Distinctive gut microbiomes of ankylosing spondylitis and inflammatory bowel disease patients suggest differing roles in pathogenesis and correlate with disease activity

BACKGROUND

Multiple studies have confirmed dysbiosis in ankylosing spondylitis (AS) and inflammatory bowel disease (IBD); however, due to methodological differences across studies, it has not been possible to determine if these diseases have similar or different gut microbiomes.

RESULTS

In this study, faecal and intestinal biopsies were obtained from 33 Australian AS patients (including 5 with concomitant IBD, 'AS-IBD'), 59 IBD patients and 105 healthy controls. Stool samples were also obtained from 16 Italian AS patients and 136 Swedish AS patients. Focusing on the Australian cohort, AS, AS-IBD and IBD patients differed from one another and from healthy controls in both alpha and beta diversity. AS patients with and without clinical IBD could be distinguished from one another with moderate accuracy using stool microbiome (AUC=0.754). Stool microbiome also accurately distinguished IBD patients from healthy controls (AUC=0.757). Microbiome composition was correlated with disease activity measured by BASDAI and faecal calprotectin (FCP) levels. Enrichment of potentially pathogenic Streptococcus was noted in AS, AS-IBD and IBD patients. Furthermore, enrichment of another potentially pathogenic genus, Haemophilus, was observed in AS, AS-IBD, IBD, AS patients with increased BASDAI, and IBD patients with faecal calprotectin >100 μg/mg. Apart from these genera, no other taxa were shared between AS and IBD patients.

CONCLUSIONS

In conclusion, the distinct gut microbiome of AS and AS-IBD patients compared to IBD patients and healthy controls is consistent with immunological and genetic evidence suggesting that the gut plays a different role in driving AS compared with IBD. However, enrichment of two potentially pathogenic genera in both diseases suggests that the presence of a shared/common microbial trigger of disease cannot be discounted.

Nuclear thymidylate synthase expression, p53 expression and 5FU response in colorectal carcinoma

Thymidylate synthase (TS) is a key enzyme in DNA synthesis and is inhibited by metabolites of the chemotherapeutic agent 5-fluorouracil (5FU). Nuclear expression of TS in human tissue in vivo has not been characterised and its clinicopathological correlates in malignancy are unknown. 52 cases of primary colorectal carcinoma (CRC) and 24 cases of matched metastatic carcinoma were studied immunohistochemically using the monoclonal antibody TS106. The degree of nuclear TS immunostaining correlated closely with levels of TS mRNA expression amongst 10 CRCs studied. Strong nuclear immunostaining was seen in normal basal crypt colonocytes and germinal centre cells, and in a varying proportion of adenocarcinoma cells. Amongst the primary carcinomas, higher TS nuclear expression was associated with prominent extracellular mucin production and right-sided location. Higher TS nuclear expression also showed a significant association with poorer response to protracted venous infusional 5FU therapy. There was no clear association between TS nuclear expression and Ki67 or p53 expression assessed immunohistochemically. There was a strong positive correlation between TS nuclear expression in primary and metastatic CRC but the latter generally showed higher expression than matched primary tumour tissue. These findings confirm the nuclear expression of TS protein in human cells in vivo and provide new insight into how such expression may relate to the behaviour of CRCs.

Distribution of glucocorticoid and mineralocorticoid receptors and 11beta-hydroxysteroid dehydrogenases in human and rat ocular tissues

PURPOSE

The administration of glucocorticoids as topical or systemic medications may lead to the development of ocular hypertension through the induction of morphologic and biochemical changes in the trabecular meshwork leading to a reduction in the facility of aqueous outflow. Glucocorticoids exert their physiological effects by binding to and activating glucocorticoid and mineralocorticoid receptors. The activity of glucocorticoids is critically regulated at a prereceptor level by the two isozymes of 11beta-hydroxysteroid dehydrogenase. The purpose of this study was to determine the distribution of glucocorticoid target receptors and the isozymes of 11beta-hydroxysteroid dehydrogenase (11 beta-HSD) that regulate the activity of glucocorticoids at a prereceptor level in human and rat ocular tissues.

