For centuries, the black seed (Nigella sativa) herb and oil have been used in Asia, Middle East and Africa to promote health and fight disease. Thymoquinone (TQ), the most abundant constituent present in black seed, is a promising dietary chemopreventive agent. We investigated the effects of thymoquinone (TQ) against HCT-116 human colon cancer cells and attempted to identify its potential molecular mechanisms of action. We report that TQ inhibits the growth of colon cancer cells which was correlated with G1 phase arrest of the cell cycle. Furthermore, TUNEL staining and flow cytometry analysis indicate that TQ triggers apoptosis in a dose- and time-dependent manner. Apoptosis induction by TQ was associated with a 2.5-4.5-fold increase in mRNA expression of p53 and the downstream p53 target gene, p21WAF1. Simultaneously, we found a marked increase in p53 and p21WAF1 protein levels but a significant inhibition of anti-apoptotic Bcl-2 protein. Co-incubation with pifithrin-alpha (PFT-alpha), a specific inhibitor of p53, restored Bcl-2, p53 and p21WAF1 levels to the untreated control and suppressed TQ-induced cell cycle arrest and apoptosis. p53-null HCT-116 cells were less sensitive to TQ-induced growth arrest and apoptosis. These results indicate that TQ is antineoplastic and pro-apoptotic against colon cancer cell line HCT116. The apoptotic effects of TQ are modulated by Bcl-2 protein and are linked to and dependent on p53. Our data support the potential for using the agent TQ for the treatment of colon cancer.

Thymoquinone extracted from black seed triggers apoptotic cell death in human colorectal cancer cells via a p53-dependent mechanism.

Mitophagy (mitochondrial autophagy), which removes damaged, effete and superfluous mitochondria, has several distinct variants. In Type 1 mitophagy occurring during nutrient deprivation, preautophagic structures (PAS) grow into cup-shaped phagophores that surround and sequester individual mitochondria into mitophagosomes, a process requiring phosphatidylinositol-3-kinase (PI3K) and often occurring in coordination with mitochondrial fission. After sequestration, the outer compartment of the mitophagosome acidifies, followed by mitochondrial depolarization and ultimately hydrolytic digestion in lysosomes. Mitochondrial damage stimulates Type 2 mitophagy. After photodamage to single mitochondria, depolarization occurs followed by decoration and then coalescence of autophagic LC3-containing structures on mitochondrial surfaces. Vesicular acidification then occurs. By contrast to Type 1 mitophagy, PI3K inhibition does not block Type 2 mitophagy. Further, Type 2 mitophagy is not associated with phagophore formation or mitochondrial fission. A third form of self-eating of mitochondria is formation of mitochondria-derived vesicles (MDVs) enriched in oxidized mitochondrial proteins that bud off and transit into multivesicular bodies. Topologically, the internalization of MDV by invagination of the surface of multivesicular bodies followed by vesicle scission into the lumen is a form of microautophagy, or micromitophagy (Type 3 mitophagy). Cell biological distinctions are the basis for these three types of mitophagy. Future studies are needed to better characterize the molecular and biochemical differences between Types 1, 2 and 3 mitophagy.

Variants of mitochondrial autophagy: Types 1 and 2 mitophagy and micromitophagy (Type 3)

PI3K/Akt signaling in osteosarcoma.

The use of hypoxia models in cell culture has allowed the characterization of the hypoxia response at the cellular, biochemical and molecular levels. Although a decrease in oxygen concentration is the optimal hypoxia model, the problem faced by many researchers is access to a hypoxia chamber or a CO2 incubator with regulated oxygen levels, which is not possible in many laboratories. Several alternative models have been used to mimic hypoxia. One of the most commonly used models is cobalt chloride-induced chemical hypoxia because it stabilizes hypoxia inducible factors 1α and 2α under normoxic conditions. This model has several advantages, and currently, there is a substantial amount of scattered information about how this model works. This review describes the characteristics of the model, as well as the biochemical and molecular bases that support it. The regulation of hypoxia inducible factors by oxygen and the role of CoCl2 are explained to understand the most accepted bases of the CoCl2 -induced hypoxia model. The different current hypotheses that explain the establishment of hypoxic conditions using CoCl2 are also described. Finally, based on the different observations reported in the literature, we provide a critical review about the scope and limitations of this widely used chemical hypoxia model to be informative to all researchers interested in the field.

