Diagnostic value of anti-integrin αvβ6 antibodies in ulcerative colitis

Ulcerative colitis (UC)-related mucosal inflammation is characterized by the production of various autoantibodies with limited clinical relevance. Recent studies have shown that circulating levels of IgG against integrin αvβ6 are increased in UC patients as compared to Crohn's disease (CD) patients and healthy controls (HC). The present study assessed the diagnostic value of circulating IgG anti-αvβ6 in UC. Sera were prospectively collected from 108 outpatients with UC, 103 patients with CD, and 62 HC, and the levels of IgG anti-αvβ6 were measured using a commercially available ELISA kit. The cut-off for positive results was defined as the 95th percentile of the values of the autoantibodies in HC serum samples. Levels of IgG anti-αvβ6 were significantly higher in UC than in CD patients, including those with colonic localization, and HC. Fifty-six of the 108 (51.8%) UC patients had a positive test whereas only 17/103 (16.5%) patients with CD, and among these, 4/16 (25%) patients with colonic CD, were positive. In UC, there was no statistical difference between patients with IgG anti-αvβ6 positivity and those negative in terms of clinical disease activity, fecal calprotectin values, and disease extent. The sensitivity, specificity, predictive positive value, and predictive negative value of the test to differentiate between UC and CD were 51.9% (C.I.42.4-61.3), 83.5% (C.I. 76.3-90.7), 76.7% (C.I. 67.0-86.4), and 62.3% (C.I. 54.2-70.4) respectively. Our study confirms that anti-αvβ6 antibodies are demonstrable in the serum of the majority of UC patients and suggests the necessity of further research to understand if the anti-αvβ6 antibody determination could have a place in the clinical decision-making of IBD.

Emerging oral drug options for ulcerative colitis

INTRODUCTION

Despite the availability of a variety of therapeutic compounds and improved management strategies, one-third of UC patients with moderate-to-severe disease do not benefit from the existing treatments or experience drug-related side effects. This has boosted intensive research focusing on the development of new drugs for UC therapy. This article aims to summarize the available evidence on oral drugs, which are now being explored in clinical trials or are ready to enter the clinics.

AREAS COVERED

From May 15 to June 11, we searched on PubMed using the keywords 'oral drugs ulcerative colitis,' 'ulcerative colitis clinical trials,' 'UC phase 2 and 3 trials' excluding case reports, case series, phase 1 and 4 studies, and studies about approved therapies.

EXPERT OPINION

The findings discussed in this article suggest that the future treatment of UC patients will be probably characterized by the possibility of using various small-molecule drugs. All these new compounds, even those belonging to the same class, differ in terms of efficacy and safety. Identification of predictors of response could help optimize the efficacy and safety of these treatments, thus improving resource allocation through a pretreatment stratification of patients.

Frail Phenotype in Patients With Inflammatory Bowel Disease

BACKGROUND

Recent retrospective studies have shown that frailty is common in hospitalized patients with inflammatory bowel disease (IBD) and enhances the risk of drug-related infections, postsurgery complications, hospital readmissions, and mortality, independently of age and comorbidities. We carried out a descriptive cohort study to evaluate the frequency of frail phenotype in IBD and analyzed the risk factors associated with this condition.

METHODS

Frail phenotype was assessed in IBD patients by using the Fried frailty phenotype. Univariate and multivariate analyses were conducted to assess the risk factors for frail phenotype. Serum levels of interleukin (IL)-6 were quantified in patients with a frail or a fit phenotype by ELISA.

RESULTS

Three hundred eighty-six IBD outpatients (198 Crohn's disease and 188 ulcerative colitis) were prospectively enrolled from December 2021 to April 2022. Frail phenotype was diagnosed in 64 of 386 (17%) IBD patients and was significantly associated with female gender, active disease, and current use of steroids. Multivariate analysis showed that active disease was a risk factor for frail phenotype (odds ratio, 11.5; 95% confidence interval, 3.9-33.9). No difference in IL-6 serum levels was seen between patients with a frail phenotype and those who were fit.

CONCLUSIONS

This is the first prospective study showing that frail phenotype occurs in nearly one-fifth of IBD patients. Data indicate that active IBD is an independent risk factor for frail phenotype in IBD.

Immune-mediated inflammatory diseases: Common and different pathogenic and clinical features

The term "immune-mediated inflammatory diseases (IMIDs)" refers to several inflammatory pathologies of multifactorial etiology and involving either simultaneously or sequentially more organs. IMIDs share some common pathogenic mechanisms, which account for some similarities in the clinical course and the impact that these diseases may have on other organs and systems of the body. However, there are some differences in the IMID-associated pathological process, including the synthesis and function of multiple inflammatory cytokines, which are supposed to perpetuate the tissue-damaging inflammation. This justifies the different indications and responsiveness to corticosteroids, immunosuppressors, small molecules, and biologics. Many individuals with IMIDs are, however, intolerant, or unresponsive to the current drugs, thus suggesting the necessity of novel therapeutic approaches, such as the combination of compounds that either inhibit more immuno-inflammatory networks selectively or simultaneously suppress inflammatory signals and activate counter-regulatory pathways. In this article, we highlight the most relevant features of IMIDs and discuss how clinicians can combat the detrimental immune response in such disorders.

Severe acute respiratory syndrome coronavirus 2 infection does not worsen the course of inflammatory bowel disease in the long term

BACKGROUND

The long-term outcome of inflammatory bowel disease (IBD) patients after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is under investigation.

AIM

To assess, in a prospective study, whether a recent SARS-CoV-2 infection increases the risk of IBD relapse within 12 months.

METHODS

From March to April 2021, all IBD patients with recent (<2 months) SARS-CoV-2 infection (Cases) were enrolled. For each enrolled Case, four IBD Controls with no history of infection were considered. Clinical course of IBD was recorded for 12 months. Inclusion criteria: well defined diagnosis of IBD; age ≥18 and ≤85 years; 12-month follow-up; consent. Exclusion criteria: incomplete data; SARS-CoV-2 infection after enrollment. Additional inclusion criteria: recent SARS-CoV-2 infection for Cases; no history of SARS-CoV-2 infection for Controls. Data expressed as median [range]. Statistical analysis: Student-t-Test, Mann-Whitney U-test, χ2 test, multivariate logistic regression model [odds ratio (95% confidence interval)], Kaplan-Meier curves.

RESULTS

One hundred forty-three IBD patients were enrolled. The analysis included 118 patients (22 met the exclusion criteria, three lost at follow-up): 29 (24.6%) Cases and 89 (75.4%) Controls. Demographic and clinical characteristics were comparable between groups. During the 12-month study, the frequency of IBD relapse was comparable between Cases and Controls [8 (27%) vs 19 (21%); P = 0.65]. At univariate analysis, SARS-CoV-2 infection was not a risk factor for IBD relapse within 12 months [1.5 (0.6-3.9); P = 0.34]. At multivariate analysis, IBD activity at baseline was the only risk factor for relapse [3.2 (1.1-9.1); P = 0.03]. Kaplan-Meier curves showed that survival from IBD relapse was comparable between Cases and Controls (P = 0.33).

CONCLUSION

In a prospective 12-month study, a recent SARS-CoV-2 infection did not increase the risk of clinical relapse of IBD in the long term.

