A High-fat Diet Induces a Loss of Midbrain Dopaminergic Neuronal Function That Underlies Motor Abnormalities

Movement defects in obesity are associated with peripheral muscle defects, arthritis, and dysfunction of motor control by the brain. Although movement functionality is negatively correlated with obesity, the brain regions and downstream signaling pathways associated with movement defects in obesity are unclear. A dopaminergic neuronal pathway from the substantia nigra (SN) to the striatum is responsible for regulating grip strength and motor initiation through tyrosine hydroxylase (TH) activity-dependent dopamine release. We found that mice fed a high-fat diet exhibited decreased movement in open-field tests and an increase in missteps in a vertical grid test compared with normally fed mice. This motor abnormality was associated with a significant reduction of TH in the SN and striatum. We further found that phosphorylation of c-Jun N-terminal kinase (JNK), which modulates TH expression in the SN and striatum, was decreased under excess-energy conditions. Our findings suggest that high calorie intake impairs motor function through JNK-dependent dysregulation of TH in the SN and striatum.

Clinical Applications of Antioxidants / 한양의대학술지

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are natural by-products of cellular physiological processes involving metabolism of compounds containing oxygen and nitrogen, respectively. Physiological defense mechanisms against ROS/RNS readily convert them into water or urea, but dysregulation of ROS/RNS production damages cells resulting in abnormal conditions such as uncontrolled growth or cell death. ROS/RNS are closely related to the development of a variety of diseases such as cancer, diabetes, neurodegeneration, vascular disease and chronic inflammation. Thus, it has been proposed that the removal of ROS/RNS may prevent or treat oxidative stress-induced diseases. Some antioxidant molecules are synthesized in the body, while others are obtained from food in the diet including fruits, vegetables, meat and even in natural water. In addition to the natural antioxidants, synthetic antioxidants have been modified from natural chemicals so as to increase bioavailability to target organs and increase stability in the air. In developing novel antioxidants for therapeutic use, some factors to consider are: 1) improved efficacy; 2) low side effects (comparatively clear mechanism); 3) competitive price and 4) improved convenience of dosing. In this review, we will discuss the issues mentioned above and the use of antioxidants in clinical application.

Dexamethasone Induces FcgammaRIIb Expression in RBL-2H3 Cells

Mast cells are involved in allergic responses, protection against pathogens and autoimmune diseases. Dexamethasone (Dex) and other glucocorticoids suppress FcepsilonRI-mediated release of inflammatory mediators from mast cells. The inhibition mechanisms were mainly investigated on the downstream signaling of Fc receptor activations. Here, we addressed the effects of Dex on Fc receptor expressions in rat mast cell line RBL-2H3. We measured mRNA levels of Fc receptors by real-time PCR. As expected, Dex decreased the mRNA levels of activating Fc receptor for IgE (FcepsilonR) I and increased the mRNA levels of the inhibitory Fc receptor for IgG FcgammaRIIb. Interestingly, Dex stimulated transcriptions of other activating receptors such as Fc receptors for IgG (FcgammaR) I and FcgammaRIII. To investigate the mechanisms underlying transcriptional regulation, we employed a transcription inhibitor actinomycin D and a translation inhibitor cycloheximide. The inhibition of protein synthesis without Dex treatment enhanced FcgammaRI and FcgammaRIII mRNA levels potently, while FcepsilonRI and FcgammaRIIb were minimally affected. Next, we examined expressions of the Fc receptors on cell surfaces by the flow cytometric method. Only FcgammaRIIb protein expression was significantly enhanced by Dex treatment, while FcgammaRI, FcgammaRIII and FcepsilonRI expression levels were marginally changed. Our data showed, for the first time, that Dex regulates Fc receptor expressions resulting in augmentation of the inhibitory receptor FcgammaRIIb.

