Anti-adipogenic effect of epiberberine is mediated by regulation of the Raf/MEK1/2/ERK1/2 and AMPKα/Akt pathways.

It has been reported that alkaloids derived from Coptis chinensis exert anti-adipogenic activity on 3T3-L1 adipocytes by downregulating peroxisome proliferation-activity receptor-γ (PPAR-γ) and CCAAT/enhancer binding protein-α (C/EBP-α). However, the signaling-based mechanism of the inhibitory role of epiberberine in the early stages of 3T3-L1 adipocyte differentiation is uncharacterized. Here, we show that epiberberine had inhibitory effects on adipocyte differentiation and significantly decreased lipid accumulation by downregulating an adipocyte-specific transcription factor, sterol regulatory element-binding protein-1 (SREBP-1). Furthermore, we observed that epiberberine markedly suppressed the differentiation-mediated phosphorylation of components of both the Raf/mitogen-activated protein kinase 1 (MEK1)/extracellular signal-regulated protein kinase 1/2 (ERK1/2) and AMP-activated protein kinase-α1 (AMPKα)/Akt pathways. In addition, gene expression of fatty acid synthase (FAS) was significantly inhibited by treatment with epiberberine during adipogenesis. These results indicate that the anti-adipogenic mechanism of epiberberine is associated with inhibition of phosphorylation of Raf/MEK1/ERK1/2 and AMPKα/Akt, followed by downregulation of the major transcription factors of adipogenesis, such as PPAR-γ, C/EBP-α, and SREBP-1, and FAS. Taken together, this study suggests that the anti-adipogenic effect of epiberberine is mediated by downregulation of the Raf/MEK1/ERK1/2 and AMPKα/Akt pathways during 3T3-L1 adipocyte differentiation. Moreover, the anti-adipogenic effects of epiberberine were not accompanied by modulation of ß-catenin.

N-acetylcysteine attenuates hexavalent chromium-induced hypersensitivity through inhibition of cell death, ROS-related signaling and cytokine expression.

Chromium hypersensitivity (chromium-induced allergic contact dermatitis) is an important issue in occupational skin disease. Hexavalent chromium (Cr (VI)) can activate the Akt, Nuclear factor κB (NF-κB), and Mitogen-activated protein kinase (MAPK) pathways and induce cell death, via the effects of reactive oxygen species (ROS). Recently, cell death stimuli have been proposed to regulate the release of inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1). However, the exact effects of ROS on the signaling molecules and cytotoxicity involved in Cr(VI)-induced hypersensitivity have not yet been fully demonstrated. N-acetylcysteine (NAC) could increase glutathione levels in the skin and act as an antioxidant. In this study, we investigated the effects of NAC on attenuating the Cr(VI)-triggered ROS signaling in both normal keratinocyte cells (HaCaT cells) and a guinea pig (GP) model. The results showed the induction of apoptosis, autophagy and ROS were observed after different concentrations of Cr(VI) treatment. HaCaT cells pretreated with NAC exhibited a decrease in apoptosis and autophagy, which could affect cell viability. In addition, Cr (VI) activated the Akt, NF-κB and MAPK pathways thereby increasing IL-1α and TNF-α production. However, all of these stimulation phenomena could be inhibited by NAC in both of in vitro and in vivo studies. These novel findings indicate that NAC may prevent the development of chromium hypersensitivity by inhibiting of ROS-induced cell death and cytokine expression.

The marine fungal metabolite, AD0157, inhibits angiogenesis by targeting the Akt signaling pathway.

In the course of a screening program for the inhibitors of angiogenesis from marine sources, AD0157, a pyrrolidinedione fungal metabolite, was selected for its angiosupressive properties. AD0157 inhibited the growth of endothelial and tumor cells in culture in the micromolar range. Our results show that subtoxic doses of this compound inhibit certain functions of endothelial cells, namely, differentiation, migration and proteolytic capability. Inhibition of the mentioned essential steps of in vitro angiogenesis is in agreement with the observed antiangiogenic activity, substantiated by using two in vivo angiogenesis models, the chorioallantoic membrane and the zebrafish embryo neovascularization assays, and by the ex vivo mouse aortic ring assay. Our data indicate that AD0157 induces apoptosis in endothelial cells through chromatin condensation, DNA fragmentation, increases in the subG1 peak and caspase activation. The data shown here altogether indicate for the first time that AD0157 displays antiangiogenic effects, both in vitro and in vivo, that are exerted partly by targeting the Akt signaling pathway in activated endothelial cells. The fact that these effects are carried out at lower concentrations than those required for other inhibitors of angiogenesis makes AD0157 a new promising drug candidate for further evaluation in the treatment of cancer and other angiogenesis-related pathologies.