METHODS

Horizontal sections of normal adult human and rat eyes were cut and hybridized with 35S-labeled cRNA probes specific for the glucocorticoid receptor, mineralocorticoid receptor, and 11beta-HSD types 1 and 2 using in situ hybridization. Immunohistochemical analysis of glucocorticoid and mineralocorticoid receptors using monoclonal antibodies was carried out on rat eye tissue sections. Whole rat eyes were homogenized and the activity of 11beta-HSD types 1 and 2 in the eye assessed as the percentage conversion of tritiated corticosterone to tritiated 11-dehydrocortico-sterone when corticosterone was added to the homogenate.

RESULTS

In the rat ocular tissues mRNAs encoding glucocorticoid receptor, mineralocorticoid receptor, and 11beta-HSD types 1 and 2 were detected in nonpigmented ciliary epithelium, trabecular meshwork, corneal epithelium and endothelium, and anterior lens epithelium. Immunohistochemistry confirmed the presence of glucocorticoid and mineralocorticoid receptors at these sites. Activity of both isozymes of 11beta-HSD was demonstrated in homogenized rat eyes (percentage conversion of tritiated corticosterone to 11-dehydrocorticosterone; mean +/- SD, 11beta-HSD 1 = 15% +/- 5.3%, 11beta-HSD 2 = 7.9% +/- 2.8%). In both human and rat eyes, expression of mRNAs encoding glucocorticoid receptor and 11beta-HSD type 1 was high in the trabecular meshwork and lens epithelium, whereas expression of mRNAs encoding the mineralocorticoid receptor and 11beta-HSD type 2 was high in nonpigmented ciliary epithelium and corneal epithelium and endothelium.

CONCLUSIONS

Glucocorticoid target receptors and the enzymes regulating glucocorticoid activity at these receptors are present in mammalian ocular tissues, which regulate aqueous humor formation and outflow. Alteration in the number or affinity of receptors or in the activity of regulatory enzymes may alter the susceptibility of certain individuals to the effects of glucocorticoids on intraocular pressure.

StAR protein is expressed in both medulla and cortex of the bovine and rat adrenal gland

We have employed polyclonal antibodies to a peptide sequence of bovine steroidogenic acute regulatory (StAR) protein and human placental 3beta-hydroxysteroid dehydrogenase (3beta-HSD) to determine the localisation and distribution of these proteins in rat and bovine adrenal glands. Immunohistochemical staining demonstrated the presence of StAR protein in the zona glomerulosa (ZG), zona fasciculata (ZF), zona reticularis (ZR) and in the medulla of both species. For 3beta-HSD, immunostaining was observed in the ZG, ZF and ZR of the rat adrenal and was absent in the medulla. Immunoblotting experiments showed intense bands for StAR protein (30 kDa, 37 kDa) in the mitochondria of bovine ZG, ZF and medulla and a less intense band (30 kDa) in the microsomes. In rat ZG and ZF/R mitochondria only the 30 kDa protein was present. For 3beta-HSD, an intense band (42 kDa) was found in microsomes and mitochondria of rat and bovine ZG and ZFR. A very faint signal for 3beta-HSD was seen in adrenal medulla. In conclusion, StAR (or a closely related) protein is present throughout the adrenal gland in rat and bovine species in contrast to 3beta-HSD which is confined to the steroidogenic zones. The possible function of StAR protein in the adrenal medulla merits investigation.

Nitric oxide and gall-bladder motor function

BACKGROUND

The L-arginine: nitric oxide (NO) pathway has been shown to be important in the regulation of intestinal motility and NO may be the mediator for nonadrenergic noncholinergic (NANC) neurotransmission.

AIM

To determine the role of the L-arginine: NO pathway in gall-bladder motor function.

METHODS

Strips of fresh bovine and human gall-bladders were stimulated with cholecystokinin (CCK). The effects of glyceryl trinitrate (GTN), sodium nitroprusside and Kreb's solution upon CCK-stimulated muscle contraction were examined. The effect of the NO synthase inhibitor, L-NG-monomethyl-arginine (L-NMMA) upon basal muscle tone was also examined. Ten human gall-bladders were immunohistochemically stained for nitric oxide synthase (NOS) and product 9.5 to identify neurones. Postprandial gall-bladder emptying was measured on separate occasions in six healthy volunteers during systemic intravenous infusion of normal saline; glyceryl trinitrate; sodium nitroprusside (SNP), hydralazine and L-NMMA.

