Adhesion in skeletal muscle during regeneration.

Adhesion molecules were studied in regenerating skeletal muscle immunohistochemically and ultrastructurally after a standardized trauma. In normal muscle, extracellular matrix (ECM) protein tenascin was restricted to myotendinous junctions (MTJ), while the integrin beta 1-subunit was present also on the sarcolemma. After injury, tenascin increased on the outer surface of regenerating myofibers, where cellular fibronectin also accumulated. Later, tenascin concentrated at the tips of regenerating myofibers, where new MTJs were formed. The beta 1-subunit disappeared on necrotized myofibers and reappeared on regenerating fibers in a thicker layer. The regenerating myofibers were invested by a basal lamina, except for the growth cones at the distal ends, which were laminin-negative until the formation of MTJs occurred. These results indicate that regenerating muscle cells are attached to the ECM in a way that allows both growth of the muscle cells across the scar and their use before the regeneration is completed.     

Epistatic effects of genes encoding immunoglobulin GM allotypes and interleukin-6 on the production of autoantibodies to 60- and 65-kDa heat-shock proteins

Immunoglobulin GM and KM genes have been associated with antibody responses to a variety of antigens. A promoter-region polymorphism of interleukin-6 (IL-6) gene (-174 G/C) has been shown to be associated with antibody responses to heat-shock proteins (hsp) 60 and hsp65. To examine the possible epistatic effects of these unlinked genetic systems on the autoimmune responses to hsp60 and hsp65, 176 healthy Caucasian subjects from Finland were genotyped for several allelic determinants of GM, KM, and IL-6 genes by PCR-RFLP methods. IgG antibodies to hsp60 and hsp65 were measured by an ELISA. Significant interactive effects of GM f,z and IL-6-174 genotypes were noted for both anti-hsp60 (P=0.002) and anti-hsp65 (P=0.038) antibody levels. Since these autoantibodies have been implicated in susceptibility to coronary heart disease and carotid atherosclerosis, the associations reported here might be relevant to the etiology of these diseases.     

Mechanisms dependent on tryptophan catabolism regulate immune responses in primary Sjögren's syndrome

To investigate the possible role of tryptophan metabolism in immune regulation of primary Sjögren's syndrome (pSS) the serum concentrations of tryptophan and its metabolite kynurenine were measured by reverse‐phase high‐performance liquid chromatography (HPLC) in 103 patients with pSS, 56 patients with sicca symptoms and 309 healthy blood donors. The kynurenine per tryptophan ratio (kyn/trp), which reflects the activity of the indoleamine‐pyrrole 2,3‐dioxygenase (IDO) enzyme involved in tryptophan catabolism, was calculated. Both female and male patients with pSS had significantly higher serum kynurenine concentrations and kyn/trp than subjects with sicca symptoms or healthy blood donors. The median (quartile range) concentration of kynurenine in female patients with pSS was 2·41 µmol/l (1·86–3·26) compared with 1·85 µmol/l (1·58–2·38, P < 0·0001) in subjects with sicca symptoms and 1·96 µmol/l (1·65–2·27, P < 0·0001) in healthy blood donors. Their kyn/trp × 1000 was 34·0 (25·1–44·3) compared with 25·3 (21·1–31·5, P < 0·0001) in subjects with sicca symptoms and 24·3 (21·0–28·9, P < 0·0001) in healthy blood donors. Female pSS patients with high IDO activity (kyn/trp × 1000 ≥ 34·0) had significantly higher ESR, serum C‐reactive protein, serum IgA and serum beta‐2 microglobulin concentrations as well as higher serum creatinine levels, and they had positive antinuclear antibodies more frequently and presented with more American‐European consensus group criteria than those with low IDO activity (kyn/trp × 1000 < 34·0). These data suggest that mechanisms dependent on tryptophan catabolism regulate immune responses in pSS. Tryptophan degradation is enhanced in patients with pSS, and high IDO activity is associated with severity of pSS.     

The effect of cyclophosphamide on cytotoxic T-lymphocyte responses: inhibition of helper T-cell induction in vitro.

The effects of cyclophosphamide (Cy) on the different cell populations participating in the cytotoxic T lymphocyte (CTL) response against haptenated (trinitrophenyl, TNP) syngeneic cells were studied. Pretreatment of responder cell donor mice with 150 mg/kg Cy decreased the cytotoxicity against TNP-modified syngeneic target cells almost to the background level. When TH cells were added to the culture the cytotoxicity increased significantly. Helper T cells were generated in vivo by priming the mice with TNP-modified syngeneic spleen cells or sensitizing the mice with a reactive hapten (TNCB). However, if the TH cell donor mice were treated with Cy before in vivo priming, the cytotoxicity reached the normal level, which indicated that TH precursors were not destroyed by Cy treatment and TH induction was even more effective after Cy. These data indicate that the decrease of the response by this Cy dose is not due to the sensitivity of CTL or TH precursors. Mice could be primed with male-specific (HY) antigen in spite of Cy pretreatment. However, Cy pretreatment caused a latent period of 2 weeks when effective CTL could not be generated in vitro, but after that the capacity for CTL generation was restored. These experiments confirm that pretreatment of responder cell donor mice with Cy does not destroy CTL or TH precursors, but rather affects their in vitro restimulation probably by destroying a short lived 'inducer' cell that is needed.     

