Protein kinase Cδ mediates trimethyltin-induced neurotoxicity in mice in vivo via inhibition of glutathione defense mechanism

We investigated whether protein kinase C (PKC) is involved in trimethyltin (TMT)-induced neurotoxicity. TMT treatment (2.8 mg/kg, i.p.) significantly increased PKCδ expression out of PKC isozymes (i.e., α, βI, βII, δ, and ?) in the hippocampus of wild-type (WT) mice. Consistently, treatment with TMT resulted in significant increases in cleaved PKCδ expression. Genetic or pharmacological inhibition (PKCδ knockout or rottlerin) was less susceptible to TMT-induced seizures than WT mice. TMT treatment increased glutathione oxidation, lipid peroxidation, protein oxidation, and levels of reactive oxygen species. These effects were more pronounced in the WT mice than in PKCδ knockout mice. In addition, the ability of TMT to induce nuclear translocation of Nrf2, Nrf2 DNA-binding activity, and upregulation of γ-glutamylcysteine ligase was significantly increased in the PKCδ knockout mice and rottlerin (10 or 20 mg/kg, p.o. × 6)-treated WT mice. Furthermore, neuronal degeneration (as shown by nuclear chromatin clumping and TUNEL staining) in WT mice was most pronounced 2 days after TMT. At the same time, TMT-induced inhibition of phosphoinositol 3-kinase (PI3K)/Akt signaling was evident, thereby decreasing phospho-Bad, expression of Bcl-xL and Bcl-2, and the interaction between phospho-Bad and 14-3-3 protein, and increasing Bax expression and caspase-3 cleavage were observed. Rottlerin or PKCδ knockout significantly protected these changes in anti- and pro-apoptotic factors. Importantly, treatment of the PI3K inhibitor LY294002 (0.8 or 1.6 µg, i.c.v.) 4 h before TMT counteracted protective effects (i.e., Nrf-2-dependent glutathione induction and pro-survival phenomenon) of rottlerin. Therefore, our results suggest that down-regulation of PKCδ and up-regulations of Nrf2-dependent glutathione defense mechanism and PI3K/Akt signaling are critical for attenuating TMT neurotoxicity.     

The in vitro pharmacological profile of KR31080, a nonpeptide AT1 receptor antagonist

Summary— KR31080 (2-butyl-5-methyl-6-(1-oxopyridin-2-yl)-3-[[2'-(1H-tetrazol-5-yl) biphenyl-4-yl]methyl]-3H-imidazo[4,5-b] pyridine) is a potent inhibitor of angiotensin type 1 (AT₁) receptors in rabbit aorta and human recombinant AT₁ receptors. In the isolated rabbit thoracic aorta, KR31080 caused a nonparallel shift to the right of the concentration-response curves to angiotensin II (All) with decreased maximal response (pD'₂ = 10.1 ± 0.1), but had no effect on the contractile response induced by norepinephrine. KR31080 inhibited specific [¹²⁵I]AII binding to rabbit aortic membranes (AT, receptors) and [¹²⁵I][Sar¹, Ile⁸]AII binding to human recombinant AT₁ receptors in a concentration-dependent manner with IC₅₀ values of 0.84 ± 0.08 nM and 1.92 ± 0.15 nM, respectively, but did not inhibit specific [¹²⁵I)AII binding to bovine cerebellum membranes (ÀT₂ receptors). In the Scatchard analysis, KR31080 interacted with rabbit aortic AT₁ receptors in a competitive manner, similar to losartan. These results demonstrate that KR31080 is a potent and AT₁ selective angiotensin receptor antagonist which exerts a competitive antagonism in the [¹²⁵I]AII binding assay and insurmountable AT₁ receptor antagonism in the functional study.     

