Nuclear factor-kappaB (NF-kappaB) is a major transcription factor that plays an essential role in several aspects of human health including the development of innate and adaptive immunity. The dysregulation of NF-kappaB is associated with many disease states such as AIDS, atherosclerosis, asthma, arthritis, cancer, diabetes, inflammatory bowel disease, muscular dystrophy, stroke, and viral infections. Recent evidence also suggests that the dysfunction of NF-kappaB is a major mediator of some human genetic disorders. Appropriate regulation and control of NF-kappaB activity, which can be achieved by gene modification or pharmacological strategies, would provide a potential approach for the management of NF-kappaB related human diseases. This review summarizes the current knowledge of the physiological and pathophysiological functions of NF-kappaB and its possible role as a target of therapeutic intervention

The ex vivo effects of passive mechanical stretch on the activation of nuclear factor-kappaB (NF-kappaB) pathways in skeletal muscles from normal and mdx mouse, a model of Duchenne muscular dystrophy (DMD), were investigated. The NF-kappaB/DNA binding activity of the diaphragm muscle was increased by the application of axial mechanical stretch in a time-dependent manner. The increased activation of NF-kappaB was associated with a concomitant increase in I-kappaB (IkappaB) kinase activity and the degradation of IkappaBalpha protein. Pretreatment of the muscles with nifedipine (a Ca2+ channel blocker) and gadolinium(III) chloride (a stretch-activated channel blocker) did not alter the level of activation of NF-kappaB, ruling out involvement of Ca2+ influx through these channels. Furthermore, N-acetyl cysteine, a free radical inhibitor, blocked the mechanical stretch-induced NF-kappaB activation, suggesting the involvement of free radicals. Compared with normal diaphragm, the basal level of NF-kappaB activity was higher in muscles from mdx mice, and it was further enhanced in mechanically stretched muscles. Furthermore, activation of NF-kappaB and increased expression of inflammatory cytokines IL-1beta and tumor necrosis factor alpha in the mdx mouse precede the onset of muscular dystrophy. Our results show that mechanical stretch activates the classical NF-kappaB pathway and this pathway could be predominately active in DMD.

Rationale: The small conducting airways are the major site of airflow obstruction in chronic obstructive pulmonary disease and may precede emphysema development.Objectives: We hypothesized a novel computed tomography (CT) biomarker of small airway disease predicts FEV 1 decline.Methods: We analyzed 1,508 current and former smokers from COPDGene with linear regression to assess predictors of change in FEV 1 (ml/yr) over 5 years. Separate models for subjects without and with airflow obstruction were generated using baseline clinical and physiologic predictors in addition to two novel CT metrics created by parametric response mapping (PRM), a technique pairing inspiratory and expiratory CT images to define emphysema (PRM emph ) and functional small airways disease (PRM fSAD ), a measure of nonemphysematous air trapping.Measurements and Main Results: Mean (SD) rate of FEV 1 decline in ml/yr for GOLD (Global Initiative for Chronic Obstructive Lung Disease) 0-4 was as follows: 41.8 (47.7), 53.8 (57.1), 45.6 (61.1), 31.6 (43.6), and 5.1 (35.8), respectively (trend test for grades 1-4; P , 0.001). In multivariable linear regression, for participants without airflow obstruction, PRM fSAD but not PRM emph was associated with FEV 1 decline (P , 0.001). In GOLD 1-4 participants, both PRM fSAD and PRM emph were associated with FEV 1 decline (P , 0.001 and P = 0.001, respectively). Based on the model, the proportional contribution of the two CT metrics to FEV 1 decline, relative to each other, was 87% versus 13% and 68% versus 32% for PRM fSAD and PRM emph in GOLD 1/2 and 3/4, respectively.Conclusions: CT-assessed functional small airway disease and emphysema are associated with FEV 1 decline, but the association with functional small airway disease has greatest importance in mildto-moderate stage chronic obstructive pulmonary disease where the rate of FEV 1 decline is the greatest.Clinical trial registered with www.clinicaltrials.gov (NCT 00608764).