Specific and innervation-regulated expression of the intermediate filament protein nestin at neuromuscular and myotendinous junctions in skeletal muscle

The intermediate filament proteins nestin, vimentin, and desmin show a specific temporal expression pattern during the development of myofibers from myogenic precursor cells. Nestin and vimentin are actively expressed during early developmental stages to be later down-regulated, vimentin completely and nestin to minimal levels, whereas desmin expression begins later and is maintained in mature myofibers, in which desmin participates in maintaining structural integrity. In this study we have analyzed the expression levels and distribution pattern of nestin in intact and denervated muscle in rat and in human. Nestin immunoreactivity was specifically and focally localized in the sarcoplasm underneath neuromuscular junctions (NMJs) and in the vicinity of the myotendinous junctions (MTJs), ie, in regions associated with acetylcholine receptors (AChRs). This association prompted us to analyze nestin in neurogenically and myogenically denervated muscle. Immunoblot analysis disclosed a marked overall increase of accumulated nestin protein. Similar to the extrajunctional redistribution of AChRs in denervated myofibers, nestin immunoreactivity extended widely beyond the NMJ region. Re-innervation caused complete reversion of these changes. Our study demonstrates that the expression levels and distribution pattern of nestin are regulated by innervation, ie, signal transduction into myofibers.     

Meta-analysis of epigenome-wide association studies of carotid intima-media thickness

Common carotid intima-media thickness (cIMT) is an index of subclinical atherosclerosis that is associated with ischemic stroke and coronary artery disease (CAD). We undertook a cross-sectional epigenome-wide association study (EWAS) of measures of cIMT in 6400 individuals. Mendelian randomization analysis was applied to investigate the potential causal role of DNA methylation in the link between atherosclerotic cardiovascular risk factors and cIMT or clinical cardiovascular disease. The CpG site cg05575921 was associated with cIMT (beta?=??0.0264, p value?=?3.5?×?10^–8) in the discovery panel and was replicated in replication panel (beta?=??0.07, p value?=?0.005). This CpG is located at chr5:81649347 in the intron 3 of the aryl hydrocarbon receptor repressor gene (AHRR). Our results indicate that DNA methylation at cg05575921 might be in the pathway between smoking, cIMT and stroke. Moreover, in a region-based analysis, 34 differentially methylated regions (DMRs) were identified of which a DMR upstream of ALOX12 showed the strongest association with cIMT (p value?=?1.4?×?10^–13). In conclusion, our study suggests that DNA methylation may play a role in the link between cardiovascular risk factors, cIMT and clinical cardiovascular disease.

     

Genetics of inflammation and atopy

Multiple chromosomal regions and polymorphisms of several candidate genes have been linked to or associated with atopic diseases (hayfever, asthma, allergic eczema and rhinitis). In this mini-review, we present data demonstrating that the genetic regulation of the inflammatory response makes a major contribution to the risk of atopy. These data also suggest that the quantity (or quality) of the inflammation affects the priming phase of atopy, i.e., that induced by allergens or infectious agents in early childhood.     

The caries-preventive effect of xylitol/maltitol and erythritol/maltitol lozenges: results of a double-blinded, cluster-randomized clinical trial in an area of natural fluoridation

International Journal of Paediatric Dentistry 2012; 22: 180–190 Objective. Xylitol studies suggest caries reductions in the order of 50%. Based on animal/microbial studies, erythritol potentially has caries‐preventive properties. However, clinical studies are required to confirm this.The aim of the study was to investigate the additional caries‐preventive effect of xylitol/maltitol and erythritol/maltitol lozenges delivered at school, relative to controls receiving comprehensive prevention, in a low‐caries prevalence population. Methods. A 4‐year, cluster‐randomized, double‐blinded clinical trial. Five hundred and seventy‐nine 10‐year‐old consenting subjects from 21 schools were randomly assigned to one of five groups. Four groups used the lozenges on school days, in three teacher‐supervised sessions daily, over 1 or 2 years. The daily amount was 4.7 g/4.6 g for xylitol/maltitol and 4.5 g/4.2 g for erythritol/maltitol. The groups received free examinations and care in the public health centre. Four hundred and ninety‐six children were analysed. The main outcome measure was dentin caries increment based on a clinical examination at 4 years since the start. The groups were compared in relation to the increment using hierarchical logistic regression to adjust for potential clustering. Results. Use of xylitol/maltitol or erythritol/maltitol lozenges did not result in caries reduction. A strong relationship between baseline caries prevalence and the 4‐year increment was observed (OR = 7.38; 95% CI: 3.78–14.41). Conclusions. The results suggest that in relatively low‐caries conditions the school‐based use of xylitol/maltitol or erythritol/maltitol lozenges would not have additional caries‐preventive effect when compared with comprehensive prevention.