Prevention of TNF-induced necrotic cell death by rottlerin through a Nox1 NADPH oxidase

Previous studies have demonstrated that rottlerin, a specific PKCdelta inhibitor, potentiates death receptor- mediated apoptosis through a cytochrome c-dependent or -independent pathway. However, its ability to regulate necrotic cell death, as well as the underlying mechanism, remains unknown. We found that in murine fibrosarcoma L929 cells, treatment with rottlerin protected the cells against TNF-induced necrosis, whereas it sensitized the cells to apoptosis induced by co-treatment with Hsp90 inhibitor geldanamycin and TNF, in a manner independent of its ability to inhibit PKC-delta. TNF treatment induced rapid accumulation of mitochondrial superoxide (O2") through the Nox1 NADPH oxidase when cells undergo necrosis. Moreover, pretreatment with rottlerin failed to induce the GTP-bound form of small GTPase Rac1 by TNF treatment, and subsequently suppressed mitochondrial O2(-) production and poly(ADP-ribose) polymerase activation, thus inhibiting necrotic cell death. Therefore, our study suggests that Nox1 NADPH oxidase is a new molecular target for anti-necrotic activity of rottlerin upon death-receptor ligation.

Chronic Sublethal Hypoxia Mediates Changes of Astrocytes and RBE4 Cells in Three-dimensional Coculture Models / 대한해부학회지

Chronic sublethal hypoxia induces brain adaptations associated with changes in neurovascular behavior. Changes to the neurovasculature also influence the formation of the brain-blood barrier (BBB). In this study, I investigated the influence of chronic sublethal hypoxia on astrocytes, using the coculture transwell model of primary cultured astrocytes and RBE4 (brain endothelial) cells. Using a 3D collagen gel model, cytoplasmic processes of astrocytes extended to clumps of endothelial cells. The numbers of astrocytes increased in cocultured and chronic hypoxic environments in the transwell model. Western blotting showed increased production of glial fibrillar acidic protein (GFAP) and proliferating cellular nuclear antigen (PCNA) in chronic hypoxia. I also confirmed the influence of hypoxia on the behavior of astrocytes in this model, using confocal microscopy. The numbers of cytoplasmic processes of astrocytes within the membrane increased in z sections. These data support the idea that chronic hypoxia might induce alterations in the formation of the BBB as part of the adaptation of the brain to chronic hypoxia. These transwell and 3D collagen gel models will probably be useful for functional as well as morphological experiments.

Curcumin inhibits the expression of COX-2 in UVB-irradiated human keratinocytes (HaCaT) by inhibiting activation of AP-1: p38 MAP kinase and JNK as potential upstream targets

Ultraviolet B (UVB) irradiation of skin induces an acute inflammation. Cyclooxygenase-2 (COX-2) protein plays key roles in acute inflammation in UVB-irradiated keratinocyte cell line HaCaT. Recently, curcumin has been regarded as a promising anti-inflammatory agent due to its ability to inhibit COX-2 expression. However, it remains largely unknown whether curcumin inhibits the UVB-induced COX-2 expression in HaCaT cells. This study was undertaken to clarify the effect of curcumin on the expression of COX-2 in UVB- irradiated HaCaT cells and further determined the molecular mechanisms associated with this process. In this study, we have found that the expression of COX-2 mRNA and protein were up-regulated in UVB-irradiated HaCaT cells in a dose- and time-dependent manner. Interestingly, treatment with curcumin strongly inhibited COX-2 mRNA and protein expressions in UVB-irradiated HaCaT cells. Notably, there was effective inhibition by curcumin on UVB-induced activations of p38 MAPK and JNK in HaCaT cells. The DNA binding activity of AP-1 transcription factor was also markedly decreased with curcumin treatment in UVB-irradiated HaCaT cells. These results collectively suggest that curcumin may inhibit COX- 2 expression by suppressing p38 MAPK and JNK activities in UVB-irradiated HaCaT cells. We propose that curcumin may be applied as an effective and novel sunscreen drug for the protection of photoinflammation.