RESULTS

In the in vitro study, GTN and SNP significantly reduced the tension of CCK-stimulated muscle contraction whilst Kreb's solution had no effect. L-NMMA increased tonic and phasic muscle contractions. Immunohistochemical staining for NOS was consistently absent in human gall-bladders. In the in vivo study, both GTN and SNP caused significant impairment of gall-bladder emptying; the ejection fraction was only 50% at the end of the study period involving these infusates, this contrasted with ejection fractions in excess of 80% during infusions with hydralazine, saline and L-NMMA.

CONCLUSION

Pharmacological doses of NO donors impair postprandial gall-bladder emptying in vivo and relax gall-bladder smooth muscle in vitro. However, negative immunohistochemical staining suggest NOS is unlikely to be the neurotransmitter for NANC innervation regulating gall-bladder motility.

The role of L-aromatic amino acid decarboxylase in serotonin-stimulated aldosterone secretion in response to salt intake

In this study we tested a new hypothesis namely that serotonin (5-hydroxytryptamine, 5-HT) could be synthesised within the zona glomerulosa of the rat adrenal gland from exogenous 5-hydroxytryptophan (5-HTP) by the enzyme L-aromatic amino acid decarboxylase (L-AAAD). A specific monoclonal antibody against L-AAAD showed that the enzyme was present predominantly in the adrenal medulla but also in the zona glomerulosa and zona fasciculata. Wistar rats, maintained on a normal (NS), low (LS) or high (HS) salt diet for one week, were sacrificed by decapitation, blood samples taken and the adrenal glands removed. Plasma aldosterone concentrations were significantly higher in the LS diet group (2.91 +/- 0.35 nM) and significantly lower in the HS diet group (0.261 +/- 0.55 nM) compared with the NS diet group (1.025 +/- 0.133 nM) (p < 0.001). Capsules from the LS diet group synthesised significantly higher maximal levels of 5-HT (2615.463 +/- 480.88 nM/mg protein) than capsules from the NS (1219.117 +/- 150.259 nM/mg protein) and the HS (968.477 +/- 214.485 nM/mg protein) salt diet groups (p < 0.05). Maximal aldosterone secretion in adrenal capsules obtained from rats on the LS diet (73.428 +/- 4.053 nM/mg protein) was significantly higher than in those obtained from rats on the NS diet (41.658 +/- 1.87 nM/mg protein) (p < 0.05). Maximal aldosterone secretion in adrenal capsules from the HS diet group (30.624 +/- 2.114 nM/mg protein) was significantly lower than in the capsules from both the LS and NS groups (p < 0.05). Carbidopa (10(-4) M), a specific inhibitor of L-AAAD, markedly attenuated the secretion of aldosterone when adrenal capsules from all three salt diet groups were incubated with 10(-4) M 5-HTP (p < 0.05), but had no significant effect on basal aldosterone secretion. These results clearly demonstrate that L-AAAD is not only present in the medulla, but also in the zona glomerulosa and zona fasciculata of the rat adrenal gland. In addition, 5-HT can be synthesised in the zona glomerulosa/capsular region of the rat adrenal gland and both its biosynthesis and its ability to stimulate aldosterone secretion is increased by sodium depletion and attenuated by sodium loading. This raises the interesting possibility that L-AAAD could play a role in the regulation of aldosterone secretion during sodium deficiency in the rat by converting circulating 5-HTP (which is present in blood at concentrations exceeding 1 micromolar) into 5-HT within the adrenal cortex.