Mucinous and Signet-Ring Cell Colonic Adenocarcinoma in Inflammatory Bowel Disease: A Case-Control Study

A higher frequency of mucinous and signet-ring cell colonic adenocarcinoma has been reported in inflammatory bowel disease (IBD). The primary aim was to investigate the frequency of mucinous and signet-ring cell colorectal adenocarcinoma in patients with IBD (Cases) versus age-matched non-IBD Controls. The secondary aims were to compare the characteristics of these two histotypes of colorectal cancer (CRC) in IBD patients vs. Controls and to search for specific risk factors in IBD. In a case-control study, all IBD patients with CRC diagnosed from 2000 to 2022 were enrolled and matched for age (1:2) with non-IBD Controls with CRC. The study population included 120 CRC patients (40 IBD, 80 Controls). In IBD, CRC included standard adenocarcinoma in 23 (57.5%) patients mucinous/signet-ring cell adenocarcinoma in 17 (42.5%) patients. The proportion of mucinous/signet-ring cell adenocarcinoma was higher in IBD than in Controls (17 [42.5%] vs. 18 [22.5%]; p = 0.03). In rectal CRC, the proportion of mucinous/signet-ring cell adenocarcinoma was higher than standard adenocarcinoma in IBD (8 [47.1%] vs. 4 [17.4%]; p = 0.04) but not in Controls (4 [22.2%] vs. 20 [32.2%]; p = 0.59). In rectal CRC, the proportion of these two histotypes was higher in Cases than in Controls (8/12 [66.6%] vs. 4/24 [16.6%]; p = 0.008), with no risk factors identified in IBD. CRC was more frequently represented by mucinous/signet-ring cell adenocarcinoma in IBD than in age-matched non-IBD Controls. In IBD, these two CRC histotypes were more frequent in the rectum.

Niclosamide Enema for Active Distal Ulcerative Colitis: A Phase 1, Open-Label Study

BACKGROUND

Oral and rectal formulations of 5-aminosalicylic acid are the first-line therapy for mild-to-moderate, distal ulcerative colitis (UC), but such a treatment is not effective in one-third of patients. Niclosamide is a small molecule, developed and approved as an orally administered drug to treat helminthic infections, with an excellent safety profile. Preclinical work showed that niclosamide is an anti-inflammatory agent, thereby providing the rationale to explore its safety and efficacy in patients with UC. This phase 1, open-label trial was aimed at assessing the safety of niclosamide formulated as an enema in patients with mild-to-moderate, distal UC, who relapsed on maintenance therapy with oral and/or rectal 5-aminosalicylic acid.

METHODS

Seventeen patients with active UC received niclosamide enema (150 mg/60 mL) twice a day for 6 weeks. The primary endpoint was the safety of niclosamide treatment. Secondary endpoints included clinical remission and improvements in endoscopic Mayo/histologic scores. Endoscopic remission percentages exclude participants meeting criteria at baseline for endoscopic remission.

RESULTS

Niclosamide was well tolerated by all 17 patients that were enrolled and treated. No serious adverse event was registered. Fifteen mild adverse events were registered in 6 patients and considered to be unrelated to the treatment. Clinical remission was achieved in 10 (59%) of 17 patients. Improvements of endoscopic Mayo score and histologic Geboes score were seen in 7 (58%) of 12 and 7 (41.2%) of 17 patients, respectively.

CONCLUSIONS

Niclosamide enema treatment is safe and well tolerated. Niclosamide improves clinical symptoms and endoscopic/histologic signs of UC; however, appropriately designed placebo-controlled clinical trials are required to confirm efficacy.

Reversibility of Frail Phenotype in Patients with Inflammatory Bowel Diseases

It was recently reported that frailty status can negatively influence the clinical course of patients with inflammatory bowel diseases (IBDs). Our recent study demonstrated that 20% of patients with an IBD are frail, and disease activity increases the risk of frailty. In the present study, we prospectively monitored this subgroup of frail patients, assessed whether the frailty status was reversible, and analyzed factors associated with frailty reversibility. Of the sixty-four frail patients with IBD enrolled, five (8%) were lost during the follow-up period and one (2%) underwent a colectomy. Eleven out of the fifty-eight (19%) patients maintained a frail phenotype during a median follow-up of 8 months (range 6–19 months), and thirty-five (60%) and twelve (21%) became pre-frail or fit, respectively. A comparison of the 58 patients at baseline and at the end of the study showed that frail phenotype reversibility occurred more frequently in patients who achieved clinical remission. A multivariate analysis showed that the improvement of the frail phenotype was inversely correlated with the persistence of clinically active disease (OR:0.1; 95% CI: 0.02–0.8) and a history of extra-intestinal manifestations (OR:0.1; 95% CI: 0.01–0.6) and positively correlated with the use of biologics (OR: 21.7; 95% CI: 3.4–263). Data indicate that the frail phenotype is a reversible condition in most IBD patients, and such a change relies on the improvement in disease activity.

Hepcidin Upregulation in Colorectal Cancer Associates with Accumulation of Regulatory Macrophages and Epithelial-Mesenchymal Transition and Correlates with Progression of the Disease

Advanced, metastatic colorectal cancer (CRC) is associated with high rate of mortality because of its poor responsiveness to chemotherapy/immunotherapy. Recent studies have shown that hepcidin, a peptide hormone produced mainly by hepatocytes, is expressed by and enhances the growth of tumor cells. We here assessed whether hepcidin expression helps identify subsets of CRC with advanced and aggressive course. By integrating results of in vitro/ex vivo studies with data of bioinformatics databases, we initially showed that hepcidin RNA and protein expression was more pronounced in tissue samples taken from the tumor area, as compared to the macroscopically unaffected, adjacent, colonic mucosa of CRC patients. The induction of hepcidin in the colonic epithelial cell line HCEC-1ct by interleukin (IL)-6, IL-21 and IL-23 occurred via a Stat3-dependent mechanism and, in primary CRC cells, hepcidin co-localized with active Stat3. In CRC tissue, hepcidin content correlated mainly with macrophage accumulation and IL-10 and CD206 expression, two markers of regulatory macrophages. Consistently, both IL-10 and CD206 were up-regulated by hepcidin in blood mononuclear cells. The highest levels of hepcidin were found in metastatic CRC and survival analysis showed that high expression of hepcidin associated with poor prognosis. Moreover, hepcidin expression correlated with markers of epithelial-to-mesenchymal transition and the silencing of hepcidin in CRC cells reduced epithelial-to-mesenchymal transition markers. These findings indicate that hepcidin is markedly induced in the advanced stages of CRC and suggest that it could serve as a prognostic biomarker in CRC.

SARS-CoV-2 Igg seroprevalence in IBD patients treated with biologics: first vs. second pandemic wave in a prospective study

OBJECTIVE

In a prospective study, SARS-CoV-2 IgG seroprevalence was assessed during the second pandemic wave (W2) in a cohort of Inflammatory Bowel Disease (IBD) patients using biologics. The secondary aim was to compare, in the same cohort, the frequency of seropositivity and of COVID-19 during the second vs. the first (W1) wave.

PATIENTS AND METHODS

From November 2020 to March 2021, SARS-CoV-2 IgG seropositivity and the prevalence of COVID-19 were assessed in a cohort of IBD patients using biologics already studied at W1.