The use of cobalt chloride as a chemical hypoxia model.

Parkinson’s disease is the second most common neurodegenerative movement disorder; however, its etiology remains elusive. Nevertheless, in vivo observations have concluded that oxidative stress is one of the most common causes in the pathogenesis of Parkinson’s disease. It is known that mitochondria play a crucial role in reactive oxygen species-mediated pathways, and several gene products that associate with mitochondrial function are the subject of Parkinson’s disease research. The PTEN-induced kinase 1 (PINK1) protects cells from mitochondrial dysfunction and is linked to the autosomal recessive familial form of the disease. PINK1 is a key player in many signaling pathways engaged in mitophagy, apoptosis, or microglial inflammatory response and is induced by oxidative stress. Several proteins participate in mitochondrial networks, and they are associated with PINK1. The E3 ubiquitin ligase Parkin, the protease presenilin-associated rhomboid-like serine protease, the tyrosine kinase c-Abl, the protein kinase MARK2, the protease HtrA2, and the tumor necrosis factor receptor-associated protein 1 (TRAP1) provide different steps of control in protection against oxidative stress. Furthermore, environmental toxins, such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, have been identified as contributors to parkinsonism by increasing oxidative stress in dopaminergic neurons. The present review discusses the mechanisms and effects of oxidative stress, the emerging concept of the impact of environmental toxins, and a possible neuroprotective role of the antioxidant astaxanthin in various neurodegenerative disorders with particular emphasis in Parkinson’s disease.

Oxidative Stress-Induced Signaling Pathways Implicated in the Pathogenesis of Parkinson’s Disease

Several pharmacological agents acting on monoamine neurotransmission are used for the management of mental illnesses. Regulation of PI3K/AKT and GSK3 pathways may constitute an important signaling center in the subcellular integration of the synaptic neurotransmission. The pathways also modulate neuronal cell proliferation, migration, and plasticity. There are evidences to suggest that inflammation of neuron contributes to the pathology of depression. Inflammatory activation of neuron contributes to the loss of glial elements, which are consistent with pathological findings characterizing the depression. A mechanism of anti-inflammatory reactions from antidepressant medications has been found to be associated with an enhancement of heme oxygenase-1 expression. This induction in brain is also important in neuroprotection and neuroplasticity. As enzymes involved in cell survival and neuroplasticity are relevant to neurotrophic factor dysregulation, the PI3K/AKT/GSK3 may provide an important signaling for the neuroprotection in depression. In this paper, we summarize advances on the involvement of the PI3K/AKT/GSK3 pathways in cell signaling of neuronal cells in mental illnesses.

/pdf/roles-of-pi3k-akt-gsk3-mtor-pathway-in-cell-signaling-of-2zi8l5atc2.pdf

Roles of pi3k/akt/gsk3/mtor pathway in cell signaling of mental illnesses

Nonalcoholic fatty liver disease (NAFLD) is the most common form of liver pathologies and is associated with obesity and the metabolic syndrome, which represents a range of fatty liver diseases associated with an increased risk of type 2 diabetes. Molecular mechanisms underlying how to make transition from simple fatty liver to nonalcoholic steatohepatitis (NASH) are not well understood. However, accumulating evidence indicates that deregulation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway in hepatocytes is a common molecular event associated with metabolic dysfunctions including obesity, metabolic syndrome, and the NAFLD. A tumor suppressor PTEN negatively regulates the PI3K/AKT pathways through its lipid phosphatase activity. Molecular studies in the NAFLD support a key role for PTEN in hepatic insulin sensitivity and the development of steatosis, steatohepatitis, and fibrosis. We review recent studies on the features of the PTEN and the PI3K/AKT pathway and discuss the protein functions in the signaling pathways involved in the NAFLD. The molecular mechanisms contributing to the diseases are the subject of considerable investigation, as a better understanding of the pathogenesis will lead to novel therapies for a condition.

