The adherent invasive Escherichia coli (AIEC) pathotype has been associated with the aetiology of Crohn’s disease (CD). Scarce reports have shown the antimicrobial resistance (AMR) profiles of AIEC. Despite antibiotics not being recommended to treat CD, antimicrobial therapy could be useful in stratified patients, such as AIEC carriers. We examined the antimicrobial resistance profiles of AIEC strains to identify which therapies could be effective or confer a risk for such patients. Phenotypic resistance to 30 antimicrobials was tested according to CLSI standards. AIEC (n = 22) and non-pathogenic E. coli (non-AIEC) strains (n = 37) isolated from the gut mucosa of 31 CD patients and 18 controls were studied. De novo genome sequencing was carried out for 39 of the 59 strains, and AMR genes were searched using the DeepARG database in these genomes and 33 additional AIEC publicly available genomes. The strains isolated from CD and controls showed similar phenotypic AMR profiles. The genomic analysis did not reveal an increased prevalence of AMR genes. However, AIEC strains were more frequently resistant to β-lactams than non-AIEC strains (11 AIEC (50%) and 5 non-AIEC (22%) strains were resistant to at least one β-lactam; p < 0.042). Two AIEC strains were resistant to expanded-spectrum cephalosporins. One strain carried a plasmid-mediated AmpC β-lactamase (CMY-69), and the other presented mutations in the promotor of the intrinsic chromosomal AmpC related to the hyperproduction of this enzyme. The rest of the strains were resistant to β-lactams not including expanded-spectrum cephalosporins. The majority carried TEM-related β-lactamases. Genomic analysis including external AIEC revealed that the gene sul1 encoding for sulphonamide resistance was more frequent in AIEC strains than non-AIEC strains (34.6% vs. 9.5%, p = 0.030). AMR in AIEC is a matter of concern regarding the putative implication of the pathotype in CD. The high proportion of AIEC resistant to β-lactams warrants caution about the risk there may be in the use of these antimicrobials in AIEC-colonized CD patients.

The mineralocorticoid receptor (MR) is a ligand-activated transcription factor that transduces the effects of aldosterone and glucocorticoids in a tissue-and cell type-specific ways. Differential regulation of MR by post-translational modifications (PTMs) has been proposed to play a key role in modulating its function. In addition, modifications of other proteins that physically or functionally interact with MR add an additional layer of regulation to aldosterone or glucocorticoid signaling. In this chapter, we will summarize the main post-translational modifications of MR described so far, discussing their possible implications in the physiological and pathological roles of the receptor. We will also discuss post-translational modulation of other proteins impacting MR function such as heat shock protein 90 or 11ß-hydroxysteroid dehydrogenase type 2.

Liver cirrhosis is associated to circulatory abnormalities leading to hypovolemia and stimulation of the renin-angiotensin-aldosterone system (RAAS). Advanced stages of the disease cause renal failure, impairing K+ and Na+ homeostasis. It has been proposed that the distal colon undergoes functional remodeling during renal failure, in particular by aldosterone-driven increased K+ excretion. In this study, we compared the transcriptional response of aldosterone target genes in the rat distal colon under two models of increased circulating aldosterone (one with concomitant RAAS activation) and in a model of secondary hyperaldosteronism induced by cirrhosis. The expression of a subset of these genes was also tested in distal colon biopsies from control subjects or cirrhotic patients with varying levels of disease progression and treated or not with mineralocorticoid receptor inhibitor spironolactone. We examined known aldosterone-regulated transcripts involved in corticosteroid signaling and transepithelial ion transport. In addition, we included aldosterone-regulated genes related to cell proliferation. Our comparison revealed multiple aldosterone target genes upregulated in the rat distal colon during decompensated cirrhosis. Epithelial Na+channel b and g subunit expression correlated positively with plasma aldosterone concentration and negatively with glomerular filtration rate. Cirrhotic patients showed increased expression of 11bHSD2, which was reverted by spironolactone treatment, suggesting a sensitization of the distal colon to aldosterone action. We conclude that cirrhosis progression towards a decompensated state with hypovolemia induces remodeling of distal colon ion transporter expression to match a decaying kidney function, supporting a role for aldosterone in the process.

The mineralocorticoid receptor (MR) belongs to the steroid receptor subfamily of nuclear receptors. MR is a transcription factor key in regulating blood pressure and mineral homeostasis. In addition, it plays an important role in a broad range of biological and pathological conditions, greatly expanding its interest as a pharmacological target. Non-steroidal MR antagonists (MRAs) are of particular interest to avoid side effects and achieve tissue-specific modulation of the receptor. The 1,4-dihydropyridine (1,4-DHP) ring has been identified as an appropriate scaffold to develop non-steroidal MRAs. We report the identification of a novel series of 1,4-DHP that has been guided by structure-based drug design, focusing on the less explored DHP position 2. Interestingly, substituents at this position might interfere with MR helix H12 disposition, which is essential for the recruitment of co-regulators. Several of the newly synthesized 1,4-DHPs show interesting properties as MRAs and have a good selectivity profile. These 1,4-DHPs promote MR nuclear translocation with less efficiency than the natural agonist aldosterone, which explains, at least in part, its antagonist character. Molecular dynamic studies are suggestive of several derivatives interfering with the disposition of H12 in the agonist-associated conformation, and thus, they might stabilize an MR conformation unable to recruit co-activators.

Hepatic cirrhosis is associated to circulatory abnormalities. A combination of vasodilation, lower plasmatic protein content and splanchnic venous stagnation leads to hypovolemia, which in turn stimulates the renin‐angiotensin‐aldosterone system (RAAS). Advanced stages of the disease cause renal failure and subsequent impaired K+ homeostasis. It has been proposed that the distal colon undergoes functional remodeling during renal failure, in particular by aldosterone‐driven increased K+ excretion. In this study, we compared the transcriptional response of aldosterone target genes in the rat distal colon under two models of increased circulating aldosterone, one with concomitant RAAS activation, and in a model of hepatic cirrhosis. We examined known aldosterone‐regulated transcripts involved in corticosteroid signaling and transepithelial ion transport. In addition, we included new aldosterone‐regulated genes identified via whole transcriptome analysis. Our comparison revealed that multiple aldosterone‐target genes are upregulated during cirrhosis in the rat distal colon. This upregulation is more prominent in animals showing decompensated cirrhosis. Epithelial Na+channel (ENaC) β and γ subunit expression correlated positively with plasma aldosterone concentration and negatively with glomerular filtration rate. Altogether, our results demonstrate cirrhosis‐induced ion transporter subunit expression remodeling, a change that correlated well with the severity of the disease and suggested a role for aldosterone in the process. The expression of a subset of these genes was then tested in distal colon biopsies obtained from patients showing decompensated cirrhosis and treated or not with mineralocorticoid receptor inhibitor spironolactone. Preliminary results show decreased expression of ENaC subunits and channel regulator K‐ras in patients treated with spironolactone. We conclude that cirrhosis progression towards a decompensated state with hypovolemia induces remodeling of distal colon ion transporter expression to match a decaying kidney function.