INCLUSION CRITERIA

age ≥ 18 years; diagnosis of IBD; follow-up; written consent.

EXCLUSION CRITERIA

SARS-CoV-2 vaccination. Risk factors for infection, compatible symptoms, history of infection or COVID-19, nasopharyngeal swab test were recorded. Data were expressed as median [range]. The χ2 test, Student's t-test, logistic regression analysis was used.

RESULTS

IBD cohort at W1 and W2 included 85 patients: 45 CD (52.9%), 40 UC (47.1%). When comparing the same 85 patients at W2 vs. W1, a higher SARS-CoV-2 seroprevalence at W2 was at the limit of the statistical significance (9.4% vs. 2.3%; p=0.05). The prevalence of COVID-19 at W2 vs. W1 was 3.5% (3/85) vs. 0% (0/85) (p=0.08). Contacts with COVID-19 patients and symptoms compatible with COVID-19 were more frequent at W2 vs. W1 (18.8 % vs. 0%; p=0.0001; 34.1% vs. 15.3%; p=0.004). At W2, history of contacts and new onset diarrhea were more frequent in seropositive patients [4/8 (50%) vs. 12/77 (15.6%); p=0.01 and 4/8 (50%) vs. 2/77 (2.6%); p=0.0001]. At W2, the risk factors for seropositivity included cough, fever, new onset diarrhea, rhinitis, arthromyalgia, dysgeusia/anosmia at univariate (p<0.05), but not at multivariate analysis. History of contacts was the only risk factor for seropositivity at univariate (p=0.03), but not at multivariate analysis (p=0.1).

CONCLUSIONS

During W2, characterized by a high viral spread, IBD and biologics appeared not to increase the prevalence of SARS-CoV-2 infection or COVID-19 disease. New onset diarrhea mimicking IBD relapse may be observed in patients with SARS-CoV-2 infection.

Long-Term Risk of Colectomy in Patients with Severe Ulcerative Colitis Responding to Intravenous Corticosteroids or Infliximab

Background and aims: Intravenous corticosteroids (IVCS) and rescue therapy with infliximab (IFX) are useful for managing patients with acute severe ulcerative colitis (ASUC). However, nearly one fifth of responders undergo colectomy. Predictive factors of colectomy in this subset of patients are not fully known. We retrospectively examined the long-term risk and the predictors of colectomy in ASUC patients achieving clinical remission following treatment with IVCS or IFX. Patients and methods: Clinical and demographic characteristics were evaluated in consecutive ASUC patients who were admitted to the “Tor Vergata University” hospital between 2010 and 2020 and responded to IVCS or IFX. A multivariate logistic regression model was constructed to identify independent predictors of colectomy. Results: A total of 116 ASUC patients responding to IVCS (98 patients) or IFX (18 patients) were followed up for a median of 46 months. After discharge, 29 patients (25%) underwent colectomy. Multivariate analysis showed that a serum albumin level <3 g/dL and colonic dilation >5.5 cm on admission were independent predictors of colectomy (OR: 6.9, 95% CI: 2.08−22.8, and OR 8.5, 95% CI: 1.23−58.3, respectively). Patients with both these factors had a risk of colectomy 13 times greater than those with no risk factor. Conclusions: A low serum albumin level and colonic dilation are risk factors of long-term colectomy in ASUC patients responding to IVCS or IFX.

Interleukin-34 promotes tumorigenic signals for colon cancer cells

Colorectal carcinoma (CRC) is one of the most common forms of malignancy in the Western world. Accumulating evidence indicates that colon carcinogenesis is tightly controlled by tumour-associated immune cells and stromal cells, which can either stimulate or suppress CRC cell growth and survival, mainly via the production of cytokines. Interleukin-34 (IL-34), a cytokine known to regulate mainly monocyte/macrophage survival and function, is highly produced within the CRC microenvironment by several cell types, including cancer cells, tumour-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs), and regulates the pro-tumoural functions of such cells. In this article, we summarize the available data supporting the multiple effects of IL-34 in human CRC.

Natural History of Ulcerative Colitis with Coexistent Colonic Diverticulosis

Ulcerative colitis (UC) and colonic diverticulosis can co-exist in some patients. However, the natural history of UC associated with colonic diverticulosis is not well known. We here compared the disease characteristics and outcome of UC patients with and without concomitant colonic diverticulosis. Medical records of 347 UC patients were included in an observational, retrospective, nested-matched case-control study. Cases were 92 patients with UC and concomitant colonic diverticulosis, while controls were 255 UC patients without concomitant colonic diverticulosis. A propensity score matching (PSM) was used to homogenate cases (n = 92) and controls (n = 153) for age. UC patients with concomitant colonic diverticulosis were less likely to have an extensive disease (25/92, 27.1%) and to experience steroid dependence (8/92, 8.6%) compared to patients without concomitant colonic diverticulosis (70/153, 45.7% and 48/153, 31.3%, respectively; p < 0.001). The use of immunosuppressants (9/92, 9.7% vs. 37/153, 24.1%; p = 0.007) or biologics (3/92, 3.2% vs. 26/153, 16.9%, p < 0.001) was significantly lower in UC patients with concomitant diverticulosis compared to the control group. On multivariate analysis, steroid dependence and extensive colitis were significantly less frequent in UC patients with concomitant colonic diverticulosis compared to UC patients without diverticula. UC patients with coexisting colonic diverticulosis are less likely to have an extensive disease and to be steroid-dependent.

Low Frequency of Acute Pancreatitis in Hospitalized COVID-19 Patients

OBJECTIVE

The clinical significance of increased serum pancreatic enzymes (PEs) in coronavirus disease 2019 (COVID-19) patients has not yet been fully understood. We aimed to investigate the frequency and the impact on clinical outcome of PE elevation and acute pancreatitis in such patients.

METHODS

Clinical data, laboratory tests, and cross-sectional images were analyzed from COVID-19 patients admitted to the Tor Vergata Hospital in Rome. Variables associated with PE abnormalities, intensive care unit (ICU) admission, or death were investigated through univariate and multivariate analyses and Cox proportional hazard model.

RESULTS

Pancreatic enzymes were available in 254 of 282 COVID-19 patients. Among these, 66 patients (26%) showed mild elevation of PE, and 11 patients (4.3%) had severe elevation (>3 times of the upper limit of normal). Overall, 2 patients met the diagnostic criteria for acute pancreatitis. Hepatic and renal involvements were associated with PE elevation. Multivariate analysis showed that mild and severe PE elevations were significantly associated with ICU admission (odds ratios, 5.51 [95% confidence interval, 2.36-12.89; P < 0.0001] and 26.2 [95% confidence interval, 4.82-142.39; P < 0.0001]).

CONCLUSIONS

Increase in serum PE, but not acute pancreatitis, is frequent in hospitalized COVID-19 patients and associates with ICU admission.

No effect of a liquid diet in the management of patients with stricturing Crohn's disease

PURPOSE

Patients with stricturing Crohn's disease (CD) may experience episodes of intestinal sub-occlusions, which in many cases lead to surgery. The aim of this study was to examine whether adding a liquid diet to medical therapy could improve the management of patients with stricturing CD.

METHODS

Medical records of CD outpatients with a small bowel stricture, either receiving (group 1) or not (group 2) a 24-h liquid diet every 10-14 days, were retrospectively analyzed. Number of sub-occlusive episodes, frequency, and timing of intestinal resections for strictures were analyzed.