20(S)-protopanaxadiol triggers mitochondrial-mediated apoptosis in human lung adenocarcinoma A549 cells via inhibiting the PI3K/Akt signaling pathway.

20(S)-Protopanaxadiol (PPD), an aglycone saponin ginsenoside isolated from Panax quinquefolium L, has been shown to inhibit the growth and proliferation in several cancer lines. However, the underlying molecular mechanisms remain poorly understood. In this study, we investigated the apoptosis-induced effects and the mechanism of 20(S)-PPD on human lung adenocarcinoma A549 cells. 20(S)-PPD showed a potent antiproliferative activity against A549 cells by triggering apoptosis. 20(S)-PPD-induced apoptosis was characterized by a dose-dependent loss of the mitochondrial membrane, release of cytochrome c, second mitochondria-derived activator of caspase (Smac) and apoptosis-inducing factor (AIF), activation of caspase-9/-3, and cleavage of poly (ADP-ribose) polymerase (PARP). Caspase-dependence was indicated by the ability of the pan-caspase inhibitor z-VAD-fmk to attenuate 20(S)-PPD-induced apoptosis. After treatment with 20(S)-PPD, the proportion of A549 cells at the G0/G1 phase increased, while cells at the S and G2/M phases decreased. Furthermore, 20(S)-PPD also triggered down-regulation of phosphorylated Akt (Ser473/Thr308) and glycogen synthase kinase 3ß (GSK 3ß). Knockdown of GSK 3ß with siRNA promoted the apoptotic effects of 20(S)-PPD. These results revealed an unexpected mechanism of action for this unique ginsenoside: triggering a mitochondrial-mediated, caspase-dependent apoptosis via down-regulation of the PI3K/Akt signaling pathway in A549 cells. Our findings encourage further studies of 20(S)-PPD as a promising chemopreventive agent against lung cancer.

LEOPARD-type SHP2 mutant Gln510Glu attenuates cardiomyocyte differentiation and promotes cardiac hypertrophy via dysregulation of Akt/GSK-3ß/ß-catenin signaling.

LEOPARD syndrome (LS) is an autosomal dominant inherited multisystemic disorder. Most cases involve mutations in the PTPN11 gene, which encodes the protein tyrosine phosphatase Src homology 2-containing protein phosphatase 2 (SHP2). LS frequently causes severe hypertrophic cardiomyopathy (HCM), even from the fetal period. However, the molecular pathogenesis has not been clearly elucidated. Here, we analyzed the roles of the LS-type SHP2 mutant Gln510Glu (Q510E), which showed the most severe type of HCM in LS, in cardiomyocyte differentiation, and in morphological changes. We generated mutant P19CL6 cell lines, the most convenient cardiomyocyte differentiation model, which continuously expressed SHP2-Q510E, SHP2-D61N (Noonan-type mutant), wild-type SHP2, and green fluorescent protein (native SHP2 expression only). SHP2-Q510E mutant P19CL6 cells showed significant attenuation of myofibrillogenesis, with increased proliferative activity. Mature cardiomyocytes from the SHP2-Q510E mutant were significantly larger than those of controls and the other mutants. However, expression of cardiac-specific transcriptional factors (Gata4, Tbx5, and Nkx2.5) did not differ significantly between the LS-type SHP2-Q510E mutants and the other mutants and controls. Our results indicate that SHP2-Q510E mutants can differentiate into cardiac progenitors but are inhibited from undergoing terminal differentiation into mature cardiomyocytes. In contrast, Akt and glycogen synthase kinase (GSK)-3ß phosphorylation were upregulated, and nuclear ß-catenin at the late stage of differentiation was highly accumulated in SHP2-Q510E mutant P19CL6 cells. Supplementation with the phosphoinositide 3-kinase/Akt inhibitor LY-294002 during the late stage of differentiation was found to partially restore myofibrillogenesis while suppressing the increase in size of individual mature cardiomyocytes derived from the SHP2-Q510E mutants. Our findings suggest that dysregulation of the Akt/GSK-3ß/ß-catenin pathway can contribute to the pathogenesis of HCM in LS patients, not only through hypertrophic changes in individual cardiac cells but also via the expansion of cardiac progenitors.

The molecular mechanism of leptin secretion and expression induced by aristolochic acid in kidney fibroblast.