Cloning and production of antisera to human placental 11 beta-hydroxysteroid dehydrogenase type 2

By inactivating potent glucocorticoid hormones (cortisol and corticosterone), 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2) plays an important role in the placenta by controlling fetal exposure to maternal glucocorticoids, and in aldosterone target tissues by controlling ligand access to co-localized glucocorticoid and mineralocorticoid receptors. Amino acid sequence from homogeneous human placental 11 beta-HSD2 was used to isolate a 1897 bp cDNA encoding this enzyme (predicted M(r) 44126; predicted pI 9.9). Transfection into mammalian (CHO) cells produces 11 beta-HSD2 activity which is NAD(+)-dependent, is without reductase activity, avidly metabolizes glucocorticoids (Km values for corticosterone, cortisol and dexamethasone of 12.4 +/- 1.5, 43.9 +/- 8.5 and 119 +/- 15 nM respectively) and is inhibited by glycyrrhetinic acid and carbenoxolone (IC50 values 10-20 nM). Rabbit antisera recognizing 11 beta-HSD2 have been raised to an 11 beta-HSD2-(370--383)-peptide-carrier conjugate. Recombinant 11 beta-HSD2, like native human placental 11 beta-HSD2, is detectable with affinity labelling and anti-11 beta-HSD2 antisera, and appears to require little post-translational processing for activity. 11 beta-HSD2 mRNA (approximately 1.9 kb transcript) is expressed in placenta, aldosterone target tissues (kidney, parotid, colon and skin) and pancreas. In situ hybridization and immunohistochemistry localize abundant 11 beta-HSD2 expression to the distal nephron in human adult kidney and to the trophoblast in the placenta. 11 beta-HSD2 transcripts are expressed in fetal kidney (but not lung, liver or brain) at 21-26 weeks, suggesting that an 11 beta-HSD2 distribution resembling that in the adult is established by this stage in human development.

Overexpression of the p53 protein and allele loss at 17p13 in ovarian carcinoma

Mouse monoclonal antibodies PAb 240 and PAb 1801 which specifically immunoprecipitate p53 protein, were used to examine 27 fresh ovarian tumours (16 serous adenocarcinomas, six endometrioid carcinomas, one mucinous adenocarcinoma, one mucinous borderline tumour and three benign adenomas). Eleven out of 16 (69%) serous adenocarcinomas and one endometrioid tumour showed positive staining with one or both antibodies and none of the mucinous or benign tumours stained with either antibody. DNA from tumour and peripheral blood leukocytes was used to identify allelic deletions on chromosome 17p in tumours. 11/12 positively staining tumours showed less of heterozygosity (LOH) on 17p at the nearest informative locus to the p53 gene. In this series of ovarian tumours, LOH on 17p correlates closely with the aberrant expression of the p53 protein in a high proportion of advanced stage serous adenocarcinomas. This observation suggests that the p53 tumour suppressor gene is involved in the evolution of epithelial ovarian cancer (EOC) and may have prognostic significance.

Potentiation of hydrocortisone activity in skin by glycyrrhetinic acid

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD), which catalyses the conversion of cortisol to the inactive steroid cortisone in man (and corticosterone to 11-dehydrocorticosterone in rodents), was demonstrated by immunohistochemistry in skin biopsy samples from healthy volunteers and from patients with psoriasis and eczema. In-vitro studies confirmed the presence of the enzyme in skin from nude mice and showed that it is inhibited by glycyrrhetinic acid, the major active component of liquorice. By means of the skin vasoconstrictor assay, glycyrrhetinic acid was shown to potentiate the action of hydrocortisone. This work suggests a novel means of targeting glucocorticoid therapy.

Localisation of 11 beta-hydroxysteroid dehydrogenase--tissue specific protector of the mineralocorticoid receptor

In vitro the mineralocorticoid receptor is non-specific and does not distinguish between aldosterone and cortisol. In vivo certain tissues with this receptor are aldosterone selective (eg, kidney and parotid) whereas others with the same receptor are not (eg, hippocampus and heart). Experiments in rats showed that 11 beta-hydroxysteroid dehydrogenase (which converts cortisol to cortisone in man and corticosterone to 11-dehydrocorticosterone in the rat) was much more highly concentrated in aldosterone-selective tissues than in non-selective tissues. The localisation in the selective tissues was such that the enzyme could act as a paracrine or possibly an autocrine mechanism protecting the receptor from exposure to corticosterone. Autoradiographic studies showed that protection is lost when the enzyme is inhibited; 3H-corticosterone and 3H-aldosterone were bound to similar sites. These findings seem to explain why sodium retention, hypokalaemia, and hypertension develop in subjects with congenital deficiency of 11 beta-OHSD and those in whom the enzyme has been inhibited by liquorice.