Safety and effectiveness of direct-acting antiviral drugs in the treatment of hepatitis C in patients with inflammatory bowel disease

BACKGROUND AND AIMS

Hepatitis C virus (HCV) management in Inflammatory Bowel Disease (IBD) is uncertain. The ECCO guidelines 2021 recommended HCV treatment but warn about the risk of IBD reactivation. We aimed to evaluate 1) the effectiveness and safety of direct-acting antivirals (DAAs) in IBD; 2) the interaction of DAAs with IBD drugs.

METHODS

Multicentre study of IBD patients and HCV treated with DAAs. Variables related to liver diseases and IBD, as well as adverse events (AEs) and drug interactions, were recorded. McNemar's test was used to assess differences in the proportion of active IBD during the study period.

RESULTS

We included 79 patients with IBD and HCV treated with DAAs from 25,998 IBD patients of the ENEIDA registry. Thirty-one (39.2 %) received immunomodulators/biologics. There were no significant differences in the percentage of active IBD at the beginning (n = 11, 13.9 %) or at the 12-week follow-up after DAAs (n = 15, 19 %) (p = 0.424). Sustained viral response occurred in 96.2 % (n = 76). A total of 8 (10.1 %) AEs occurred and these were unrelated to activity, type of IBD, liver fibrosis, immunosuppressants/biologics, and DAAs.

CONCLUSIONS

We demonstrate a high efficacy and safety of DAAs in patients with IBD and HCV irrespective of activity and treatment of IBD.

Endoscopic treatment (endoscopic balloon dilation/self-expandable metal stent) vs surgical resection for the treatment of de novo stenosis in Crohn's disease (ENDOCIR study): an open-label, multicentre, randomized trial

BACKGROUND

Stenosis is one of the most common complications in patients with Crohn's disease (CD). Endoscopic balloon dilation (EBD) is the treatment of choice for a short stenosis adjacent to the anastomosis from previous surgery. Self-expandable metal stents (SEMS) may be a suitable treatment option for longer stenoses. To date, however, there is no scientific evidence as to whether endoscopic (EBD/SEMS) or surgical treatment is the best approach for de novo or primary stenoses that are less than 10 cm in length.

METHODS/DESIGN

Exploratory study as "proof-of-concept", multicentre, open-label, randomized trial of the treatment of de novo stenosis in the CD; endoscopic treatment (EBD/SEMS) vs surgical resection (SR). The type of endoscopic treatment will initially be with EDB; if a therapeutic failure occurs, then a SEMS will be placed. We estimate 2 years of recruitment and 1 year of follow-up for the assessment of quality of life, costs, complications, and clinical recurrence. After the end of the study, patients will be followed up for 3 years to re-evaluate the variables over the long term. Forty patients with de novo stenosis in CD will be recruited from 15 hospitals in Spain and will be randomly assigned to the endoscopic or surgical treatment groups. The primary aim will be the evaluation of the patient quality of life at 1 year follow-up (% of patients with an increase of 30 points in the 32-item Inflammatory Bowel Disease Questionnaire (IBDQ-32). The secondary aim will be evaluation of the clinical recurrence rate, complications, and costs of both treatments at 1-year follow-up.

DISCUSSION

The ENDOCIR trial has been designed to determine whether an endoscopic or surgical approach is therapeutically superior in the treatment of de novo stenosis in CD.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04330846. Registered on 1 April 1 2020. https://clinicaltrials.gov/ct2/home.

Immigrant IBD Patients in Spain Are Younger, Have More Extraintestinal Manifestations and Use More Biologics Than Native Patients

Background

Previous studies comparing immigrant ethnic groups and native patients with IBD have yielded clinical and phenotypic differences. To date, no study has focused on the immigrant IBD population in Spain.

Methods

Prospective, observational, multicenter study comparing cohorts of IBD patients from ENEIDA-registry who were born outside Spain with a cohort of native patients.

Results

We included 13,524 patients (1,864 immigrant and 11,660 native). The immigrants were younger (45 ± 12 vs. 54 ± 16 years, p < 0.001), had been diagnosed younger (31 ± 12 vs. 36 ± 15 years, p < 0.001), and had a shorter disease duration (14 ± 7 vs. 18 ± 8 years, p < 0.001) than native patients. Family history of IBD (9 vs. 14%, p < 0.001) and smoking (30 vs. 40%, p < 0.001) were more frequent among native patients. The most prevalent ethnic groups among immigrants were Caucasian (41.5%), followed by Latin American (30.8%), Arab (18.3%), and Asian (6.7%). Extraintestinal manifestations, mainly musculoskeletal affections, were more frequent in immigrants (19 vs. 11%, p < 0.001). Use of biologics, mainly anti-TNF, was greater in immigrants (36 vs. 29%, p < 0.001). The risk of having extraintestinal manifestations [OR: 2.23 (1.92–2.58, p < 0.001)] and using biologics [OR: 1.13 (1.0–1.26, p = 0.042)] was independently associated with immigrant status in the multivariate analyses.

Conclusions

Compared with native-born patients, first-generation-immigrant IBD patients in Spain were younger at disease onset and showed an increased risk of having extraintestinal manifestations and using biologics. Our study suggests a featured phenotype of immigrant IBD patients in Spain, and constitutes a new landmark in the epidemiological characterization of immigrant IBD populations in Southern Europe.

