The actin-myosin regulatory MRCK kinases: regulation, biological functions and associations with human cancer

The contractile actin-myosin cytoskeleton provides much of the force required for numerous cellular activities such as motility, adhesion, cytokinesis and changes in morphology. Key elements that respond to various signal pathways are the myosin II regulatory light chains (MLC), which participate in actin-myosin contraction by modulating the ATPase activity and consequent contractile force generation mediated by myosin heavy chain heads. Considerable effort has focussed on the role of MLC kinases, and yet the contributions of the myotonic dystrophy-related Cdc42-binding kinases (MRCK) proteins in MLC phosphorylation and cytoskeleton regulation have not been well characterized. In contrast to the closely related ROCK1 and ROCK2 kinases that are regulated by the RhoA and RhoC GTPases, there is relatively little information about the CDC42-regulated MRCKα, MRCKβ and MRCKγ members of the AGC (PKA, PKG and PKC) kinase family. As well as differences in upstream activation pathways, MRCK and ROCK kinases apparently differ in the way that they spatially regulate MLC phosphorylation, which ultimately affects their influence on the organization and dynamics of the actin-myosin cytoskeleton. In this review, we will summarize the MRCK protein structures, expression patterns, small molecule inhibitors, biological functions and associations with human diseases such as cancer

miR147b : A novel key regulator of interleukin 1 beta-mediated inflammation in human astrocytes

Astrocytes are important mediators of inflammatory processes in the brain and seem to play an important role in several neurological disorders, including epilepsy. Recent studies show that astrocytes produce several microRNAs, which may function as crucial regulators of inflammatory pathways and could be used as therapeutic target. We aim to study which miRNAs are produced by astrocytes during IL-1β mediated inflammatory conditions in vitro, as well as their functional role and to validate these findings in human epileptogenic brain tissue. Sequencing was used to assess miRNA and mRNA expression in IL-1β-stimulated human fetal astrocyte cultures. miRNAs were overexpressed in cell cultures using miRNA mimics. Expression of miRNAs in resected brain tissue from patients with tuberous sclerosis complex or temporal lobe epilepsy with hippocampal sclerosis was examined using in situ hybridization. Two differentially expressed miRNAs were found: miR146a and miR147b, which were associated with increased expression of genes related to the immune/inflammatory response. As previously reported for miR146a, overexpression of miR147b reduced the expression of the pro-inflammatory mediators IL-6 and COX-2 after IL-1β stimulation in both astrocyte and tuberous sclerosis complex cell cultures. miR146a and miR147b overexpression decreased proliferation of astrocytes and promoted neuronal differentiation of human neural stem cells. Similarly to previous evidence for miR146a, miR147b was increased expressed in astrocytes in epileptogenic brain. Due to their anti-inflammatory effects, ability to restore aberrant astrocytic proliferation and promote neuronal differentiation, miR146a and miR147b deserve further investigation as potential therapeutic targets in neurological disorders associated with inflammation, such as epilepsy

Circadian clock component REV-ERBα controls homeostatic regulation of pulmonary inflammation

Recent studies reveal that airway epithelial cells are critical pulmonary circadian pacemaker cells, mediating rhythmic inflammatory responses. Using mouse models, we now identify the rhythmic circadian repressor REV-ERBα as essential to the mechanism coupling the pulmonary clock to innate immunity, involving both myeloid and bronchial epithelial cells in temporal gating and determining amplitude of response to inhaled endotoxin. Dual mutation of REV-ERBα and its paralog REV-ERBβ in bronchial epithelia further augmented inflammatory responses and chemokine activation, but also initiated a basal inflammatory state, revealing a critical homeostatic role for REV-ERB proteins in the suppression of the endogenous proinflammatory mechanism in unchallenged cells. However, REV-ERBα plays the dominant role, as deletion of REV-ERBβ alone had no impact on inflammatory responses. In turn, inflammatory challenges cause striking changes in stability and degradation of REV-ERBα protein, driven by SUMOylation and ubiquitination. We developed a novel selective oxazole-based inverse agonist of REV-ERB, which protects REV-ERBα protein from degradation, and used this to reveal how proinflammatory cytokines trigger rapid degradation of REV-ERBα in the elaboration of an inflammatory response. Thus, dynamic changes in stability of REV-ERBα protein couple the core clock to innate immunity

Circadian clock component REV-ERBα controls homeostatic regulation of pulmonary inflammation

Recent studies reveal that airway epithelial cells are critical pulmonary circadian pacemaker cells, mediating rhythmic inflammatory responses. Using mouse models, we now identify the rhythmic circadian repressor REV-ERBα as essential to the mechanism coupling the pulmonary clock to innate immunity, involving both myeloid and bronchial epithelial cells in temporal gating and determining amplitude of response to inhaled endotoxin. Dual mutation of REV-ERBα and its paralog REV-ERBβ in bronchial epithelia further augmented inflammatory responses and chemokine activation, but also initiated a basal inflammatory state, revealing a critical homeostatic role for REV-ERB proteins in the suppression of the endogenous proinflammatory mechanism in unchallenged cells. However, REV-ERBα plays the dominant role, as deletion of REV-ERBβ alone had no impact on inflammatory responses. In turn, inflammatory challenges cause striking changes in stability and degradation of REV-ERBα protein, driven by SUMOylation and ubiquitination. We developed a novel selective oxazole-based inverse agonist of REV-ERB, which protects REV-ERBα protein from degradation, and used this to reveal how proinflammatory cytokines trigger rapid degradation of REV-ERBα in the elaboration of an inflammatory response. Thus, dynamic changes in stability of REV-ERBα protein couple the core clock to innate immunity