RESULTS

During the 12-month follow-up, there was no significant difference in the occurrence of new sub-occlusive episodes between the 2 groups (10/37 patients (27%) in group 1 vs 9/45 patients (20%) in group 2). Similarly, the number of patients undergoing bowel resections for sub-occlusive episodes non-responsive to medical therapy did not statistically differ between the two groups (9 patients (24.3%) in group 1 vs 7 patients (15.5%) in group 2). In group 1, surgeries were equally distributed along the 12-months of follow-up, while 85.7% of patients in group 2 underwent intestinal resection within the first 3 months of follow-up.

CONCLUSION

Adding a liquid diet to medical therapy does not help management of patients with stricturing CD.

TGF-β activity restoration and phosphodiesterase 4 inhibition as therapeutic options for inflammatory bowel diseases

In the last decades, the better understanding of inflammatory bowel diseases (IBD) pathogenesis has contributed to the identification of new therapeutic targets that can be modulated to induce and maintain disease remission. Monoclonal antibodies against tumor necrosis factor, interleukin (IL)-12/IL-23p40, and the integrin α4β7 and inhibitors of Janus kinase molecules are valid compounds to limit the function of molecules implicated in the control of IBD-related inflammation. However, not all patients respond to treatment with such drugs, some of them lose response over time and others develop serious side effects, such as infections or malignancies, which lead to the discontinuation of the therapy. Thus, an intensive research is ongoing with the goal to identify new targets and develop novel therapeutic options. In this context, restoration of TGF-β activity and inhibition of phosphodiesterase 4 (PD4) represent two relevant strategies. TGF-β is an immunesuppressive cytokine, whose activity is severely impaired in IBD due to the abundance of the intracellular inhibitor Smad7. Knockdown of Smad7 with a specific antisense oligonucleotide restores TGF-β signalling and dampens effector immune responses in pre-clinical studies and initial clinical trials in Crohn's disease patients, even though a recent phase 3 trial was discontinued due to an apparent inefficacy. PD4 inhibition determines the increase of intracellular levels of cyclic adenosine monophosphate, a mechanism that decreases pro-inflammatory cytokine production. A recent phase 2 study has shown that oral administration of PD4 associates with clinical benefit in patients with ulcerative colitis. In this article, we review the rationale and the available data relative to the use of these two agents in IBD.

Myotonic dystrophy protein kinase (DMPK) prevents ROS-induced cell death by assembling a hexokinase II-Src complex on the mitochondrial surface

The biological functions of myotonic dystrophy protein kinase (DMPK), a serine/threonine kinase whose gene mutations cause myotonic dystrophy type 1 (DM1), remain poorly understood. Several DMPK isoforms exist, and the long ones (DMPK-A/B/C/D) are associated with the mitochondria, where they exert unknown activities. We have studied the isoform A of DMPK, which we have found to be prevalently associated to the outer mitochondrial membrane. The kinase activity of mitochondrial DMPK protects cells from oxidative stress and from the ensuing opening of the mitochondrial permeability transition pore (PTP), which would otherwise irreversibly commit cells to death. We observe that DMPK (i) increases the mitochondrial localization of hexokinase II (HK II), (ii) forms a multimeric complex with HK II and with the active form of the tyrosine kinase Src, binding its SH3 domain and (iii) it is tyrosine-phosphorylated by Src. Both interaction among these proteins and tyrosine phosphorylation of DMPK are increased under oxidative stress, and Src inhibition selectively enhances death in DMPK-expressing cells after HK II detachment from the mitochondria. Down-modulation of DMPK abolishes the appearance of muscle markers in in vitro myogenesis, which is rescued by oxidant scavenging. Our data indicate that, together with HK II and Src, mitochondrial DMPK is part of a multimolecular complex endowed with antioxidant and pro-survival properties that could be relevant during the function and differentiation of muscle fibers.

Polycrystalline diamond UV-triggered MESFET receivers

Optically triggered UV sensitive receivers were fabricated on polycrystalline diamond as surface channel MESFETs. Opaque gates with asymmetric structure were designed in order to improve charge photogeneration mainly within the gate-drain region. Photogenerated holes contributed to the channel charge by assistance of the local electric field, in such a way improving the current signal at the drain contact. The sensitivity to UV light is demonstrated by using 3 ns wide laser pulses at 193 nm, well over the diamond bandgap. The receiver transient response to such laser pulses shows that the photogeneration process is only limited by the pulse rise time and charge collection at the drain contact completed in a time scale of a few nanoseconds. Such opaque gate three-terminal devices are suitable for application in emerging photonic technologies, for power-management system optical receivers, where copper wires and EM shielding can be replaced by lightweight optical fibers.

Characterization of the SnO2/a-SiC:H Interface in Amorphous Silicon Solar Cell by C-f-T Measurements

In this paper we present a new method for the characterization of the interface between the transparent conductive oxide (TCO) and the p doped amorphous silicon carbide layer in solar cells. The method is based on electrical capacitance measurements versus frequency in the temperature range: 20K-200K. We use Schottky diode structures (TCO-p-i-Ag) containing the p-i structure actually present in solar cells. Analysis of capacitance at different frequencies allows one to calculate an“activation energy”. Activation energy, temperature, position and shape of the capacitance step can be related to the density of states in the p type material by a model here presented. The effects of the p layer thickness and of the carbon content are investigated. A large increase of activation energy at short thickness is found, which can be related to interface damage, increasing in material with high carbon content. The technique shows an high spatial resolution and has the advantage to investigate the material as grown in the actual device.

Lower airway inflammation before and after house dust mite nasal challenge: an age and allergen exposure-related phenomenon

BACKGROUND

Upper and lower airways allergic disease is currently considered unitarily. Allergic inflammation in one site can extend to other sites of the respiratory tract.

OBJECTIVE

To evaluate bronchial inflammation before and after allergen-specific nasal challenge (ASNC) in rhinitic and asthmatic children, considering the different levels of allergen exposure, i.e. summer (low) and winter (high).

METHODS

Fourteen children with rhinitis and 15 with rhinitis and asthma, all monosensitized to mites and 10 healthy controls were studied. Nasal IgE were measured before ASNC in summer and in winter season. Nasal clinical score, eosinophil cationic protein (ECP), nasal tryptase, bronchial clinical score, FEV(1), PEF, sputum ECP, sputum tryptase and exhaled nitric oxide (eNO) were evaluated before and after ASNC in summer and winter season.

RESULTS

Nasal scores significantly increased after ASNC in rhinitic and asthmatic children in both seasons. Nasal IgE were significantly higher in summer compared to winter. Bronchial symptoms, FEV(1) and PEF showed no mean differences in rhinitic and asthmatic children after ASNC, with an increase of bronchial symptoms and a decrease of FEV(1) and PEF occurring in 3/15 asthmatic children. In both groups nasal tryptase and ECP after ASNC significantly increased in summer and winter, while sputum tryptase was undetectable before or after ASNC in both groups. Sputum ECP and eNO at baseline were significantly higher in patients than in controls (summer P=0.002, winter P=0.001). Sputum ECP significantly increased after ASNC in 3/15 asthmatics in summer and in 11/15 in winter, as well as in 3/14 rhinitics in summer and in 4/14 in winter. eNO significantly increased after ASNC in 3/15 asthmatics in summer and in 10/15 in winter, and in 1/14 rhinitics in summer and in 4/14 in winter. A significant median increase of sputum ECP (P=0.0007) and eNO (P=0.0012) after ASNC in asthmatic and of eNO (P=0.013) in rhinitic children was also found in winter.

