miR-15b is Downregulated in Myasthenia Gravis Patients and Directly Regulates the Expression of Interleukin-15 (IL-15) in Experimental Myasthenia Gravis Mice.

BACKGROUND: miR-15b is significantly and consistently downregulated in different clinical phenotypes of myasthenia gravis (MG). However, its role in pathogenesis of MG is still not clear. This study aimed to explore the function of miR-15b in MG. MATERIAL AND METHODS: Blood samples from early-onset MG, late-onset MG, thymoma patients, and healthy participants were collected. The expression pattern of IL-15 and miR-15b was identified by qRT-PCR and ELISA in patient serum and mouse tissue samples. The regulative role of miR-15b on IL-15 expression was verified in an experimental autoimmune myasthenia gravis (EAMG) mice model. RESULTS: qRT-PCR and ELISA showed that miR-15b expression was significantly lower and IL-15 expression was significantly higher in all EMG, LMG, and thymoma cases compared to healthy controls. Based on mouse model, we confirmed that miR-15b knockdown could increase IL-15 expression in healthy mice, while miR-15b overexpression could inhibit IL-15 expression in EAMG mice. Through searching in bioinformatics databases, we identified a highly conserved consequential pairing between IL-15 and miR-15b. Subsequent dual luciferase assay further verified this match. CONCLUSIONS: This study is the first to report the miR-15b-IL-15 axis can directly regulate IL15 expression, which helps to further explain the abnormal IL-15 expression in MG patients and the pathogenesis of MG.

Age­ and brain region­associated alterations of cerebral blood flow in early Alzheimer's disease assessed in AßPPSWE/PS1ΔE9 transgenic mice using arterial spin labeling.

It has been suggested that cerebral blood flow (CBF) alterations may be involved in the pathogenesis of Alzheimer's disease (AD). However, how CBF changes with age has not been detailed in AD, particularly in its early stages. The objective of the present study was to evaluate CBF in four brain regions (the hippocampus, entorhinal cortex, frontoparietal cortex and thalamus) of mice in four age groups, to mimic the respective stages of AD in humans [2 months (pre­clinical), 3.5 months (sub­clinical), 5 months (early­clinical) and 8 months (mid­clinical)], to understand the age­associated changes in selected brain regions and to elucidate the underlying vascular mechanisms. CBF was measured using magnetic resonance imaging­arterial spin labelling (ASL) under identical conditions across the age groups of AßPPSWE/PS1ΔE9 (APP/PS1) transgenic mice with AD. The results indicated age­ and brain region­associated changes in CBF were associated with early AD. More precisely, an age­dependent increase in CBF (in the pre­ and sub­clinical AD groups) was observed in the frontoparietal cortex and thalamus. Conversely, increased CBF demonstrated an age­dependent decline (in the early­ and mid­clinical AD groups) in all examined brain regions. Among the regions, the thalamus had the greatest increase in CBF in the 2 and 3.5 months age groups, which was substantially different compared with the age­matched controls. An extension of vessel area was also noted to be age­ and brain region­dependent. In particular, correlation analysis revealed significant associations of CBF with vessel area in the frontoparietal cortex and thalamus of APP/PS1 mice at ages 2 and 3.5 months, indicating that CBF increase may arise from vessel extension. The results of the present study suggested that ASL can detect age­ and brain region­associated changes in CBF in mice with AD, and that ASL­measured CBF increase may be a potential diagnostic biomarker for early AD. The observation that CBF increase resulted from vessel extension may aid in the understanding of the vascular role in age­associated development of AD pathology, and provide preclinical evidence for AD patient management.

Expression of the genes encoding kinin receptors are increased in human carotid atherosclerotic plaques.

There is increasing evidence showing that inflammation occurs in atherosclerosis and contributes to the formation of atherosclerotic plaques. As important inflammatory peptides, kinins are increased in inflammation, eliciting vasodilation, increasing vascular permeability and recruiting inflammatory cells to the injury sites by activating specific receptors, B1 and B2. The two receptors have been reported to increase in inflammation, but their expressions remain to be defined in human carotid atherosclerotic plaques (CAP). In order to assess the gene expression of kinin receptors in human CAP, 47 CAP specimens were collected from patients undergoing endarterectomy and classified into stable and unstable plaque groups, respectively, with 10 mesenteric arteries used as controls. Total mRNA of B1R and B2R was extracted from CAPs and their levels were determined using reverse transcription-polymerase chain reaction. The expression of B1R and B2R mRNA was significantly upregulated in human CAPs compared to the control arteries. In the unstable plaques, the ratios of B1R to the ß-actin mRNA level were significantly increased relative to the stable plaques. However, no notable differences were observed in the ratios of B2R to ß-actin in mRNA expression between the stable and unstable plaques. The present study suggests that kinin-mediated inflammation involves the formation of atherosclerotic plaque and B1R plays an important role in plaque instability, indicating that kinin receptors can be used as potential targets for future therapeutic interventions.

Determination of the normative values of the masseter muscle by single-fiber electromyography in myasthenia gravis patients.

The purpose of this study is to obtain normative values of the masseter muscle of myasthenia gravis (MG) patients and healthy volunteers by single-fiber electromyography (SFEMG). Stimulation of SFEMG in the masseter muscle was studied in 15 healthy volunteers (men 8, women 7; mean age 40.2, range 21-77) and 30 patients affected by MG (men 16, women 14; mean age 42.8, range 12-75). The mean consecutive difference (MCD) of the individual fiber and the mean MCD per study were determined in the normal group. We recommend the upper normal limit for the individual fibers of jitter and the mean MCD per study in the healthy Chinese adults of 33 µs and 22 µs respectively. Furthermore, in the MG group, the percentage of jitter > upper normal limit jitter and the impulse blocking percentage were detected, which were all significantly different compared to the normal control group (P < 0.01). The overall sensitivity was 90%, with the abnormality in 6 of the 9 ocular MG patients and 100% abnormality in the generalized MG patients. The masseter muscle SFEMG has a high degree of sensitivity. The masseter should be considered for SFEMG in the diagnosis of MG, and added routinely to the tested muscles.

Significance of ABCA1 in human carotid atherosclerotic plaques.

The ATP-binding cassette transporter A1 (ABCA1) is an important effector in the regulation of cholesterol efflux from cells. In this study, we assessed the role of ABCA1 in human carotid atherosclerotic plaques (CAPs). We found that ABCA1 and retinoid X receptor α (RXRα) mRNAs were significantly increased in the atherosclerotic plaques compared to control arteries. The increased ABCA1 mRNA correlated with that of RXRα in plaques. According to the modified American Heart Association plaque classification, atherosclerotic specimens were assigned to three grades, and ABCA1 and RXRα mRNA levels were compared across plaques of different grades. Resultantly, plaques of grade II and III exhibited higher mRNA levels than grade I, but there was no difference in mRNA levels between plaques of grade II and III. By contrast, ABCA1 and RXRα protein levels were notably reduced in plaques relative to control tissues. Similarly, plaques of grade II and III exhibited lower ABCA1 and RXRα protein levels than grade I, and there was no difference in protein levels between plaques of grade II and III. Our findings suggest that decreased ABCA1 protein plays a key role in the pathogenesis of CAP; the regulation of ABCA1 may be mediated by RXRα and ABCA1 mRNA levels may serve as an indicator for plaque stability.