Clinical features, therapeutic requirements and evolution of patients with Crohn's disease and upper gastrointestinal involvement (CROHNEX study)

BACKGROUND

Crohn's disease (CD) with upper gastrointestinal involvement (UGI) may have a more aggressive and refractory course. However, evidence on this phenotype of patients is scarce.

AIMS

To identify the clinical characteristics, therapeutic requirements and complications associated with UGI in CD METHODS: Nationwide study of cases (UGI, UGI plus ileal/ileocolonic involvement) paired with controls (ileal/ileocolonic involvement) from the ENEIDA registry. Cases were matched to 2 controls by year of diagnosis ± 2.5 years. Patients with exclusive/predominant colonic location or complex perianal fistula were excluded.

RESULTS

Of 24 738 patients with CD in the ENEIDA registry, we identified 4058 with UGI (16% of the total CD cohort). Finally, 854 cases and 1708 controls were included. Cases were independently associated to extensive involvement (OR 2.7 [2.2-3.3], P < 0.0001), strictures [OR 1.8 (1.5-2.2), P < 0.0001], chronic iron deficiency anaemia [OR 2.2 (1.3-3.2), P < 0.001] and use of second-line biologics [OR 1.7 (1.1-2.6), P = 0.021]. The median stricture-free time was 14 years (95% CI, 12-16) for cases vs 21 years (95% CI, 19-23) for controls (P < 0.0001). Cases with isolated UGI compared to UGI plus ileal/ileocolonic more frequently had localised disease [OR 0.5(0.3-0.8), P = 0.003] and underwent more endoscopic stricture dilations [OR 2.7(1.3-5.4), P = 0.006].

CONCLUSIONS

The largest cohort of patients with CD and UGI provides information on the natural history of this particular phenotype. Increased awareness of the clinical picture and therapeutic requirements of these patients could lead to earlier diagnosis and treatment of upper gastrointestinal lesions, preventing the structural damage frequently seen in these patients at diagnosis and during follow-up.

Development and validation of the QUECOMIICAT questionnaire: a tool to assess disease-related knowledge in patients with inflammatory bowel disease

INTRODUCTION

adequate knowledge of inflammatory bowel disease (IBD) is essential for a successful patient-centered management of IBD.

OBJECTIVE

due to the scarcity of up-to-date tools for measuring IBD literacy, this single-center, prospective study aimed to develop and validate a new questionnaire to assess IBD-related knowledge.

MATERIAL AND METHODS

the study included patients followed up at the Crohn-Colitis Care Unit (UACC) at the Hospital Vall d'Hebron (Barcelona, Spain). Patients admitted to the UACC for the first time were subsequently enrolled into a standard IBD educational program. A pilot questionnaire was developed and validated in 92 IBD patients by determining the internal consistency reliability (Cronbach's α test), feasibility, construct validity (correlation with the Crohn's and Colitis Knowledge [CCKNOW] questionnaire and a knowledge visual analog scale [VAS]) and sensitivity (score change before and after a standard IBD educational program). The questionnaire, named "Qüestionari Coneixements Malaltia Inflamatòria Intestinal Catalunya" (IBD-knowledge questionnaire Catalonia) (QUECOMIICAT) was written in Spanish and had 25 items addressing six dimensions: general concepts, clinic, treatment, surgery, habits and social context.

RESULTS

the median (interquartile range) completion time was 15 (10-20) minutes and the floor and ceiling effects were 1.1% and 2.1%, respectively. The Cronbach's α coefficient was α = 0.75. QUECOMIICAT significantly correlated with the VAS (rho = 0.34, p < 0.01) and CCKNOW questionnaires (rho = 0.74, p < 0.01). Patient knowledge significantly increased 24 hours after attending a standard IBD educational program and remained statistically significant one month later (Pearson's test-retest correlation coefficient r = 0.81, p < 0.001).

CONCLUSION

in conclusion, the QUECOMIICAT questionnaire is a new up-to-date tool to assess IBD-related knowledge with good feasibility and validation results for use in the routine clinical practice.

Short and long-term effectiveness and safety of vedolizumab in inflammatory bowel disease: results from the ENEIDA registry

BACKGROUND

Effectiveness of vedolizumab in real world clinical practice is unknown.

AIM

To evaluate the short and long-term effectiveness of vedolizumab in patients with inflammatory bowel disease (IBD).

METHODS

Patients who received at least 1 induction dose of vedolizumab were included. Effectiveness was defined based on Harvey-Bradshaw index (HBI) in Crohn's disease (CD) and Partial Mayo Score (PMS) in ulcerative colitis (UC). Short-term response was assessed at week 14. Variables associated with short-term remission were identified by logistic regression analysis. The Kaplan-Meier method was used to evaluate the long-term durability of vedolizumab treatment. Cox model was used to identify factors associated with discontinuation of treatment and loss of response.

RESULTS

521 patients were included (median follow-up 10 months [interquartile range 5-18 months]). At week 14, 46.8% had remission and 15.7% clinical response. CD (vs UC), previous surgery, higher CRP concentration and disease severity at baseline were significantly associated with impaired response. The rate of vedolizumab discontinuation was 37% per patient-year of follow-up (27.6% in UC and 45.3% in CD, P < 0.01). CD (vs UC), anaemia at baseline, steroids during induction and CRP concentration were associated with lower durability of treatment. Seven per cent of patients developed adverse events, infections being the most frequent.