Airway smooth muscle hypertrophy is one of the hallmarks of airway remodeling in severe asthma. Several human diseases have been now associated with dysregulated microRNA (miRNA) expression. miRNAs are a class of small non-coding RNAs, which negatively regulate gene expression at the post-transcriptional level. Here, we identify miR-26a as a hypertrophic miRNA of human airway smooth muscle cells (HASMCs). We show that stretch selectively induces the transcription of miR-26a located in the locus 3p21.3 of human chromosome 3. The transcription factor CCAAT enhancer-binding protein ␣ (C/EBP␣) directly activates miR-26a expression through the transcriptional machinery upon stretch. Furthermore, stretch or enforced expression of miR-26a induces HASMC hypertrophy, and miR-26 knockdown reverses this effect, suggesting that miR-26a is a hypertrophic gene. We identify glycogen synthase kinase-3␤ (GSK-3␤), an anti-hypertrophic protein, as a target gene of miR-26a. Luciferase reporter assays demonstrate that miR-26a directly interact with the 3-untranslated repeat of the GSK-3␤ mRNA. Stretch or enforced expression of miR-26a attenuates the endogenous GSK-3␤ protein levels followed by the induction of HASMC hypertrophy. miR-26 knockdown reverses this effect, suggesting that miR-26a-induced hypertrophy occurs via its target gene GSK-3␤. Overall, as a first time, our study unveils that miR-26a is a mechanosensitive gene, and it plays an important role in the regulation of HASMC hypertrophy. MicroRNAs (miRNAs)2 are an evolutionarily conserved novel class of small non-coding RNAs that have achieved status as potent regulators of gene expression. According to their genomic location relative to protein-coding gene locus, miRNAs can be divided into intergenic miRNAs and intragenic miRNAs. The former have independent transcriptional units, including promoter, transcript sequence, and terminator; therefore, they do not overlap with other genes (1, 2). The later are found in the introns of protein-coding host genes, and they generally share the same regulatory motifs with their host genes (3-5). Most of the miRNAs are transcribed by RNA polymerase II as primary miRNAs (1, 2) and processed by the RNase III enzymes Drosha and Dicer to produce 21-to 23-nucleotide double-stranded RNA duplexes (6, 7). These smaller RNAs are then exported to the cytoplasm by Exportin 5 (8, 9), where they are subsequently processed into mature miRNAs by Dicer. The mature miRNAs are loaded into the miRNA-induced silencing complex (7), where they recognize their target protein-coding mRNAs to inhibit mostly mRNA translation or degradation (10) by base pairing to complementary sequences within the 3Ј-untranslated region (3Ј UTR). With respect to miRNAs functions, they play pivotal roles in the pathophysiological processes such as apoptosis, cell differentiation, cell proliferation, and organ development (4, 11). Functionally speaking, several human diseases have now been associated with dysregulated miRNAs expression.Airway remodeling is a characteristic featu...

Dystrophin is a cytoskeletal protein found at the inner surface of skeletal and cardiac muscle fibers. We hypothesize that deficiency of dystrophin increases muscle compliance and causes an aberrant mechanotransduction in muscle fibers. To test this hypothesis, we measured the length-tension relationships and determined intracellular signaling leading to the activation of mitogen-activated protein (MAP) kinases in diaphragm muscle fibers from dystrophin-deficient mdx mice. Compared with controls, length-tension curves of the mdx mice were shifted to the right. A higher level of activation of extracellular signal-regulated kinase 1/2 (ERK1/2) but not c-Jun N-terminal kinase-1 or p38 MAP kinase was observed in the mdx muscle compared with the normal muscle in response to mechanical stretch. Removal of Ca2+ from the medium inhibited stretch-induced ERK1/2 activation only in mdx muscle fibers but not in the normal fibers. Conversely, pretreatment with TMB-8 (an antagonist of intracellular Ca2+ blocked the mechanical stretch-induced ERK1/2 activation in normal but not in mdx muscle fibers. Pretreatment of muscle with nifedipine (L-type calcium channel antagonist) marginally decreased the activation of ERK1/2 in normal or mdx muscle whereas pretreatment with gadolinium (III) chloride (an inhibitor of stretch-activated channels) only blocked the activation of ERK1/2 in mdx muscle, with no significant effect on normal muscle. A higher basal level of activation of activator protein-1 (AP-1) transcription factor was observed in dystrophin-deficient diaphragm, which was further augmented by mechanical stretch. Mechanical stretch-induced activation of AP-1 was decreased by pretreatment of muscle fibers with PD98059 (ERK1/2 inhibitor) and removal of Ca2+ ions from incubation medium. Our results show that dystrophin is a load-bearing element and its deficiency leads to loss of muscle stiffness and aberrant mechanotransduction in skeletal muscle fibers.