CONCLUSIONS

Basal sputum ECP and eNO values, significantly higher before ASNC in rhinitic patients compared to control subjects, confirm the inflammatory link of upper and lower airways. The more frequent detection of inflammatory changes induced by ASNC in winter suggests that allergen exposure favours the transfer of nasal inflammation to lower airways.

Tubular aggregates: sarcoplasmic reticulum origin, calcium storage ability, and functional implications

Muscle biopsy specimens from three patients with an autosomal dominant myopathy and tubular aggregates in both type 1 and type 2 fibers were investigated for immunofluorescent staining with antibodies to sarcoplasmic reticulum (SR) Ca-pump protein and calsequestrin and for Ca2+ loading ability. The results show that type 1 and type 2 fibers are differentially reactive to anti-Ca-pump protein IgG and similarly reactive with affinity-purified antibody to calsequestrin, which is in agreement with earlier observations in rat skeletal muscle. Tubular aggregates, which are shown to be highly reactive with either kind of antibody, appear to be sites of calcium accumulation for oxalate-facilitated adenosine triphosphate (ATP) dependent Ca uptake by chemically skinned fibers and thereby increase markedly the Ca loading capacity of the affected fibers.

Decreased expression of DMPK: correlation with CTG repeat expansion and fibre type composition in myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is an autosomal dominant disease caused by a trinucleotide repeat-expansion, cytosine-thymine-guanine (CTG)n, in the 3' untranslated region of a gene encoding the myotonic dystrophy protein kinase (DMPK). To correlate CTG expansion and protein expression, we studied muscle specimens from 16 adult DM1 patients using three anti-DMPK antibodies for immunoblotting. We estimated the amount of the full-length DMPK (85 kDa) in muscle biopsies from normal controls and from DM1 patients carrying different (CTG)n expansions. We found that DMPK concentration was decreased to about 50% in DM patients' muscles; the protein decrease did not seem correlated with the CTG repeat length. However, the fibre type composition in skeletal muscle seemed somehow to affect DMPK decrease, as the lowest level of the enzyme was found in patients with the lowest content of type 1 fibre.

Three-year follow-up of clinical and inflammation parameters in children monosensitized to mites undergoing sub-lingual immunotherapy

Parallel follow-up of clinical and inflammatory markers during sub-lingual immunotherapy (SLIT) is highly beneficial. Twenty-four children (age 4-16) monosensitized to house dust mite were randomized to receive either active or placebo SLIT for 1 yr in a double-blind placebo controlled design (Marcucci et al., Allergy 2003: 58: 657-62). Thereafter, for 2 yr they all received active treatment. Symptom scores for rhinitis, asthma, and drug usage were daily recorded. Eosinophil cationic protein (ECP) and tryptase in sputum and nasal secretions, serum and nasal mite-specific immunoglobulin E (IgE) were recorded before treatment and at 10-12 months intervals. Nasal ECP and nasal tryptase after specific nasal provocation tests were significantly reduced as compared to baseline values (p = 0.0043 and 0.0195, respectively) in the third year of active treatment. None of the other inflammatory parameters was increased. In placebo treated patients all these parameters tended to decrease only after switching to active treatment. Clinical scores did not improve in treated vs. placebo patients in the double-blind placebo-controlled phase of the study. In both cohorts a clinical benefit was observed as intra-group score reduction as compared to baseline. A significant difference was reached in patients treated for 2 yr for rhinitis and asthma (p = 0.0009 and 0.0019, respectively) but not for drug usage and in patients treated for 3 yr for rhinitis, asthma, and drug usage (p = 0.0105, 0.0048, and 0.02, respectively). SLIT in children monosensitized to mites reverted the spontaneous increase in nasal IgE and in local parameters of allergic inflammation. These outcomes were followed by a consolidated clinical improvement in the second and third year of treatment.

Measurement of nasal IgE in an epidemiological study: assessment of its diagnostic value in respiratory allergy

BACKGROUND

Specific questionnaire and skin prick test (SPT) are the most used methods in epidemiological studies on respiratory allergy. SPT, however, can be positive in many subjects without evidence of any allergic disease. Nasal IgE determination has been suggested by some authors as a valuable diagnostic method, which may overcome this lack of specificity.

OBJECTIVE

The aim of this study was to evaluate sensitivity and specificity of nasal specific IgE for the seven most common inhalant allergens in order to verify its reliability as a screening test.

METHODS

126 children, involved in an epidemiological study on prevalence of respiratory allergic disease, were evaluated. All children were assessed with a specific questionnaire, SPT and nasal specific IgE. Nasal specific IgE were determined with a previously described method modified for screening purposes, in order to test seven allergens at the same time. When discordant results were obtained between questionnaire, SPT and nasal IgE, an allergen specific nasal challenge (ASNC) was performed and nasal tryptase was also determined before and after challenge.

RESULTS

The questionnaire was positive for respiratory allergy in 28/126 children. SPT was positive in 21 of the 28 children, but also in 5/10 children with atopic dermatitis (AD), and in 12/88 children without allergic symptoms. Nasal IgE were positive in 22/28 and also in 2/10 with AD. Nasal challenge and tryptase confirmed the negativity of nasal IgE in 12/17 children with positive SPT but totally negative for allergic respiratory disease. Moreover nasal IgE was found to be positive to dermatophagoides in one of seven children with negative SPT despite a clinical history suggestive for mite respiratory allergy. In this patient and in 2 of the 5 children with AD the positive nasal IgE to mites was confirmed by a positive ASNC and tryptase.

CONCLUSIONS

Nasal IgE have shown a specificity significantly higher than SPT (98% vs. 83%) and a good sensibility. This screening test may also be useful to detect the beginning of upper airways sensitization in patients with AD.

Evaluation of “Steroid-Sparing” Effects of Xanthena® Cream in Patients with Mild to Moderate Atopic Dermatitis

Emollients play an important role in the management of atopic dermatitis (AD). The aim of this study was to evaluate the efficacy and the “steroid-sparing” activity of an emollient cream (Xanthena® cream) in patients with mild to moderate AD. Patients were asked to apply twice a day for 7 days a cream containing hydrocortisone butyrate on the lesionai skin and then to apply Xanthena® cream only on the left side of affected areas. During the 2-month study period, the use of the corticosteroid cream was resumed in case of flare-up in any side.

The results obtained show significant differences of both the total severity score and the intensity of each symptom and sign of AD between the skin areas treated with Xanthena® cream and the control areas (P<0.05); a relevant reduction of steroid requirement was also noted in correlation with the use of this emollient cream (P<0.05). A significant improvement was observed even after the first month of therapy for most symptoms, except for excoriations/fissuring, oozing/crusting and burning which improved only at 2 months. Treatment was well-tolerated by the majority of patients; adverse local reactions, mostly transient and of mild intensity, were observed in 7% of cases.