CONCLUSIONS

Over 60% of IBD patients respond to vedolizumab. Many patients discontinue treatment over time. CD and disease burden impair both short- and long-term response. Vedolizumab seems to be safe in clinical practice.

[Inappropriateness rate for colonoscopy indications in an open access unit]

INTRODUCTION AND OBJECTIVE

The suitability of indications for colonoscopy is important to optimize the available resources. The aim of this study was to assess the appropriateness of colonoscopy indications in an open access endoscopy unit using the EPAGE II criteria.

METHODS

Colonoscopies performed between October 1 and November 30, 2011 were retrospectively included. The appropriateness of the colonoscopy was established according to the EPAGE II criteria. Demographics, medical applicants, indications and relevant findings from these examinations were recorded.

RESULTS

We included 440 colonoscopies (60.8 ± 016.3 years, 54% women). The indication was appropriate in 75.4% (CI, 71-79.3%), uncertain in 13.1% (CI, 10.2-16.6%) and inappropriate in 11.4% (CI, 8.7-14.8%). In the univariate analysis, the relevant findings in the colonoscopy were associated with age, sex, colonoscopy indications and EPAGE II. In the logistic regression analysis, factors independently associated with the presence of relevant findings were age (≥ 50 years) (OR, 1.84), male sex (OR, 2.7) and two indications, inflammatory bowel disease and post-polypectomy surveillance (P < .03). The diagnostic yield of EPAGE II criteria was 37.3% for appropriate colonoscopies and 28.3% for inappropriate colonoscopies (P = .09).

CONCLUSIONS

The rate of unnecessary colonoscopy is high, especially in young patients (<50 years) and some colonoscopy indications. Age (≥ 50 years) and male sex are independently associated with the presence of relevant findings in colonoscopy. The diagnostic yield of EPAGE II criteria does not differ between appropriate and inappropriate examinations.

Efficacy of anti-TNF therapies in refractory severe microscopic colitis

BACKGROUND

Refractory microscopic colitis is a rare condition with an unknown rate of occurrence. The efficacy of anti-tumor necrosis factor (TNF) therapy for microscopic colitis has never been reported. Aims 1) To report the frequency of refractory microscopic colitis in the database of the participant hospitals. 2) To describe the therapeutic response to anti-TNF therapy among the refractory cases.

METHODS

Patients with a histological diagnosis of collagenous colitis and lymphocytic colitis were identified through the Department of Pathology database and the IBD practice database. Patients refractory to medical treatment and with severe symptoms were offered anti-TNF therapy.

RESULTS

Five of 372 MC patients (1.3%; 95% CI, 0.6 to 3.1) presented with severe symptoms refractory to standard medical therapies. One patient was denied therapy from her insurance carrier. The other 4 received infliximab therapy. The response was excellent after one dose experiencing a 60-90% decrease in bowel movements. Three patients were switched to adalimumab (2 allergic reactions and 1 early loss of response to infliximab). Long-term clinical remission (more than 1 year) was achieved in three cases (2 with adalimumab and 1 with infliximab). One patient on adalimumab had an early loss of response and was referred for colectomy.

CONCLUSIONS

Microscopic colitis with severe symptoms refractory to standard medical therapy including immunosuppressives is uncommon. In this setting, anti-TNF therapies may be a good option to avoid colectomy.

Identification of a novel member of the T1R family of putative taste receptors

In the gustatory system, the recognition of sugars, amino acids and bitter-tasting compounds is the function of specialized G protein-coupled receptors. Recently, two members of novel subfamily of G protein-coupled receptors were proposed to function as taste receptors based on their specific expression in taste receptor cells. Here, we report the identification of a third member, T1R3, of this family of receptors. T1R3 maps near the telomere of mouse chromosome 4 rendering it a candidate for the Sac locus, a primary determinant of sweet preference in mice. Consistent with its candidacy for the Sac locus, T1R3 displays taste receptor cell-specific expression. In addition, taster and non-taster strains of mouse harbor different alleles of T1R3.

An aspartate residue at the extracellular boundary of TMII and an arginine residue in TMVII of the gastrin-releasing peptide receptor interact to facilitate heterotrimeric G protein coupling

The mammalian bombesin receptor subfamily of G protein-coupled receptors currently consists of the gastrin-releasing peptide receptor (GRP-R), neuromedin B receptor, and bombesin receptor subtype 3. All three receptors contain a conserved aspartate residue (D98) at the extracellular boundary of transmembrane domain II and a conserved arginine residue (R309) near the extracellular boundary of transmembrane domain VII. To evaluate the functional role of these residues, site-directed GRP-R mutants were expressed in fibroblasts and assayed for their ability to both bind agonist and catalyze exchange of guanine nucleotides. Alanine substitution at GRP-R position 98 or 309 reduced agonist binding affinity by 24- and 56-fold, respectively, compared to wild-type GRP-R. Single swap GRP-R mutations either resulted in no receptor expression in the membrane (D98R) or the protein was not able to bind agonist (R309D). In contrast, the double swap mutation (D98R/R309D) had high-affinity agonist binding, reduced from wild-type GRP-R by only 6-fold. In situ reconstitution of urea-extracted membranes expressing either wild-type or mutant (D98A or R309A) GRP-R with G(q) indicated that alanine substitution greatly reduced G protein catalytic exchange compared to wild-type GRP-R. The D98R/R309D GRP-R had both a higher intrinsic basal activity and a higher overall catalytic exchange activity compared to wild-type; however, the wild-type GRP-R produced a larger agonist-stimulated response relative to the double swap mutant. Taken together, these data show that GRP-R residues D98 and R309 are critical for efficient coupling of GRP-R to G(q). Furthermore, our findings are consistent with a salt bridge interaction between these two polar and oppositely charged amino acids that maintains the proper receptor conformation necessary to interact with G proteins.