Treinamento de natação na intensidade do limiar anaeróbio melhora a aptidão funcional de ratos idosos Swimming training at anaerobic threshold intensity improves the functional fitness of older rats

Os efeitos do treinamento aeróbio em intensidade relativa ao limiar de lactato (LL) foram analisados em 15 ratos idosos (~448 dias de vida). Os grupos de animais treinados (n=9) e controle (n=6) foram submetidos a um teste antes e após quatro semanas de treinamento. O teste incremental consistiu de uma carga inicial de 1% do peso corporal e incrementos de 1% a cada três minutos, com mensurações de lactato sanguíneo para identificação do LL por inspeção visual do ponto de inflexão da curva. O programa de treinamento consistiu de 30 minutos de natação/dia, cinco dias/semana, com sobrecarga de 5% do peso corporal (PC), ou controle sem exercício. Foi observado aumento significativo na intensidade do LL após o treinamento (pré = 4,5 ± 1,1 vs. Pós = 5.4 ± 0.9% PC). A carga máxima atingida ao final do teste incremental aumentou significativamente de 39,7 ± 7,5g no pré para 48,4 ± 10,5g no pós treinamento, sem mudanças para o grupo controle (44,7 ± 8 vs. 45,3 ± 9,3g). O peso corporal do grupo treinado não apresentou diferença como resultado de quatro semanas de natação em intensidade correspondente ao LL (641,0 ±62,0 para 636,0 ± 72.7g; p>0.05). Por outro lado, o grupo não treinado aumentou significativamente o PC de 614,0 ± 8,0 para 643,0 ± 74,1g. A carga máxima atingida expressa tanto em valores absolutos como relativos (%PC) aumentou significativamente após o treinamento. Conclui-se que quatro semanas de treinamento de natação em intensidade correspondente ao limiar de lactato resultou em uma melhora da aptidão aeróbia e na manutenção do peso corporal em ratos idosos.<br>The effects of aerobic training at the lactate threshold (LT) intensity were analyzed in fifteen older rats (~448 days old). Both the trained (n = 9) and control (n = 6) groups were submitted to an incremental exercise test before and after four weeks of training. The incremental exercise test consisted of an initial load of 1% BM and 1% increments at each 3-min with blood lactate measurements. The LT was determined by visual inspection of the blood lactate breakpoint. The training program comprised of 30-min swimming/day, 5 days/week, loaded with 5% body mass (BM), or control without exercise. Significant increase on the LT intensity after training (pre = 4.5 ± 1.1 vs. post = 5.4 ± 0.9% BM). The maximal workload reached at the end of incremental test increased significantly from 39.7 ± 7.5 g on pre to 48.4 ± 10.5 g at post training, with no changes for the control group (44.7 ± 8 vs. 45.3 ± 9.3 g). The body mass of the trained group did not change as a result of 4 weeks of swimming at LT intensity (641.0 ± 62.0 to 636.0 ± 72.7 g; p > 0.05). On the other hand, the untrained group increased significantly the BM from 614.0 ± 80.0 to 643.0 ± 72.7 g. The maximal workload, as expressed both in relation to absolute and relative values (i.e. %BM) increased significantly only as a result of training. It was concluded that four weeks of swimming training at LT intensity resulted in aerobic fitness improvement and body mass maintenance of older rats

Fish oil normalizes plasma glucose levels and improves liver carbohydrate metabolism in rats fed a sucrose-rich diet

A sucrose-rich diet (SRD) induces insulin resistance and dyslipidemia with impaired hepatic glucose production and gluconeogenesis, accompanied by altered post-receptor insulin signaling steps. The aim of this study was to examine the effectiveness of fish oil (FO) to reverse or improve the impaired hepatic glucose metabolism once installed in rats fed 8 months a SRD. In the liver of rats fed SRD in which FO replaced corn-oil during the last 2 months, as dietary fat, several key enzyme activities and metabolites involved in glucose metabolisms (phosphorylation, glycolysis, gluconeogenesis and oxidative and non oxidative glucose pathway) were measured. The protein mass levels of IRS-1 and ap85 PI-3K at basal conditions were also analyzed. FO improved the altered activities of some enzymes involved in the glycolytic and oxidative pathways observed in the liver of SRD fed rats but was unable to restore the impaired capacity of glucose phosphorylation. Moreover, FO reversed the increase in PEPCK and G-6-Pase and reduced the G-6-Pase/GK ratio. Glycogen concentration and GSa activity returned to levels similar to those observed in the liver of the control-fed rats. Besides, FO did not modify the altered protein mass levels of IRS-1 and αp85 PI-3K. Finally, dietary FO was effective in reversing or improving the impaired activities of several key enzymes of hepatic carbohydrate metabolism contributing, at least in part, to the normalization of plasma glucose levels in the SRD-fed rats. However, these positive effects of FO were not observed under basal conditions in the early steps of insulin signaling transduction. © 2011 AOCS.Fil: Hein, Gustavo Juan. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; ArgentinaFil: Chicco, Adriana Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; ArgentinaFil: Lombardo, Yolanda B.. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentin