate synthase activity. Starvation of guinea pigs, which does not enhance the pyrrolase activity, also fails to alter that of the synthase. It is suggested that the decrease in 5-aminolaevulinate synthase activity in 72-96h-starved rats represents negative-feedback repression of synthesis, possibly involving tryptophan participation, whereas the enhancement observed in 24-48h-starved animals is caused by positive-feedback induction secondarily to increased utilization of the regulatory-haem pool by the newly synthesized apo-(tryptophan pyrrolase). 2. Glucose, fructose and sucrose abolish the 24h-starvation-induced increases in rat liver tryptophan pyrrolase and 5-aminolaevulinate synthase activities. Cortisol reverses the glucose effect on 5-aminolaevulinate synthase activity, presumably by enabling pyrrolase to re-utilize the regulatory-haem pool after induction of synthesis of this latter enzyme. 3. The impaired ability of 2-allyl-2-isopropylacetamide to enhance markedly 5-aminolaevulinate synthase activity in 24h-starved rats treated with glucose is associated with a failure of the porphyrogen to cause loss of tryptophan pyrrolase haem. Cortisol restores the ability of the porphyrogen to destroy tryptophan pyrrolase haem and to enhance markedly 5-aminolaevulinate synthase activity, presumably by enhancing tryptophan pyrrolase synthesis and, thereby, its re-utilization of the regulatory-haem pool. It is tentatively suggested that 2-allyl-2-isopropylacetamide destroys the above pool only after it has become bound to (or utilized by) apo-(tryptophan pyrrolase).