The bombesin receptor subtypes have distinct G protein specificities

We used an in situ reconstitution assay to examine the receptor coupling to purified G protein alpha subunits by the bombesin receptor family, including gastrin-releasing peptide receptor (GRP-R), neuromedin B receptor (NMB-R), and bombesin receptor subtype 3 (BRS-3). Cells expressing GRP-R or NMB-R catalyzed the activation of squid retinal Galphaq and mouse Galphaq but not bovine retinal Galphat or bovine brain Galphai/o. The GRP-R- and NMB-R-catalyzed activations of Galphaq were dependent upon and enhanced by different betagamma dimers in the same rank order as follows: bovine brain betagamma > beta1gamma2 >> beta1gamma1. Despite these qualitative similarities, GRP-R and NMB-R had distinct kinetic properties in receptor-G protein coupling. GRP-R had higher affinities for bovine brain betagamma, beta1gamma1, and beta1gamma2 and squid retinal Galphaq. In addition, GRP-R showed higher catalytic activity on squid Galphaq. Like GRP-R and NMB-R, BRS-3 did not catalyze GTPgammaS binding to Galphai/o or Galphat. However, BRS-3 showed little, if any, coupling with squid Galphaq but clearly activated mouse Galphaq. GRP-R and NMB-R catalyzed GTPgammaS binding to both squid and mouse Galphaq, with GRP-R activating squid Galphaq more effectively, and NMB-R also showed slight preference for squid Galphaq. These studies reveal that the structurally similar bombesin receptor subtypes, in particular BRS-3, possess distinct coupling preferences among members of the Galphaq family.

Four amino acid residues are critical for high affinity binding of neuromedin B to the neuromedin B receptor

Three mammalian bombesin receptor subtypes have been characterized: the gastrin-releasing peptide receptor (GRP-R), the neuromedin B receptor (NMB-R), and bombesin receptor subtype 3 (BRS-3). In a previous report we identified four amino acids that are critical for high affinity binding of bombesin and gastrin-releasing peptide (GRP) to the GRP-R. These four amino acids are conserved in all species variants of the GRP-R and NMB-R which bind bombesin with high affinity, but they are diverged in BRS-3, the bombesin receptor subtype that binds bombesin with much lower affinity. Substituting these four divergent amino acids in BRS-3 for the conserved amino acids in either GRP-R or NMB-R increased the affinity of the mutated BRS-3 (4DeltaBRS-3) for bombesin compared with wild-type BRS-3. We hypothesized that the same four amino acids might be critical for high affinity NMB binding to the NMB-R. In this study we confirm this hypothesis by showing that the affinity of NMB is increased in a mutant BRS-3 receptor (4DeltaBRS-3) that contains these four substitutions resulting in an affinity that is close to the affinity of wild-type NMB-R for NMB. In contrast, these four amino acid substitutions in BRS-3 did not result in the formation of a high affinity binding site for the recently described non-peptide NMB-R antagonist PD168368.

Ability of various bombesin receptor agonists and antagonists to alter intracellular signaling of the human orphan receptor BRS-3

Bombesin (Bn) receptor subtype 3 (BRS-3) is an orphan receptor that is a predicted member of the heptahelical G-protein receptor family and so named because it shares a 50% amino acid homology with receptors for the mammalian bombesin-like peptides neuromedin B (NMB) and gastrin-releasing peptide. In a recent targeted disruption study, in which BRS-3-deficient mice were generated, the mice developed obesity, diabetes, and hypertension. To date, BRS-3's natural ligand remains unknown, its pharmacology unclear, and cellular basis of action undetermined. Furthermore, there are few tissues or cell lines found that express sufficient levels of BRS-3 protein for study. To define the intracellular signaling properties of BRS-3, we examined the ability of [D-Phe6,beta-Ala11,Phe13, Nle14]Bn-(6-14), a newly discovered peptide with high affinity for BRS-3, and various Bn receptor agonists and antagonists to alter cellular function in hBRS-3-transfected BALB 3T3 cells and hBRS-3-transfected NCI-H1299 non-small cell lung cancer cells, which natively express very low levels of hBRS-3. This ligand stimulated a 4-9-fold increase in [3H]inositol phosphate formation in both cell lines under conditions where it caused no stimulation in untransfected cells and also stimulated an increase in [3H]IP1, [3H]IP2, and 3H]IP3. The elevation of [3H]IP was concentration-dependent, with an EC50 of 20-35 nM in both cell lines. [D-Phe6,beta-Ala11,Phe13,Nle14]Bn-(6-14) stimulated a 2-3-fold increase in [Ca2+]i, a 3-fold increase in tyrosine phosphorylation of p125(FAK) with an EC50 of 0.2-0.7 nM, but failed to either stimulate increases in cyclic AMP or inhibit forskolin-stimulated increases. None of nine naturally occurring Bn peptides or three synthetic Bn analogues reported to activate hBRS-3 did so with high affinity. No high affinity Bn receptor antagonists had high affinity for the hBRS-3 receptor, although two low affinity antagonists for gastrin-releasing peptide and NMB receptors, [D-Arg1,D-Trp7,9, Leu11]substance P and [D-Pro4,D-Trp7,9,10]substance P-(4-11), inhibited hBRS-3 receptor activation. The NMB receptor-specific antagonist D-Nal,Cys,Tyr,D-Trp,Lys,Val, Cys,Nal-NH2 inhibited hBRS-3 receptor activation in a competitive fashion (Ki = 0.5 microM). Stimulation of p125(FAK) tyrosine phosphorylation by hBRS-3 activation was not inhibited by the protein kinase C inhibitor, GF109203X, or thapsigargin, alone or in combination. These results show that hBRS-3 receptor activation increases phospholipase C activity, which causes generation of inositol phosphates and changes in [Ca2+]i and is also coupled to tyrosine kinase activation, but is not coupled to adenylate cyclase activation or inhibition. hBRS-3 receptor activation results in tyrosine phosphorylation of p125(FAK), and it is not dependent on activation of either limb of the phospholipase C cascade. Although the natural ligand is not a known bombesin-related peptide, the availability of [D-Phe6,beta-Ala11, Phe13,Nle14]Bn-(6-14), which functions as a high affinity agonist in conjunction with hBRS-3-transfected cell lines and the recognition of three classes of receptor antagonists including one with affinity of 0.5 microM, should provide important tools to assist in the identification of its natural ligand, the development of more potent selective receptor antagonists and agonists, and further exploration of the signaling properties of the hBRS-3 receptor.