/pdf/roles-for-pi3k-akt-pten-pathway-in-cell-signaling-of-4m9ooop3x6.pdf

Roles for PI3K/AKT/PTEN Pathway in Cell Signaling of Nonalcoholic Fatty Liver Disease

Mutations in phosphatase and tensin homologue-induced kinase 1 (PINK1) cause recessively inherited Parkinson's disease, a neurodegenerative disorder linked to mitochondrial dysfunction. Studies support the notion of neuroprotective roles for the PINK1, as it protects cells from damage-mediated mitochondrial dysfunction, oxidative stress, and cell apoptosis. PARL is a mitochondrial resident rhomboid serine protease, and it has been reported to mediate the cleavage of the PINK1. Interestingly, impaired mitophagy, an important autophagic quality control mechanism that clears the cells of damaged mitochondria, may also be an underlying mechanism of disease pathogenesis in patients for Parkinson's disease with the PARL mutations. Functional studies have revealed that PINK1 recruits Parkin to mitochondria to initiate the mitophagy. PINK1 is posttranslationally processed, whose level is definitely regulated in healthy steady state of mitochondria. As a consequence, PINK1 plays a pivotal role in mitochondrial healthy homeostasis.

/pdf/function-and-characteristics-of-pink1-in-mitochondria-4h5b9gp3sr.pdf

Function and Characteristics of PINK1 in Mitochondria

Peroxisome proliferator-activated receptors (PPAR) are members of the superfamily of nuclear hormone receptors involved in embryonic development and differentiation of several tissues including placenta, which respond to specific ligands such as polyunsaturated fatty acids by altering gene expression. Three subtypes of this receptor have been discovered, each evolving to achieve different biological functions. The PPARs also control a variety of target genes involved in lipid homeostasis. Similar to other nuclear receptors, the transcriptional activity of PPARs is affected not only by ligand-stimulation but also by crosstalk with other molecules. For example, both PPARs and the RXRs are ligand-activated transcription factors that coordinately regulate gene expression. In addition, several mechanisms underlying negative regulation of gene expression by PPARs have been shown. It is suggested that PPARs are key messengers responsible for the translation of nutritional stimuli into changes in gene expression pathways for placental development.

https://downloads.hindawi.com/journals/ppar/2013/256508.pdf

Expression and Function of PPARs in Placenta

Genetic defects in DNA repair and DNA damage response genes often lead to an increase in cancer incidence. The role of defects is also associated with the modulation of hormone signaling pathways. A number of studies have suggested a role for estrogen in the regulation of DNA repair activity. Furthermore, mutations or epigenetic silencing in DNA repair genes have been associated with the sensitivity of cancers to hormonal therapy. The molecular basis for the progression of cancers from hormone-dependent to hormone-independent remains a critical issue in the management of these types of cancer. In the present review, we aimed to summarize the function of DNA repair molecules from the viewpoint of carcinogenesis and hormone-related cell modulation, providing a comprehensive view of the molecular mechanisms by which hormones may exert their effects on the regulation of tumor progression.

/pdf/defective-dna-repair-systems-and-the-development-of-breast-44gdwrlkdo.pdf

Mayumi Kobayashi

Papers

Roles of pi3k/akt/gsk3/mtor pathway in cell signaling of mental illnesses

Roles for PI3K/AKT/PTEN Pathway in Cell Signaling of Nonalcoholic Fatty Liver Disease

Function and Characteristics of PINK1 in Mitochondria

Expression and Function of PPARs in Placenta

Defective DNA repair systems and the development of breast and prostate cancer (review).