Myotonic dystrophy protein kinase expressed in rat cardiac muscle is associated with sarcoplasmic reticulum and gap junctions

Myotonic dystrophy (DM) is one of the most prevalent muscular diseases in adults. The molecular basis of this autosomal disorder has been identified as the expansion of a CTG repeat in the 3' untranslated region of a gene encoding a protein kinase (DMPK). The pathophysiology of the disease and the role of DMPK are still obscure. It has been previously demonstrated that DMPK is localized at neuromuscular junctions, myotendinous junctions, and terminal cisternae of the sarcoplasmic reticulum (SR), in the skeletal muscle, and at intercalated discs in the cardiac muscle. We report here new findings about specific localization of DMPK in the heart. Polyclonal antibodies raised against a peptide sequence of the human DMPK were used to analyze the subcellular distribution of the protein in rat papillary muscles. Confocal laser microscopy revealed a strong although discontinuous reactivity at intercalated discs, together with transverse banding on the sarcoplasm. At higher resolution with immunogold electron microscopy, we observed that DMPK is localized at the cytoplasmic surface of junctional and extended junctional sarcoplasmic reticulum, suggesting that DMPK is involved in the regulation of excitation-contraction coupling. Along the intercalated disc, DMPK was found associated with gap junctions, whereas it was absent in the two other kinds of junctional complexes (fasciae adherentes and desmosomes). Immunogold labeling of gap junction purified fractions showed that DMPK co-localized with connexin 43, the major component of this type of intercellular junctions, suggesting that DMPK plays a regulatory role in the transmission of signals between myocytes.

Evidence for localization of the myotonic dystrophy protein kinase to the terminal cisternae of the sarcoplasmic reticulum

Myotonic dystrophy is an autosomal dominant multisystem disease primarily affecting skeletal muscle and is characterized by the presence of an amplified trinucleotide repeat in the 3' untranslated region of the myotonic dystrophy protein kinase gene. In this study, the subcellular localization of the myotonic dystrophy protein kinase in muscle tissues has been investigated at both morphological and biochemical level, by using antibodies against the myotonic dystrophy protein kinase. Immunofluorescence studies and Western-blot analysis were carried out with antibodies raised against both a synthetic peptide and a recombinant fusion protein fragment specific for the myotonic dystrophy protein kinase. The kinase is localized both to the surface membranes, and within the skeletal fibres in the region of the A-I band boundary. Consistent with the A-I location of the kinase is that Western-blot analysis of purified fractions from sarcoplasmic reticulum show that triads and sarcoplasmic reticulum terminal cisternae are immunoreactive for two myotonic dystrophy protein kinase proteins of different molecular weight (85 and 54 kDa). The relative amount of these two proteins is different in relation to the muscle type, the 85 kDa protein being more evident in skeletal than in cardiac fibres. In addition, immunofluorescence studies of cardiac muscle reveal a heavy concentration of DM-PK localized to the intercalated discs, as well as a weaker reaction in the sarcoplasm. These results taken together suggest that multiple isoforms of the DM-PK may exist and that they may be differentially located in muscle tissues.

Epidemiology of somatoform disorders: a community survey in Florence

Since the exclusion of somatic causes is necessary for somatoform disorders (SMD) to be diagnosed, there is little information on the prevalence of such disorders in the community. As the method we have previously developed [general practitioners (GPs) with psychiatric training who interview samples representative of the general population] seemed to be appropriate to deal with the problem, we carried out a community survey focused on somatoform disorders. The prevalence rates of DSM-III-R somatoform disorders were studied in two wards of the city of Florence. In order to be representative of the general population, 673 subjects randomly selected were interviewed by their own GP. Four GPs, all with specific training in psychiatry, participated in the interviewing process. The 1-year prevalence figures were as follows: 0.7% body dysmorphic disorder; 4.5% hypochondriasis; 0.6% somatoform pain disorder; 0.3% conversion disorder; 0.7% somatization disorder; 13.8% undifferentiated somatoform disorder. No specific comorbidity was found between somatoform disorders and mood or anxiety disorders. Although the sample investigated was small, this study may be seen as one of the first in an area where knowledge is still scant. The prevalence rates of somatoform disorders were generally found to be slightly lower than expected.

Identification and localization of the myotonic dystrophy gene product in skeletal and cardiac muscles

We have raised a polyclonal antibody against a synthetic peptide chosen within the deduced sequence of the myotonic dystrophy gene product. This antibody binds to a protein whose molecular weight is in the range of 50-54 kDa in Western blotting of rat, rabbit and human muscles. Biochemical studies seem to indicate that this protein is a peripheral component of sarcoplasmic reticulum as well as of plasma membrane.

Dual role of calsequestrin as substrate and inhibitor of casein kinase-1 and casein kinase-2

Calsequestrin from different muscle tissues and species has been phosphorylated by casein kinase-1 and casein kinase-2, in the conditions previously reported by Cala and Jones (J. Biol. Chem. 266, 391-398, 1991). Results indicates that rabbit cardiac and skeletal calsequestrin and frog skeletal calsequestrin are phosphorylated by both casein kinase-1 and casein kinase-2, at variance with chicken skeletal calsequestrin which is a poor substrate for both enzymes. We also observed that chicken calsequestrin is able to inhibit phosphorylation of cardiac calsequestrin, as well as other specific substrates, when added together to the assay medium.

Localization of protein kinase C in skeletal muscle T-tubule membranes

Membrane fractions enriched in transverse tubules, either predominantly free or junctional, sarcoplasmic reticulum subfractions and purified sarcolemmal preparations have been isolated from rabbit skeletal muscle and examined for their contents of protein kinase C. Using activity measurements and immunoblotting methods, we have been able to detect substantial amounts of endogenous protein kinase C in T-tubules membranes and to a lesser extent, in muscle sarcolemma. Protein kinase C was found to be highest in junctional T-tubules and to be virtually absent from sarcoplasmic reticulum-derived membrane fractions. Immunofluorescence staining of muscle fibers is consistent with a T-tubule localization of the kinase. The T-tubule-associated protein kinase C enzyme phosphorylates several potentially important membrane proteins.

Dystrophin is phosphorylated by endogenous protein kinases

Dystrophin, the protein coded by the gene missing in Duchenne muscular dystrophy, is assumed to be a component of the membrane cytoskeleton of skeletal muscle. Like other cytoskeletal proteins in different cell types, dystrophin bound to sarcolemma membranes was found to be phosphorylated by endogenous protein kinases. The phosphorylation of dystrophin was activated by cyclic AMP, cyclic GMP, calcium and calmodulin, and was inhibited by cyclic AMP-dependent protein kinase peptide inhibitor, mastoparan and heparin. These results suggest that membrane-bound dystrophin is a substrate of endogenous cyclic AMP- and cyclic GMP-dependent protein kinases, calcium/calmodulin-dependent kinase and casein kinase II. The possibility that dystrophin could be phosphorylated by protein kinase C is suggested by the inhibition of phosphorylation by staurosporin. On the other hand dystrophin seems not to be a substrate for protein tyrosine kinases, as shown by the lack of reaction of phosphorylated dystrophin with a monoclonal antiphosphotyrosine antibody. Sequence analysis indicates that dystrophin contains seven potential phosphorylation sites for cyclic AMP- and cyclic GMP-dependent protein kinases (all localized in the central rod domain of the molecule) as well as several sites for protein kinase C and casein kinase II. Interestingly, potential sites of phosphorylation by protein kinase C and casein kinase II are located in the proximity of the actin-binding site. These results suggest, by analogy with what has been demonstrated in the case of other cytoskeletal proteins, that the phosphorylation of dystrophin by endogenous protein kinases may modulate both self assembly and interaction of dystrophin with other cytoskeletal proteins in vivo.

