Unheralded Adrenergic Receptor Signaling in Cellular Oxidative Stress and Death.

Catecholamines (CAs) bind and activate adrenergic receptors (ARs), thus exuding a key role in cardiac adaptations to global physiological queues. Prolonged exposure to high levels of CAs promotes deleterious effects on the cardiovascular system, leading to organ dysfunction and heart failure (HF). In addition to the prominent role of ARs in inotropic and chronotropic responses, recent studies have delved into elucidating mechanisms contributing to CA toxicity and cell death. Central to this process is understanding the involvement of α1AR and ßAR in cardiac remodeling and mechanisms of cellular survival. Here, we highlight the complexity of AR signaling and the fundamental need for a better understanding of its contribution to oxidative stress and cell death. This crucial informational nexus remains a barrier to the development of new therapeutic strategies for cardiovascular diseases.

NOX4-TIM23 interaction regulates NOX4 mitochondrial import and metabolic reprogramming.

Pulmonary fibrosis is a progressive lung disease characterized by macrophage activation. Asbestos-induced expression of nicotinamide adenine dinucleotide phosphate hydrogen oxidase 4 (NOX4) in lung macrophages mediates fibrotic progression by the generation of mitochondrial reactive oxygen species (ROS), modulating mitochondrial biogenesis, and promoting apoptosis resistance; however, the mechanism(s) by which NOX4 localizes to mitochondria during fibrosis is not known. Here, we show that NOX4 localized to the mitochondrial matrix following asbestos exposure in lung macrophages via direct interaction with TIM23. TIM23 and NOX4 interaction was found in lung macrophages from human subjects with asbestosis, while it was absent in mice harboring a conditional deletion of NOX4 in lung macrophages. This interaction was localized to the proximal transmembrane region of NOX4. Mechanistically, TIM23 augmented NOX4-induced mitochondrial ROS and metabolic reprogramming to oxidative phosphorylation. Silencing TIM23 decreased mitochondrial ROS and oxidative phosphorylation. These observations highlight the important role of the mitochondrial translocase TIM23 interaction with NOX4. Moreover, this interaction is required for mitochondrial redox signaling and metabolic reprogramming in lung macrophages.

Aging, Plasminogen Activator Inhibitor 1, Brain Cell Senescence, and Alzheimer's Disease.

The etiology for late-onset Alzheimer's disease (LOAD), which accounts for >95% of Alzheimer's disease (AD) cases, is unknown. Emerging evidence suggests that cellular senescence contributes importantly to AD pathophysiology, although the mechanisms underlying brain cell senescence and by which senescent cells promote neuro-pathophysiology remain unclear. In this study we show for the first time that the expression of plasminogen activator inhibitor 1 (PAI-1), a serine protease inhibitor, is increased, in correlation with the increased expression of cell cycle repressors p53 and p21, in the hippocampus/cortex of senescence accelerated mouse prone 8 (SAMP8) mice and LOAD patients. Double immunostaining results show that astrocytes in the brain of LOAD patients and SAMP8 mice express higher levels of senescent markers and PAI-1, compared to astrocytes in the corresponding controls. In vitro studies further show that overexpression of PAI-1 alone, intracellularly or extracellularly, induced senescence, whereas inhibition or silencing PAI-1 attenuated H2O2-induced senescence, in primary mouse and human astrocytes. Treatment with the conditional medium (CM) from senescent astrocytes induced neuron apoptosis. Importantly, the PAI-1 deficient CM from senescent astrocytes that overexpress a secretion deficient PAI-1 (sdPAI-1) has significantly reduced effect on neurons, compared to the PAI-1 containing CM from senescent astrocytes overexpressing wild type PAI-1 (wtPAI-1), although sdPAI-1 and wtPAI-1 induce similar degree of astrocyte senescence. Together, our results suggest that increased PAI-1, intracellularly or extracellularly, may contribute to brain cell senescence in LOAD and that senescent astrocytes can induce neuron apoptosis through secreting pathologically active molecules, including PAI-1.

Mitochondrial fission and bioenergetics mediate human lung fibroblast durotaxis.

Pulmonary fibrosis is characterized by stiffening of the extracellular matrix. Fibroblasts migrate in the direction of greater stiffness, a phenomenon termed durotaxis. The mechanically guided fibroblast migration could be a crucial step in the progression of lung fibrosis. In this study, we found primary human lung fibroblasts sense increasing matrix stiffness with a change of mitochondrial dynamics in favor of mitochondrial fission and increased production of ATP. Mitochondria polarize in the direction of a physiologically relevant stiffness gradient, with conspicuous localization to the leading edge, primarily lamellipodia and filopodia, of migrating lung fibroblasts. Matrix stiffness-regulated mitochondrial fission and durotactic lung fibroblast migration are mediated by a dynamin-related protein 1/mitochondrial fission factor-dependent (DRP1/MFF-dependent) pathway. Importantly, we found that the DRP1/MFF pathway is activated in fibrotic lung myofibroblasts in both human IPF and bleomycin-induced mouse lung fibrosis. These findings suggest that energy-producing mitochondria need to be sectioned via fission and repositioned in durotactic lung fibroblasts to meet the higher energy demand. This represents a potentially new mechanism through which mitochondria may contribute to the progression of fibrotic lung diseases. Inhibition of durotactic migration of lung fibroblasts may play an important role in preventing the progression of human idiopathic pulmonary fibrosis.

MicroRNA expression profiling identifies molecular signatures associated with anaplastic large cell lymphoma.