Identification of a unique ligand which has high affinity for all four bombesin receptor subtypes

Four subtypes of bombesin receptors are identified (gastrin-releasing peptide receptor, neuromedin B receptor, the orphan receptor bombesin receptor subtype 3 (BB3 or BRS-3) and bombesin receptor subtype 4 (BB4)), however, only the pharmacology of the gastrin-releasing peptide receptor has been well studied. This lack of data is due in part to the absence of a general ligand. Recently we have discovered a ligand, 125I-[D-Tyr6,betaAla11,Phe13,Nle14]bombesin-(6-1 4) that binds to BRS-3 receptors. In this study we investigate its ability to interact with all four bombesin receptor subtypes. In rat pancreatic acini containing only gastrin-releasing peptide receptor and in BB4 transfected BALB cells, this ligand and 125I-[Tyr4]bombesin, the conventional gastrin-releasing peptide receptor ligand, gave similar results for receptor number, affinity for bombesin and affinity for the unlabeled ligand. In neuromedin B receptor transfected BALB cells, this ligand and 125I-[D-Tyr0]neuromedin B, the generally used neuromedin B receptor ligand, gave similar results for receptor number, neuromedin B affinity or the unlabeled ligand affinity. Lastly, in BRS-3 transfected BALB cells, only this ligand had high affinity. For all four bombesin receptors this ligand had an affinity of 1-8 nM and was equal or greater in affinity than any other specific ligands for any receptor. The unlabeled ligand is specific for gastrin-releasing peptide receptors on rat pancreatic acini and did not inhibit binding of 125I-cholecystokinin octapeptide (125I-CCK-8), 125I-vasoactive intestinal peptide (125I-VIP) or 125I-endothelin to their receptors. The unlabeled ligand was an agonist only at the gastrin-releasing peptide receptor in rat acini and did not interact with CCK(A) receptors or muscarinic M3 acetylcholine receptors to increase [3H]inositol phosphates. These results demonstrate 125I-[D-Tyr6,betaAla11,Phe13,Nle14]bombesin-(6-1 4) is a unique ligand with high affinity for all subtypes of bombesin receptors. Because of the specificity for bombesin receptors, this ligand will be a valuable addition for such pharmacological studies as screening for bombesin receptor agonists or antagonists and, in particular, for investigating BRS-3 cell biology, a receptor for which no ligand currently exists.

Discovery of a high affinity radioligand for the human orphan receptor, bombesin receptor subtype 3, which demonstrates that it has a unique pharmacology compared with other mammalian bombesin receptors

An orphan receptor discovered in 1993 was called bombesin receptor subtype 3 (BRS-3) because of 47-51% amino acid identity with bombesin (Bn) receptors. Its pharmacology is unknown, because no naturally occurring tissues have sufficient receptors to allow studies. We made two cell lines stably expressing the human BRS-3 (hBRS-3). hBRS-3 was overexpressed in the human non-small cell lung cancer cells, NCI-H1299, and the other was made in Balb 3T3 cells, which lack endogenous BRS-3. [D-Phe6,beta-Ala11,Phe13, Nle14]Bn-(6-14) (where Nle represents norleucine) was discovered to have high potency for stimulating inositol phosphate formation in both cell lines. [125I-D-Tyr6,beta-Ala11,Phe13, Nle14]Bn-(6-14) bound to both cell lines with high affinity. Neither Bn nor 14 other naturally occurring Bn peptides bound to hBRS-3 with a Kd <1000 nM. Twenty-six synthetic peptides that are high affinity agonists or antagonists at other bombesin receptors had an affinity >1000 nM. Guanosine 5'-(beta,gamma-imido)triphosphate inhibited binding to both cells due to a change in receptor affinity. These results demonstrate hBRS-3 has a unique pharmacology. It does not interact with high affinity with any known natural agonist or high affinity antagonist of the Bn receptor family, suggesting the natural ligand is either an undiscovered member of the Bn peptide family or an unrelated peptide. The availability of these cell lines and the hBRS-3 ligand should facilitate identification of the natural ligand for BRS-3, its pharmacology, and cell biology.