Amino acid sequence of chicken calsequestrin deduced from cDNA: comparison of calsequestrin and aspartactin

We have previously reported the amino terminal sequence of adult chicken calsequestrin, an intraluminal Ca2(+)-binding protein isolated from fast-twitch skeletal muscle. The partial sequence showed homology with mammalian calsequestrins contained in the PIR data bank and complete identity with the amino terminus of a putative laminin-binding protein of the extracellular matrix, aspartactin. Based on these data, oligonucleotide primers were synthesized for PCR amplification and direct DNA sequencing. We report herein the primary sequence of chicken calsequestrin, deduced from cDNA. The sequence has been verified by amino acid sequencing of internal tryptic peptides. Importantly, the data show the primary structure of calsequestrin to be identical to the amino acid sequence reported for aspartactin, with the exception of a single amino acid difference (ileu vs. val) which may be animal strain-related. Based on these data, calsequestrin and aspartactin are the same protein.

Co-localization of the dihydropyridine receptor and the cyclic AMP-binding subunit of an intrinsic protein kinase to the junctional membrane of the transverse tubules of skeletal muscle

Junctional transverse tubules (TT) isolated from triads of rabbit skeletal muscle by centrifugation in an ion-free sucrose gradient were compared with membrane subfractions, predominantly derived from the free portion of TT, that had been purified from sarcoplasmic reticulum membrane contaminants by three different methods. The markers used were diagnostic membrane markers and the dihydropyridine (DHP) receptor, which is a specific marker of the junctional membrane of TT. Junctional TT have a high membrane density (Bmax. 60 pmol/mg of protein) of high-affinity (Kd 0.25 nM) DHP-binding sites using [3H]PN200-110 as the specific ligand. When analysed by SDS/PAGE under reducing conditions and by Western blot techniques, the TT were found to contain a concanavalin A-binding 150 kDa glycoprotein which probably corresponds to the alpha 2-subunit of the DHP receptor. This conclusion was supported by correlative immunoblot experiments with a specific antibody. Junctional TT are further distinguished from free TT by the presence of a high number (Bmax. 20 pmol/mg of protein) of [3H]cyclic AMP receptor sites, as determined by the Millipore filtration technique of Gill & Walton [(1974) Methods Enzymol. 38, 376-381]. Use of this method means that the number of receptors may have been underestimated. The TT-bound cyclic AMP receptor was identified as a 55 kDa protein by specific photoaffinity labelling with 8-N3-[3H]cyclic AMP, and had similar phosphorylation properties and apparent molecular mass to the RII form of the regulatory subunit of cyclic AMP-dependent protein kinase. Co-localization of the intrinsic cyclic AMP-dependent protein kinase and of the DHP receptor complex to the junctional membrane of TT supports the hypothesis that the 170 kDa alpha 1-subunit of the receptor is a substrate for the kinase.

Characterization of calsequestrin of avian skeletal muscle

A calsequentrin (CS)-like glycoprotein is present in the sarcoplasmic reticulum (SR) of chicken pectoralis muscle, which displays unusual properties: it binds relatively low amounts of Ca2+, compared to CS in mammalian skeletal muscle (Yap & MacLennan, 1976), it does not exhibit a marked pH-dependent shift in mobility in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), and its metachromatic staining properties with Stains All are likewise peculiar (Damiani et al., 1986). We have now definitively localized the same protein to the junctional terminal cisternae (TC) fraction of the SR of chicken pectoralis muscle and have further characterized it, following purification by crystallization with Ca2+ and by Ca2(+)-dependent elution from phenyl-Sepharose columns. The purified protein (apparent Mr: 51 kDa), isoelectrofocuses at pH 4.5, and is readily identified on blots by a 45Ca overlay technique, similar to CS of rabbit skeletal muscle, but it binds half as much Ca2+ (about 20 moles of Ca2+ per mole of protein), as estimated by equilibrium dialysis. However, the chicken protein shares extensive similarities with mammalian CSs, concerning Ca2(+)-induced changes in maximum intrinsic fluorescence and the Ca2(+)-modulated interaction with phenyl-Sepharose, as well as in being protected by Ca2+ from proteolysis by either trypsin or chymotrypsin. We discuss how the presence of a Ca2(+)-regulated hydrophobic site in the CS molecule appears to be the most invariant property of the CS-family of Ca2(+)-binding proteins.

Calsequestrin, an intracellular calcium-binding protein of skeletal muscle sarcoplasmic reticulum, is homologous to aspartactin, a putative laminin-binding protein of the extracellular matrix

Calsequestrin was isolated from chicken fast-twitch skeletal muscle, and partial amino terminal sequence was determined. The sequence (NH2) EEGLNFPTYDGKDRVIDLNE shows high identity with known mammalian calsequestrins contained in the Protein Identification Resource data bank (1). Most importantly, this 20 amino acid sequence shares complete identity with the amino terminus of aspartactin, a putative laminin-binding protein of the extracellular matrix (2, 3). The possible relationship of aspartactin to calsequestrin is discussed.

Characterization of high-capacity low-affinity calcium binding protein of liver endoplasmic reticulum: calsequestrin-like and divergent properties

It had been previously demonstrated that endoplasmic reticulum membranes from rat hepatocytes contain a major calsequestrin-like protein, on account of electrophoretic and Stains All-staining properties (Damiani et al., J. Biol. Chem. 263, 340-343). Here we show that a Ca2+-binding protein sharing characteristics in size and biochemical properties with this protein is likewise present in the isolated endoplasmic reticulum from human liver. Human calsequestrin-like protein was characterized as 62 kDa, highly acidic protein (pl 4.5), using an extraction procedure from whole tissue, followed by DEAE-Cellulose chromatography, that was originally developed for purification of skeletal muscle and cardiac calsequestrin. Liver calsequestrin-like protein bound Ca2+ at low affinity (Kd = 4 mM) and in high amounts (Bmax = 1600 nmol Ca2+/mg of protein), as determined by equilibrium dialysis, but differed strikingly from skeletal muscle calsequestrin for the lack of binding to phenyl-Sepharose resin in the absence of Ca2+, and of changes in intrinsic fluorescence upon binding of Ca2+. Thus, these results suggest that liver 62 kDa protein, in spite of its calsequestrin-like Ca2+-binding properties, does not contain a Ca2+-regulated hydrophobic site, which is a specific structural feature of the calsequestrin-class of Ca2+-binding proteins.