Anaplastic large-cell lymphomas (ALCLs) encompass at least 2 systemic diseases distinguished by the presence or absence of anaplastic lymphoma kinase (ALK) expression. We performed genome-wide microRNA (miRNA) profiling on 33 ALK-positive (ALK[+]) ALCLs, 25 ALK-negative (ALK[-]) ALCLs, 9 angioimmunoblastic T-cell lymphomas, 11 peripheral T-cell lymphomas not otherwise specified (PTCLNOS), and normal T cells, and demonstrated that ALCLs express many of the miRNAs that are highly expressed in normal T cells with the prominent exception of miR-146a. Unsupervised hierarchical clustering demonstrated distinct clustering of ALCL, PTCL-NOS, and the AITL subtype of PTCL. Cases of ALK(+) ALCL and ALK(-) ALCL were interspersed in unsupervised analysis, suggesting a close relationship at the molecular level. We identified an miRNA signature of 7 miRNAs (5 upregulated: miR-512-3p, miR-886-5p, miR-886-3p, miR-708, miR-135b; 2 downregulated: miR-146a, miR-155) significantly associated with ALK(+) ALCL cases. In addition, we derived an 11-miRNA signature (4 upregulated: miR-210, miR-197, miR-191, miR-512-3p; 7 downregulated: miR-451, miR-146a, miR-22, miR-455-3p, miR-455-5p, miR-143, miR-494) that differentiates ALK(-) ALCL from other PTCLs. Our in vitro studies identified a set of 32 miRNAs associated with ALK expression. Of these, the miR-17∼92 cluster and its paralogues were also highly expressed in ALK(+) ALCL and may represent important downstream effectors of the ALK oncogenic pathway.

The role of Akt on arsenic trioxide suppression of 3T3-L1 preadipocyte differentiation.

The present study investigates the molecular details of how arsenic trioxide inhibits preadipocyte differentiation and examines the role of Akt/PKB in regulation of differentiation and apoptosis. Continual exposure of arsenic trioxide, at the clinic achievable dosage that does not induce apoptosis, suppressed 3T3-L1 cell differentiation into fat cells by inhibiting the expression of PPARgamma and C/EBPalpha and disrupting the interaction between PPARgamma and RXRalpha, which determines the programming of the adipogenic genes. Interestingly, if we treated the cells for 12 or 24 h and then withdrew arsenic trioxide, the cells were able to differentiate to the comparable levels of untreated cells as assayed by the activity of GAPDH, the biochemical marker of preadipocyte differentiation. Long term treatment blocked the differentiation and the activity of GAPDH could not recover to the comparable levels of untreated cells. Continual exposure of arsenic trioxide caused accumulation in G2/M phase and the accumulation of p21. We found that arsenic trioxide induced the expression and the phosphorylation of Akt/PKB and it inhibited the interaction between Akt/PKB and PPARgamma . Akt/PKB inhibitor appears to block the arsenic trioxide suppression of differentiation. Our results suggested that Akt/PKB may play a role in suppression of apoptosis and negatively regulate preadipocyte differentiation.

[Human hyperplasic suppress gene (hHSG) could increase the chemotherapy sensitivity of human tumor cells in vitro].

OBJECTIVE: To investigate whether the hHSG can increase the chemotherapy sensitivity of two human tumor cell lines,lung cancer cell line (A549) and cervical cancer cell line (HeLa S3), in which the hHSG expression levels are different. METHODS: After detecting the hHSG expression in different tumor cell lines with immunohistochemistry; we selected the A549 with relatively low expression of hHSG and HeLa S3 with high expression. After these two cell lines were transfected with recombinant eukaryotic expression vector of pEGFP-hHSG and pEGFP by electroporation respectively,and cultured for 24 h, the CHX was added to the medium, and the impacts of hHSG on chemotherapy sensitivity were evaluated by cell counting and MTT assay in the following days. RESULTS: hHSG expressed at different levels in all investigated tumor cell lines. Exogenetic hHSG inhibited the proliferation of tumor cell lines, and increased their sensitivity for CHX significantly. CONCLUSION: hHSG gene can inhibit the proliferation of tumor cells and increase their chemotherapy sensitivity despite of its endogenetic expression levels.

Cadmium directly induced the opening of membrane permeability pore of mitochondria which possibly involved in cadmium-triggered apoptosis.

The mitochondrial damage induced by cadmium has been well established, but its mechanism and its relationship with cadmium-induced apoptosis are elusive until now. Our research showed that cadmium could directly lead to the dysfunction of isolated mitochondria from mouse liver, including the inhibition of respiration, the opening of permeability transition pore (PTP), the loss of transmembrane potential, and the release of cytochrome c. These mitochondrial changes were completely suppressed by Bcl-xL and Ruthenium Red (RR). Bongkrekic acid (BK), an inhibitor of the PTP opening directly via adenine nucleotide translocator (ANT), also completely inhibited the PTP opening and loss of transmembrane potential. However, cyclosporin A (CsA), another inhibitor of the PTP opening indirectly via ANT, had not any inhibitory effect. When cadmium being pre-incubated with proteins containing abundant thiol groups, its effect was partially reversed. These results revealed that mitochondria pathway may involve in cadmium-induced apoptosis, and cadmium caused the PTP opening possibly through its binding to thiol groups of ANT. Furthermore, the mechanism of the PTP opening induced by cadmium was probably distinct from that of the calcium-induced PTP opening.