High-fat diet (HFD) plays a central role in the initiation of mitochondrial dysfunction that significantly contributes to skeletal muscle metabolic disorders in obesity. However, the mechanism by which HFD weakens skeletal muscle metabolism by altering mitochondrial function and biogenesis is unknown. Given the emerging roles of microRNAs (miRNAs) in the regulation of skeletal muscle metabolism, we sought to determine whether activation of a specific miRNA pathway would rescue the HFD-induced mitochondrial dysfunction via the sirtuin-1 (SIRT-1)/ peroxisome proliferator–activated receptor γ coactivator-1α (PGC-1α) pathway, a pathway that governs genes necessary for mitochondrial function. We here report that miR-149 strongly controls SIRT-1 expression and activity. Interestingly, miR-149 inhibits poly(ADP-ribose) polymerase-2 (PARP-2) and so increased cellular NAD+ levels and SIRT-1 activity that subsequently increases mitochondrial function and biogenesis via PGC-1α activation. In addition, skeletal muscles from HFD-fed obese mice exhibit low levels of miR-149 and high levels of PARP-2, and they show reduced mitochondrial function and biogenesis due to a decreased activation of the SIRT-1/PGC-1α pathway, suggesting that mitochondrial dysfunction in the skeletal muscle of obese mice may be because of, at least in part, miR-149 dysregulation. Overall, miR-149 may be therapeutically useful for treating HFD-induced skeletal muscle metabolic disorders in such pathophysiological conditions as obesity and type 2 diabetes.

In the diaphragm muscle we tested the hypothesis that MAP kinase signaling pathways are activated by mechanical stress and such signaling pathways are dependent on the direction in which mechanical stress is applied. Although equal magnitudes of mechanical stress were applied axially and transversely a greater level of activation of ERK1/2, p38, Raf-1, p90 RSK, Elk-1, and the DNA binding activity of AP-1 transcription factor was produced when the muscle was stretched transversely than when stretched axially. A significant up-regulation in protein tyrosine phosphorylation was observed in axially or transversely loaded diaphragm muscles and the activation of ERK1/2 was completely inhibited by genistein (protein-tyrosine kinase inhibitor). Pretreatment of muscles with wortmannin (phosphoinositide 3-kinase inhibitor), TMB-8 (antagonist of intracellular calcium release), GF109203X (PKC inhibitor), or PD98059 (MEK1/2 inhibitor) blocked the activation of ERK1/2 kinases in response to axial but not to transverse loading. On the other hand, pretreatment of muscles with protein kinase A inhibitors H-7 and KT5720 completely suppressed the activation of ERK1/2 in response to transverse loading only. Taken together with the alterations of MAP kinases and the findings of elevations of downstream transcription targets, our data are consistent with two distinct MAP kinase signal transduction pathways in response to mechanical stress.

This article examines the mechanics of the muscles that drive expansion or contraction of the chest wall during breathing. The diaphragm is the main inspiratory muscle. When its muscle fibers are activated in isolation, they shorten, the dome of the diaphragm descends, pleural pressure (P(pl)) falls, and abdominal pressure (P(ab)) rises. As a result, the ventral abdominal wall expands, but a large fraction of the rib cage contracts. Expansion of the rib cage during inspiration is produced by the external intercostals in the dorsal portion of the rostral interspaces, the intercartilaginous portion of the internal intercostals (the so-called parasternal intercostals), and, in humans, the scalenes. By elevating the ribs and causing an additional fall in P(pl), these muscles not only help the diaphragm expand the chest wall and the lung, but they also increase the load on the diaphragm and reduce the shortening of the diaphragmatic muscle fibers. The capacity of the diaphragm to generate pressure is therefore enhanced. In contrast, during expiratory efforts, activation of the abdominal muscles produces a rise in P(ab) that leads to a cranial displacement of the diaphragm into the pleural cavity and a rise in P(pl). Concomitant activation of the internal interosseous intercostals in the caudal interspaces and the triangularis sterni during such efforts contracts the rib cage and helps the abdominal muscles deflate the lung.