Neuronal Nitric Oxide Synthase-Rescue of Dystrophin/Utrophin Double Knockout Mice does not Require nNOS Localization to the Cell Membrane

Survival of dystrophin/utrophin double-knockout (dko) mice was increased by muscle-specific expression of a neuronal nitric oxide synthase (nNOS) transgene. Dko mice expressing the transgene (nNOS TG+/dko) experienced delayed onset of mortality and increased life-span. The nNOS TG+/dko mice demonstrated a significant decrease in the concentration of CD163+, M2c macrophages that can express arginase and promote fibrosis. The decrease in M2c macrophages was associated with a significant reduction in fibrosis of heart, diaphragm and hindlimb muscles of nNOS TG+/dko mice. The nNOS transgene had no effect on the concentration of cytolytic, CD68+, M1 macrophages. Accordingly, we did not observe any change in the extent of muscle fiber lysis in the nNOS TG+/dko mice. These findings show that nNOS/NO (nitric oxide)-mediated decreases in M2c macrophages lead to a reduction in the muscle fibrosis that is associated with increased mortality in mice lacking dystrophin and utrophin. Interestingly, the dramatic and beneficial effects of the nNOS transgene were not attributable to localization of nNOS protein at the cell membrane. We did not detect any nNOS protein at the sarcolemma in nNOS TG+/dko muscles. This important observation shows that sarcolemmal localization is not necessary for nNOS to have beneficial effects in dystrophic tissue and the presence of nNOS in the cytosol of dystrophic muscle fibers can ameliorate the pathology and most importantly, significantly increase life-span

Rs895819 in MIR27A improves the predictive value of DPYD variants to identify patients at risk of severe fluoropyrimidine-associated toxicity

The objective of this study was to determine whether genotyping of MIR27A polymorphisms rs895819A>G and rs11671784C>T can be used to improve the predictive value of DPYD variants to identify patients at risk of severe fluoropyrimidine-associated toxicity (FP-toxicity). Patients treated previously in a prospective study with fluoropyrimidine-based chemotherapy were genotyped for rs895819 and rs11671784, and DPYD c.2846A>T, c.1679T>G, c.1129-5923C>G, and c.1601G>A. The predictive value of MIR27A variants for early-onset grade ≥3 FP-toxicity, alone or in combination with DPYD variants, was tested in multivariable logistic regression models. Random-effects meta-analysis was performed, including previously published data. 1592 patients were included. Allele frequencies of rs895819 and rs11671784 were 0.331 and 0.020, respectively. In DPYD wild type patients, MIR27A variants did not affect risk of FP-toxicity (OR 1.3 for ≥1 variant MIR27A allele vs. none, 95%CI 0.87-1.82, p=0.228). In contrast, in patients carrying DPYD variants, the presence of ≥1 rs895819 variant allele was associated with increased risk of FP-toxicity (OR 4.9, 95%CI 1.24-19.7, p=0.023). Rs11671784 was not associated with FP-toxicity (OR 2.9, p=0.253). Patients carrying a DPYD variant and rs895819 were at increased risk of FP-toxicity compared to patients wild type for rs895819 and DPYD (OR 2.4, 95%CI 1.27-4.37, p=0.007), while patients with a DPYD variant but without a MIR27A variant were not (OR 0.4, 95%CI 0.09-1.82, p=0.236). In meta-analysis, rs895819 remained significantly associated with FP-toxicity in DPYD variant allele carriers, OR 5.4 (95%CI 1.83-15.7, p=0.002). This study demonstrates the clinical validity of combined MIR27A/DPYD screening to identify patients at risk of severe FP-toxicity. This article is protected by copyright. All rights reserved