Characterization of an Acute Muscle Contraction Model Using Cultured C2C12 Myotubes

A cultured C2C12 myotube contraction system was examined for application as a model for acute contraction-induced phenotypes of skeletal muscle. C2C12 myotubes seeded into 4-well rectangular plates were placed in a contraction system equipped with a carbon electrode at each end. The myotubes were stimulated with electric pulses of 50 V at 1 Hz for 3 ms at 997-ms intervals. Approximately 80% of the myotubes were observed to contract microscopically, and the contractions lasted for at least 3 h with electrical stimulation. Calcium ion $(Ca^{2+})$ transient evoked by the electric pulses was detected fluorescently with Fluo-8. Phosphorylation of protein kinase B/Akt (Akt), 5′ AMP-activated protein kinase (AMPK), p38 mitogen-activated protein kinase (p38), and c-Jun NH2-terminal kinase (JNK)1/2, which are intracellular signaling proteins typically activated in exercised/contracted skeletal muscle, was observed in the electrically stimulated C2C12 myotubes. The contractions induced by the electric pulses increased glucose uptake and depleted glycogen in the C2C12 myotubes. C2C12 myotubes that differentiated after exogenous gene transfection by a lipofection or an electroporation method retained their normal contractile ability by electrical stimulation. These findings show that our C2C12 cell contraction system reproduces the muscle phenotypes that arise in vivo (exercise), in situ (hindlimb muscles in an anesthetized animal), and in vitro (dissected muscle tissues in incubation buffer) by acute muscle contraction, demonstrating that the system is applicable for the analysis of intracellular events evoked by acute muscle contraction

Variants of C-C Motif Chemokine 22 (CCL22) Are Associated with Susceptibility to Atopic Dermatitis: Case-Control Studies

Atopic dermatitis (AD) is a common inflammatory skin disease caused by multiple genetic and environmental factors. AD is characterized by the local infiltration of T helper type 2 (Th2) cells. Recent clinical studies have shown important roles of the Th2 chemokines, CCL22 and CCL17 in the pathogenesis of AD. To investigate whether polymorphisms of the CCL22 gene affect the susceptibility to AD, we conducted association studies and functional studies of the related variants. We first resequenced the CCL22 gene and found a total of 39 SNPs. We selected seven tag SNPs in the CCL22 gene, and conducted association studies using two independent Japanese populations (1st population, 916 cases and 1,032 controls; 2nd population 1,034 cases and 1,004 controls). After the association results were combined by inverse variance method, we observed a significant association at rs4359426 (meta-analysis, combined P = 9.6×10−6; OR, 0.74; 95% CI, 0.65–0.85). Functional analysis revealed that the risk allele of rs4359426 contributed to higher expression levels of CCL22 mRNA. We further examined the allelic differences in the binding of nuclear proteins by electrophoretic mobility shift assay. The signal intensity of the DNA-protein complex derived from the G allele of rs223821, which was in absolute LD with rs4359426, was higher than that from the A allele. Although further functional analyses are needed, it is likely that related variants play a role in susceptibility to AD in a gain-of-function manner. Our findings provide a new insight into the etiology and pathogenesis of AD

ORAI1 Genetic Polymorphisms Associated with the Susceptibility of Atopic Dermatitis in Japanese and Taiwanese Populations

Atopic dermatitis is a chronic inflammatory skin disease. Multiple genetic and environmental factors are thought to be responsible for susceptibility to AD. In this study, we collected 2,478 DNA samples including 209 AD patients and 729 control subjects from Taiwanese population and 513 AD patients and 1027 control subject from Japanese population for sequencing and genotyping ORAI1. A total of 14 genetic variants including 3 novel single-nucleotide polymorphisms (SNPs) in the ORAI1 gene were identified. Our results indicated that a non-synonymous SNP (rs3741596, Ser218Gly) associated with the susceptibility of AD in the Japanese population but not in the Taiwanese population. However, there is another SNP of ORAI1 (rs3741595) associated with the risk of AD in the Taiwanese population but not in the Japanese population. Taken together, our results indicated that genetic polymorphisms of ORAI1 are very likely to be involved in the susceptibility of AD

The New Role of Disodium Cromoglycate in the Treatment of Adults with Bronchial Asthma

Background: Viral infection of the respiratory tract in patients with asthma is one of the most frequent causes of exacerbation of asthmatic symptoms. Disodium cromoglycate (DSCG) is a commonly used anti-asthmatic medicine with many beneficial biochemical and physiological effects. The purpose of this study was to investigate the efficacy of DSCG against colds when used in clinical practice. Methods: A questionnaire survey to determine the efficacy of DSCG was undertaken in 220 adult patients with asthma (81 male, 139 female; mean age: 54.1 ± 13.7 years and 60.1 ± 12.7 years, respectively) from April to September 2004 at the Miyatake Asthma Clinic. Results: The duration of DSCG inhalation therapy was not less than 5 years in more than half of the patients. The mean daily DSCG dose at the time of the questionnaire survey was 40 mg/day in over 50% of all patients. After DSCG was added to inhaled corticosteroid (ICS) combination therapy, 56.4% of the patients rated their condition as “improved”, and 66.4% of the patients felt that the frequency of colds they had caught had decreased while DSCG was added to ICS. Conclusions: DSCG inhalation therapy is a useful additional treatment following ICS to alleviate asthma symptoms, and to prevent colds in adult patients with asthma

Ca²⁺ fluorescence with and without electrical stimulation.

<p>(A) Ca²⁺ fluorescence with and without electrical stimulation. Myotubes were treated with Fluo-8 dye loading solution 30 min before electrical stimulation. The images are shown at 200× magnification. The upper panel shows the bright-field image. The middle panel shows the myotubes with electric pulses, and the lower panel shows the myotubes without electric pulses. (B) Changes in Ca²⁺ fluorescence intensity with electrical stimulation. The fluorescence intensity was analyzed at 5 arbitrary points. Each line shows the raw fluorescence intensity data at each point. (C) The average fluorescence intensity for 11 s is shown. The average fluorescence intensity with electric pulses is significantly higher than that without electric pulses (<i>p</i><0.01, Student’s t-test).</p

Immunoblotting of phosphoproteins after electrical stimulation for 1 h.

<p>C2C12 myotubes were stimulated with electric pulses (50 V, 1 Hz, 3 ms) for 60 min at 37°C. Representative blots of the phosphorylation of Akt (Ser 308), p-38 (Thr180/Tyr182), AMPK (Thr172), and JNK1/2 (Thr183/Tyr185) and their expression levels induced by electrical stimulation for 60 min in C2C12 myotubes are shown. The phosphorylation ratios were calculated by dividing the phosphorylation levels by the protein expression levels. Significant increases in phosphorylated Akt (Ser 308), AMPK (Thr172), p-38 (Thr180/Tyr182), and JNK1/2 (Thr183/Tyr185) were detected after 1 h of contraction. Data are shown as mean ± S.E.M, n = 6–14.</p

LDH activity in the culture medium after 1 h of contraction in C2C12 myotubes.

<p>C2C12 myotubes were stimulated by electric pulses (50 V, 1 Hz, 3 ms) for 1 hr. There was no significant difference between non-contracted control and the contraction group (n = 6). LDH release (%) was calculated by dividing the amount of LDH in medium by the total amount of LDH in the medium and lysate (Materials and Methods).</p