Identification of four amino acids in the gastrin-releasing peptide receptor that are required for high affinity agonist binding

The bombesin family of G-protein-coupled receptors includes the gastrin-releasing peptide receptor (GRP-R), the neuromedin B receptor (NMB-R), bombesin receptor subtype 3 (BRS-3), and bombesin receptor subtype 4 (bb4). All species homologues of GRP-R, NMB-R, and bb4 bind bombesin with dissociation constants in the nanomolar range; by comparison, human BRS-3 binds bombesin at much lower affinity (Kd >> 1 microM). We used this difference to help identify candidate residues that were potentially critical for forming the bombesin binding pocket. We reasoned that amino acids essential for bombesin binding would be conserved among all homologues of bb4, NMB-R, and GRP-R; conversely, at least one of these amino acids would not be conserved among homologues of BRS-3. Amino acid sequence alignment revealed nine residues that fit this model. We replaced each of these amino acids in mouse GRP-R with the homologous amino acid in human BRS-3. Four substitutions resulted in a significant decrease in bombesin affinity (R288H, Q121R, P199S, and A308S). The analogous mutations in BRS-3 (R127Q, H294R, S205P, and S315A) together resulted in a receptor with a 100-fold increase in bombesin and GRP affinities relative to wild-type BRS-3. From this, we propose a preliminary map of some of the amino acids comprising the agonist binding pocket.

The gastrin-releasing peptide receptor is rapidly phosphorylated by a kinase other than protein kinase C after exposure to agonist

Several guanine nucleotide-binding protein-coupled receptors are known to be rapidly phosphorylated after agonist exposure. In this study we show that the gastrin-releasing peptide receptor (GRP-R) is rapidly phosphorylated in response to agonist exposure. When [32P]orthophosphate-labeled cells were exposed to bombesin, the receptor was maximally phosphorylated on serine and threonine residues within 1 min. Although addition of 12-O-tetradecanoylphorbol 13-acetate also resulted in phosphorylation of the GRP-R, elimination of protein kinase C activity using the inhibitor 7-hydroxystaurosporine did not prevent bombesin-induced GRP-R phosphorylation. We conclude that a kinase other than protein kinase C is principally responsible for the rapid, agonist-induced phosphorylation of the GRP-R.

Jasplakinolide's inhibition of the growth of prostate carcinoma cells in vitro with disruption of the actin cytoskeleton

BACKGROUND

Jasplakinolide, a cyclodepsipeptide produced by an Indo-Pacific sponge, Jaspis johnstoni, has been reported to inhibit the growth of breast cancer cells.

PURPOSE

The effects of jasplakinolide on the proliferation of three human immortalized prostate carcinoma cell lines (PC-3, LNCaP, and TSU-Pr1) were studied. The growth-inhibitory effect of jasplakinolide on the PC-3 cell line was studied in detail to elucidate its mechanism of action.

METHODS

Cell counts were used to study growth inhibition. A protein-based microplate assay was used to assess the time of exposure needed to cause persistent growth inhibition and to study the effects of jasplakinolide analogues. Metabolic changes were assessed by following the incorporation of radiolabeled precursors. The effects of jasplakinolide on the cytoskeleton were studied by fluorescent microscopy, using rhodamine phalloidin (RP) and antibodies to cytoskeletal components. Changes in RP binding were quantified by extracting bound fluorescent material from fixed cells and measuring the amount of fluorescence in a spectrofluorometer.

RESULTS

The growth of PC-3, LNCaP, and TSU-Pr1 cells was potently inhibited by exposure to jasplakinolide for 48 hours; doses of jasplakinolide that led to 50% growth inhibition were 65 nM for PC-3 cells, 41 nM for LNCaP cells, and 170 nM for TSU-Pr1 cells. In PC-3 cells, exposure to 160 nM for 48 hours led to total growth inhibition, which persisted for several days even after drug removal. Several jasplakinolide analogues also inhibited the growth of PC-3 cells, although analogues in which the rigidity of the macrolide ring was altered were ineffective. No early changes in the synthesis of DNA, RNA, or protein or in intracellular adenosine triphosphate levels were seen in the PC-3 cells after exposure to jasplakinolide. Growth inhibition by jasplakinolide was accompanied by striking morphologic changes. Exposure for several doublings led to multinucleated cells. Further investigation of these changes in the PC-3 cells revealed a dramatic and early disruption of the actin cytoskeleton and a statistically significant decrease in RP binding. The doses of jasplakinolide, the time of exposure, and the pattern of growth inhibition by structural analogues corresponded with the changes seen in actin distribution.

CONCLUSIONS

Jasplakinolide represents a novel marine natural product with potent in vitro antiproliferative activity against human prostate carcinoma cell lines, and it appears to target the actin cytoskeleton.

IMPLICATIONS

Jasplakinolide is a potential candidate for further preclinical development and a lead structure for a novel class of therapeutic agents that can disrupt the actin cytoskeleton in mammalian cells.

Preliminary study of treatment of sulphuric pickling water waste from steelmaking by bio-oxidation with Thiobacillus ferrooxidans

This report looks at the laboratory-scale recovery of iron oxides (alpha Fe2O3 type) through bio-oxidation with Thiobacillus ferrooxidans of the ferrous sulphate contained in steel industry sulphuric pickling liquors. This is done by calcining iron sulphates and iron and ammonium sulphates obtained from the crystallization of the oxidized solution. The products of the bacterial reaction and the iron oxides are then studied according to calcination temperature. The process carried out produced 50 kg of alpha Fe2O3 per m3 of waste pickling liquor at 700 degrees C with 99.8% weight iron recovery.