四川龙胆的三萜成分

四川龙胆系龙胆科龙胆属植物 ,生于山野坡林下及水湿地带主要分布于云南、四川、贵州等地 ,一年生草本植物 ,高 2 .5 8m;茎直立 ,黄绿色 ;叶稍带肉质 ,稍尖 ,两面有光泽 ;根部有很多分枝[1,2 ] 。龙胆科植物在《神农本草经》中作为中品收载[3 ] ,具有泻胆肝火 ,清热燥湿的功效。用于骨间寒热 ,湿热黄疸 ,寒湿脚气 ,咽喉痛 ,目赤 ,口苦 ,阴部湿痒等证 [4]。在临床上广泛应用 ,自 1 91 3年 Ashahina等从该属植物的根部分离得到苦味成分龙胆苦碱( gentiopicrin)以来[5] ,对该属植物的化学成分已有大量研究报道 ,主要含生物碱 ,黄酮类 ,酚类 ,…     

Notochordal cells stimulate migration of cartilage end plate chondrocytes of the intervertebral disc in in vitro cell migration assays

Background contextIt was recently demonstrated that the postnatal transition from a notochordal to a fibrocartilaginous nucleus pulposus (NP) is accomplished exogenously by chondrocytes migrating from hyaline cartilage end plates (CEs) into the ectopic notochordal NP region. Although our previous in vivo studies showed evidences for the migration of CE chondrocyte from hyaline CEs into the notochordal NP, it is unknown whether CE chondrocytes of the intervertebral disc (IVD) really have a motile property. In addition, the effect of notochordal cells on this property has not been elucidated.PurposeThe purpose of this in vitro study was to demonstrate whether CE chondrocytes of the IVD are capable of migration, and whether there is any biological link between notochordal cells and CE chondrocytes that may regulate the CE chondrocyte migration.Study design/settingIn vitro cell migration assays were performed using rat IVDs.MethodsNotochordal cells and chondrocytes were obtained from the NP and CE tissues, respectively, and were cultured separately. The different numbers of notochordal cells and the supernatant (conditioned medium) that contained soluble factors produced by notochordal cells were used to demonstrate their effects on the migration of CE chondrocytes. Bovine serum albumin (BSA) and lysophosphatidic acid (LPA) were used as negative and positive controls, respectively.ResultsCompared with BSA, LPA, notochordal cells (N=4×, 2×, 1×, and 0.5×10⁵), and its conditioned media (unconcentrated and fivefold concentrated) significantly increased migration of CE chondrocytes (p<.05 in all comparisons). Particularly, notochordal cells and its conditioned media increased migration in a number- and concentration-dependent manner, respectively.ConclusionsThis study demonstrates that CE chondrocytes of the IVD are capable of migration and that soluble factors produced by notochordal cells stimulate the migration. These results provide a plausible explanation to the question of why CE chondrocytes of the IVD migrate into the ectopic NP region during the natural transition from the notochordal to fibrocartilaginous NP.     

Fractal analysis of the PDL-bone interface and implications for orthodontic tooth movement

BACKGROUND: The periodontal ligament (PDL) is a soft tissue interposed between the tooth and the alveolar bone. It is responsible for transmission of forces in vivo; this promotes bone remodeling. The purpose our study was to use fractal analysis to quantify the complex morphology of the PDL-bone interface. METHODS: We used Scion Image (Scion Corp, Frederick, Md) and Benoit fractal analysis (Tru Soft International, St. Petersburg, Fla) programs to calculate the fractal dimension of the PDL-bone interface in rats via the box-counting method. Rats in the experimental groups received an initial force of 0.1N or 0.5N with customized springs for 6 hours. RESULTS: Our studies showed an increase in normal fractal dimension at the root apices of the rats' maxillary molars. We also found evidence that the fractal dimension varies along the entire root length from the apex to the cementoenamel junction. CONCLUSIONS: Mechanical loading might lead to an increase in fractal dimension at the PDL-bone interface apart from mechanisms of bone cell directed remodeling. These changes in fractal dimension are proportional to loading and could provide a new parameter for force determination in orthodontic tooth movement.