Denervation-induced proliferative changes of triads in rabbit skeletal muscle

Protein compositional and functional differences exist between longitudinal and junctional sarcoplasmic reticulum (SR) in relation to Ca transport and to Ca release. In light of this knowledge, we have reinvestigated the effects of denervation on SR of rabbit gastrocnemius, a predominantly fast muscle. Electron microscopy of 2-weeks denervated muscle showed proliferation of transverse tubules (TT), forming junctional contacts with SR terminal cisternae (TC). At coincident periods, the yield of muscle microsomes was increased, and their fractionation by sucrose-density centrifugation demonstrated a relative increase of heavy vesicles. Thin-section electron microscopy of heavy SR from denervated muscle showed an increased number of vesicles containing calsequestrin (CS) as compared with control muscle. Electrophoretic analysis confirmed the relative decrease of Ca-ATPase protein and the striking increase of CS both in total microsomes and in heavy SR vesicles. Calcium loading and Ca-ATPase activity as well as the density of Ca-ATPase protein were decreased to a similar extent (20-30%) in denervated muscle microsomes. Stimulation of Ca-ATPase activity by Ca-ionophore A23187 showed that the vesicles were tightly sealed. When probed by competitive ELISA with antibody to SR Ca-ATPase from pure fast muscle, the Ca-ATPase of denervated microsomes was found to be highly cross reactive. Cleveland's peptide maps of the Ca-ATPase protein after partial digestion with S. aureus V8 protease also showed no significant change after denervation. Changes in cholesterol content and in the ratio of Mg-ATPase to Ca-ATPase activity of denervated muscle microsomes indicated a 4-fold increase of TT protein, i.e., from about 3% to not more than 12% of total protein, at 2 weeks after denervation. All these changes were totally reversed upon reinnervation of muscle fibers, and the consequent muscle recovery, as obtained by nerve crushing instead of nerve sectioning. From these results, we conclude that denervated adult fast muscle, similarly to immature fast muscle, contains more junctional SR. However, the molecular and catalytic properties of the Ca-ATPase are unaffected by denervation.

Endoplasmic reticulum of rat liver contains two proteins closely related to skeletal sarcoplasmic reticulum Ca-ATPase and calsequestrin

Rat liver endoplasmic reticulum (ER) membranes were investigated for the presence of proteins having structural relationships with sarcoplasmic reticulum (SR) proteins. Western immunoblots of ER proteins probed with polyclonal antibodies raised against the 100-kDa SR Ca-ATPase of rabbit skeletal muscle identified a single reactive protein of 100 kDa. Also, the antibody inhibited up to 50% the Ca-ATPase activity of isolated ER membranes. Antisera raised against the major intraluminal calcium binding protein of rabbit skeletal muscle SR, calsequestrin (CS), cross-reacted with an ER peptide of about 63 kDa, by the blotting technique. Stains-All treatment of slab gels showed that the cross-reactive peptide stained metachromatically blue, similarly to SR CS. Two-dimensional electrophoresis (Michalak, M., Campbell, K. P., and MacLennan, D. H. (1980) J. Biol. Chem. 255, 1317-1326) of ER proteins showed that the CS-like component of liver ER, similarly to skeletal CS, fell off the diagonal line, as expected from the characteristic pH dependence of the rate of mobility of mammalian CS. In addition, the CS-like component of liver ER was released from the vesicles by alkaline treatment and was found to be able to bind calcium, by a 45Ca overlay technique. From these findings, we conclude that a 100-kDa membrane protein of liver ER is the Ca-ATPase, and that the peripheral protein in the 63-kDa range is closely structurally and functionally related to skeletal CS.

Characteristics of skeletal muscle calsequestrin: comparison of mammalian, amphibian and avian muscles

Calsequestrin was identified in the isolated sarcoplasmic reticulum from skeletal muscle of three mammalian species (man, rat and rabbit) and from frog and chicken muscle, using electrophoretic and immunoblot techniques. It was further characterized in sarcoplasmic reticulum protein mixtures and at several stages of purification, following extraction with EDTA. We found extensive similarities in apparent molecular weight values, Stains All staining properties and in Cleveland's peptide maps, between mammalian calsequestrins, and no detectable difference within a species between fast and slow muscle. Human calsequestrin, with an apparent molecular weight of 60,000 when measured at alkaline pH and of 41,000 when measured at neutral pH, appears to be the smallest in size. Frog calsequestrin, although weakly cross-reactive with rabbit calsequestrin and having a relatively higher apparent molecular weight at alkaline pH (72,000), shares several significant properties with mammalian calsequestrins. It bound calcium with a high capacity (1300 nmol per mg protein), it contained about 32% acidic amino acid residues and focused at closely similar pI values. We observed the formation of a complex with Stains All absorbing maximally at 535 nm, rather than at 600 nm, and an even more marked shift in apparent molecular weight at neutral pH. We found distinct differences in the case of chicken calsequestrin, in addition to those previously reported. It is a highly acidic, calcium-precipitable protein, but its amino acid composition is contradistinguished by a higher ratio of glutamate to aspartate and its rate of electrophoretic mobility is minimally affected by changes in pH. It stained deep bluish with Stains All after gel electrophoresis and yielded a protein-dye complex in aqueous solution, absorbing maximally at 560 nm, and finally, it bound fluorescent Concanavalin A.

Biochemical heterogeneity of skeletal-muscle microsomal membranes. Membrane origin, membrane specificity and fibre types

1. Microsomes were isolated from rabbit fast-twitch and slow-twitch muscle and were separated into heavy and light fractions by centrifugation in a linear (0.3-2m) sucrose density gradient. The membrane origin of microsomal vesicles was investigated by studying biochemical markers of the sarcoplasmic-reticulum membranes and of surface and T-tubular membranes, as well as their freeze-fracture properties. 2. Polyacrylamide-gel electrophoresis showed differences in the Ca(2+)-dependent ATPase/calsequestrin ratio between heavy and light fractions, which were apparently consistent with their respective origin from cisternal and longitudinal sarcoplasmic reticulum, as well as unrelated differences, such as peptides specific to slow-muscle microsomes (mol.wts. 76000, 60000, 56000 and 45000). 3. Freeze-fracture electron microscopy of muscle microsomes demonstrated that vesicles truly derived from the sarcoplasmic reticulum, with an average density of 9nm particles on the concave face of about 3000/mum(2) for both fast and slow muscle, were admixed with vesicles with particle densities below 1000/mum(2). 4. As determined in the light fractions, the sarcoplasmic-reticulum vesicles accounted for 84% and 57% of the total number of microsomal vesicles, for fast and slow muscle respectively. These values agreed closely with the percentage values of Ca(2+)-dependent ATPase protein obtained by gel densitometry. 5. The T-tubular origin of vesicles with a smooth concave fracture face in slow-muscle microsomes is supported by their relative high content in total phospholipid and cholesterol, compared with the microsomes of fast muscle, and by other correlative data, such as the presence of (Na(+)+K(+))-dependent ATPase activity and of low amounts of Na(+)-dependent membrane phosphorylation. 6. Among intrinsic sarcoplasmic-reticulum membrane proteins, a proteolipid of mol.wt. 12000 is shown to be identical in the microsomes of both fast and slow muscle and the Ca(2+)-dependent ATPase to be antigenically and catalytically different, though electrophoretically homogeneous. 7. Basal Mg(2+)-activated ATPase activity was found to be high in light microsomes from slow muscle, but its identification with an enzyme different from the Ca(2+)-dependent ATPase is still not conclusive. 8. Enzyme proteins that are suggested to be specific to slow-muscle longitudinal sarcoplasmic reticulum are the flavoprotein NADH:cytochrome b(5) reductase (mol.wt. 32000), cytochrome b(5) (mol.wt. 17000) and the stearoyl-CoA desaturase, though essentially by criteria of plausibility.