Dietary fish oil-induced changes in the distribution of alpha-tocopherol, retinol, and beta-carotene in plasma, red blood cells, and platelets: modulation by vitamin E

Healthy men (ages 24-57 y) were fed a controlled basal diet supplemented with 15 g/d of placebo oil (PO) for 10 wk followed by 15 g/d of fish-oil concentrate (FO) (fortified with 15 mg all-rac-tocopherol) for 10 wk without additional alpha-tocopherol and the last 8 wk with 200 mg alpha-tocopherol/d (FO+E). Compared with PO, FO raised plasma malondialdehyde; lowered alpha-tocopherol in plasma, red blood cells, and platelets; and raised plasma and platelet beta-carotene. Supplementation with additional alpha-tocopherol (FO+E) not only restored tocopherol concentrations but also reversed the rise in beta-carotene. The response in retinol, particularly in platelets, showed an inverse relationship to beta-carotene, alpha-tocopherol exhibiting a modulating effect on these changes. From these observations it is postulated that platelets may be a significant extraintestinal site of retinol formation from beta-carotene.

Stabilization of intercellular contacts in MDCK cells during Ca2+ deprivation. Selective effects of monocarboxylic acids on desmosomes

Short-chain monocarboxylic acids (MCAs) selectively protect desmosomal junctions of MDCK cells from disruption by chelating agents and low calcium medium. This effect occurs in the millimolar concentration range and increases inversely with carbon chain length (formate > acetate = propionate > butyrate > isobutyrate > isovalerate). The relative activity of MCAs does not correlate with their overall hydrophobicity or ability to chelate ions, or their effectiveness in lowering cytosolic pH. It exhibits chemical specificity and is dependent upon postconfluency culture age. MCAs also inhibit cell rounding produced by low concentrations of aminocarboxylate-chelating agents. Their effect on cell rounding, but not on desmosomes, can be antagonized by okadaic acid. The possibility is discussed that MCAs may produce their effects by binding specifically to protein(s) associated with the desmosome of mature, fully polarized MDCK monolayers.

Quantitative assessment of the genotoxicity of fecapentaenes

Fecapentaenes are a group of fecal mutagens of microbial origin isolated from human stools. Fecapentaene-12 (F-12) and fecapentaene-14 (F-14), differing only in two carbon atoms in the side chain, are glyceryl ethers with a highly reactive chromophoric aliphatic side chain incorporating a conjugated pentaene moiety. Although these compounds are known for their genotoxicity, no test systems have been developed to precisely assess their relative genotoxicity. In this study F-12 and F-14 were assayed for their genotoxicity using the SOS Chromotest in which the induction of beta-galactosidase in E. coli PQ37 was used as a quantitative measure of biological activity. The activity obtained with F-12 and F-14 was compared with that of 4-nitroquinoline oxide (4-NQO) as the reference standard of a direct acting mutagen. While F-14 was almost as active as 4-NQO, F-12 was only about 25% as active as F-14, the higher analog.

Influence of dietary fat on fecal mutagenicity in premenopausal women

A dietary intervention study was conducted on 31 premenopausal women (age: 20-40 years) to investigate the relationship between dietary fat and fecal mutagenicity. After a free-living period (baseline) of one menstrual cycle, the subjects were placed on a high-fat diet (40% calories from fat) for 4 menstrual cycles, followed by a low-fat diet (20% calories from fat) for 4 menstrual cycles. One-half of the subjects were randomly assigned throughout the study to a diet with a P:S ratio of 1.0 while the other half was assigned to one with a P:S ratio of 0.3; body weight by group remained constant. Three-day stool samples were collected at the mid-follicular period during the free-living phase and during the 4th menstrual cycle of each of the 2 controlled diet periods. Mutagenicity was assayed by the SOS chromotest. Reduction of dietary fat was accompanied by a significant decrease in fecal mutagenicity in both P:S groups. Combined values, i.e., both P:S groups, were 20.3 units for high-fat diets vs. 8.78 for low-fat diets.

Acyl chain interactions and the modulation of phase changes in glycerolipids

Fluorescence polarization measurements with 1,6-diphenyl-1,3,5-hexatriene and differential scanning calorimetry (DSC) were used to monitor phase transitions and order in the liquid state in sonicated dispersions of mono-, di- and triacylglycerols. Residual order in melted glycerolipids was indicated when the structural order parameter, S, assumed non-zero values at temperatures, t greater than or equal to tf, the DSC-determined fusion temperature. Residual order was observed with cis unsaturated di- and triacylglycerols but not with corresponding trans unsaturated or with saturated compounds. The reduced fluidity was attributed to adjacent binding of fatty acids to the glycerol molecule and the resulting interactions between fatty acyl moieties and packing effects. Lipids were considered as in an isotropic liquid or highly fluid state when diphenylhexatriene fluorescence anisotropy, rs, was equal to or less than 0.08, corresponding to S = 0. Temperatures, t0.08, for transition from the fluid state upon cooling were noted when rs = 0.08, and delta t = t0.08-tf was then taken as a measure of residual order. Tri-, 1,2-di and 1,3-dioleoylglycerol delta t values were 75, 60.9 and 13.6 degrees C, respectively. Tri-, 1,3-di- and monolinoleoylglycerol delta t values were 86, 30 and 41 degrees C, respectively. Restrictions in mobility when observed are attributable to interactions between adjacent acyl chains. Double bond location in the hydrocarbon chain affected ordering in the liquid state as simple triacylglycerol esters of cis 18:1 delta 6, trans 18:1 delta 6 and cis 24:1 delta 15 exhibited t = 37, 14 and 18 degrees C, respectively.

The mediating role of the parathyroid gland in the effect of low calcium intake on blood pressure in the rat

Recent reports suggest an inverse relationship between calcium intake and blood pressure. This effect could be mediated by parathormone (PTH), since a low calcium intake leads to an increase in PTH and this hormone produces an increase in intracellular calcium, raising the excitability of the muscle arteriolar cells. Wistar female rats, 56 days old, were submitted to a parathyroidectomy or to a sham operation. After that, they were placed on a normal or on a calcium-free diet during 10 weeks. Four groups of nine rats were studied: parathyroidectomized animals on a normal calcium diet, parathyroidectomized ones on a calcium-free diet, controls (sham operation) on a normal calcium diet, and controls (sham operation) on a calcium-free diet. The control calcium-free diet showed a significant increase in blood pressure values over the treatment period. The parathyroidectomized calcium-free diet group did not show any increase. The difference between these two groups regarding change in blood pressure was statistically significant. The parathyroidectomized-calcium-free group showed no weight increase during the study, while rats in the other three groups significantly increased their weight. PTH could be the mediator of the blood pressure rise observed in the calcium-deprived rats in spite of the possible confounding effect of the poor weight increase detected in the parathyroidectomized-calcium deprived animals. These results warrant future studies since the role of PTH in the regulation of blood pressure needs to be confirmed. This possibility, therefore, opens a new area of research in the study of the pathophysiology of hypertension.

Fluorescence polarization order parameters and phase transitions in lipids and lipoproteins

Fluorescence polarization measurements with 1,6-diphenyl-1,3,5-hexatriene (DPH) were used to monitor phase changes in sonicated dispersions of triacylglycerols, cholesteryl esters and phospholipids. Lipid transitions to a fluid state were detected in a novel way by noting the temperature, t0.08, at which rs, the steady state anisotropy, was equal to 0.08. According to published equations (Van Blitterswijk , W.J., Van Hoeven , R.P. and Van der Meer , B.W. (1981) Biochim. Biophys. Acta 644, 323-332), this value for rs corresponds to a value of zero for S, a structural order parameter. Saturated and trans monounsaturated fatty triacylglycerols and distearoylphosphatidylcholine yielded t0.08 values in close agreement with transition temperatures found by differential scanning calorimetry (DSC), whereas cis unsaturated triacylglycerols displayed residual anisotropy, rs greater than 0.08, at temperatures above the DSC transition. The bent configuration of the cis double-bonded fatty acyl chains probably limits freedom of movement even in the liquid state when three such chains are bound to the glycerol molecule. Cholesteryl esters of 14:0, 18:0 and cis 18:1 fatty acids all showed rs greater than 0.08 above the DSC melting point. The difference in rotational freedom of DPH in triacylglycerol and cholesteryl esters even in the 'liquid' state explains the low t0.08 in the more fluid plasma VLDL and the contrastingly high t0.08 in plasma LDL, and HDL, which contain more cholesteryl ester an less triacylglycerol.

Reduction of blood pressure with calcium supplementation in young adults

Epidemiologic and animal studies have suggested an inverse relationship between calcium intake and BP. Furthermore, calcium intake seems to be inversely correlated with the incidence of eclampsia in pregnancy. In a randomized clinical trial, young adults were allocated to a calcium-supplemented group receiving 1 g/day of elemental calcium (15 men and 15 women) or a placebo group (14 women and 13 men) for a period of 22 weeks. The calcium-supplemented group showed a significant decrease in diastolic BP; this effect was stabilized after nine weeks in women and six weeks in men. The reduction in diastolic BP was 5.6% and 9% from the initial values for women and men, respectively. This study supports epidemiologic and animal evidence of the effect of calcium intake on BP and suggests the need for more research exploring the mechanisms involved in the observed effect.

Rise of blood pressure in calcium-deprived pregnant rats

It has been postulated that calcium uptake is inversely related to blood pressure (BP) in animals and pregnant women. To test this hypothesis, 34 female, 142-day-old Wistar rats were studied prospectively. They were randomly assigned to either a calcium-free diet (16 rats) or a normal diet (18 rats). Weekly measurements of tail systolic BP showed a statistically significant increase in BP in the calcium-free group after 6 weeks of treatment. After 9 weeks on this diet, the animals were mated. Five in the control group and six in the calcium-free group became pregnant. Thereafter, both of these subgroups (pregnant and nonpregnant calcium-free diet) continued with significantly higher BP until they were put to death. Blood samples taken at the end of the study showed significantly lower values of calcium/magnesium (Ca/Mg) ratio, but higher inorganic phosphate in the group consuming a calcium-free diet. Blood pressure during the last 3 weeks of the study was significantly inversely correlated with the blood Ca/Mg ratio and directly correlated with magnesium and inorganic phosphate values. This article supports the hypothesis that a low-calcium diet is associated with high BP in pregnant and nonpregnant female rats.