BACKGROUND: Leptin is a peptide hormone playing pivotal role in regulating food intake and energy expenditure. Growing evidence has suggested the pro-inflammatory and fibrogenic properties of leptin. In addition, patients with renal fibrosis have higher level of plasma leptin, which was due to the increased leptin production. Aristolochic acid (AA) is a botanical toxin characterized to associate with the development of renal fibrosis including tubulointerstitial fibrosis. However, whether leptin is upregulated to participate in AA-induced kidney fibrosis remain completely unknown. METHODOLOGY/PRINCIPAL FINDINGS: In this study, leptin expression was increased by sublethal dose of AA in kidney fibroblast NRK49f determined by enzyme-linked immunosorbent assay and Western blot. Data from real-time reverse transcriptase-polymerase chain reaction revealed that leptin was upregulated by AA at transcriptional level. DNA binding activity of CCAAT enhancer binding protein α (C/EBP α), one of the transcription factors for leptin gene, was enhanced in DNA affinity precipitation assay and chromatin immunoprecipitation experiments. Knockdown of C/EBP α expression by small interfering RNA markedly reduced AA-induced leptin expression. Moreover, AA promoted Akt interaction with p-PDK1, and increased phosphorylated activation of Akt. Akt knockdown, and inhibition of Akt signaling by LY294002 and mTOR inhibitor rapamycin reduced leptin expression. Furthermore, treatment of LY294002 or rapamycin significantly suppressed AA-induced C/EBP α DNA-binding activity. These results suggest that Akt and C/EBP α activation were involved in AA-regulated leptin expression. CONCLUSIONS/SIGNIFICANCE: Our findings demonstrate the first that AA could induce secretion and expression of fibrogenic leptin in kidney fibroblasts, which reveal potential involvement of leptin in the progression of kidney fibrosis in aristolochic acid nephropathy.

Inhibition of activated phosphatidylinositol 3-kinase/AKT pathway in malignant pleural mesothelioma leads to G1 cell cycle arrest.

Phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway plays pivotal roles in fundamental cellular functions including cell proliferation and cell survival. Its deregulation has been implicated in many types of human malignancies. We investigated the role of PI3K/AKT signaling pathway in human malignant pleural mesothelioma (MM). Here, we report that aberrant activation of the PI3K/AKT signaling pathway is associated with cell cycle progression in MM cells. Inhibition of the PI3K activity by its small molecule inhibitor LY294002 led to significant G1 cell cycle arrest and suppression of cell proliferation in all MM cell lines that we examined. In addition, we found that the protein level of p27Kip1 was up-regulated and the protein level of cyclin D1 was down-regulated following LY294002 treatment in those MM cell lines. However, no noticeable apoptosis induction was observed following 24 h of LY294002 treatment in those MM cell lines. These results confirm that the PI3K/AKT signaling pathway is aberrantly active and plays a critical role for the cell cycle progression in human MM cells.

Tamoxifen-induced apoptosis of rat C6 glioma cells via PI3K/Akt, JNK and ERK activation.

To elucidate the mechanism of TAM treatment on gliomas, we hypothesised that PI3K/Akt and MAPK signaling pathway may play important roles on TAM-induced apoptosis in C6 glioma cells. Our results demonstrated that TAM induced apoptosis of C6 glioma cells in a dose-dependent manner. The activation of AKT significantly decreased in a time-dependent manner in response to TAM treatment, JNK was transiently activated, and subsequently decreased activation and kept stable level, whereas ERK evidenced sustained activations in response to the drug treatment. The inhibition of PI3K/Akt and JNK both accelerated and enhanced TAM-induced apoptosis and ERK inhibition apparently exerted negative effect on apoptosis. We also observed that PI3K/Akt had intimate association with JNK and ERK activation in TAM-induced apoptosis. These findings may provide strategies for the molecularly targeted therapy in malignant gliomas.

Poststress treatment with PNU282987 can rescue SH-SY5Y cells undergoing apoptosis via α7 nicotinic receptors linked to a Jak2/Akt/HO-1 signaling pathway.

Most neuroprotection studies with nicotinic agonists have shown efficacy when given before the stressor. Here we have investigated whether the α7 nicotinic acetylcholine receptor (nAChR) agonist PNU282987 can prevent cell death once the cells have already undergone an oxidative stress. The combination of rotenone (30 µM) plus oligomycin A (10 µM) (rot/oligo) has been used as an in vitro model of mitochondrial ROS production. SH-SY5Y cells incubated with rot/oligo for 8h and left for another 16 h in MEM/F-12 experienced 30% apoptotic cell death. Under these experimental conditions, PNU282987 administered after rot/oligo (PST/PNU) prevented cell death in a concentration-dependent manner. Co-incubation of PNU282987 with 100 nM methyllycaconitine (a selective α7 nAChR antagonist), 10 µM mecamylamine (a nonselective nAChR antagonist), 3 µM LY294002 (a PI3K inhibitor), or 10 µM AG490 (a Jak2 inhibitor) prevented the protection afforded by PST/PNU. Moreover, the increase in ROS, active caspase-3, and apoptosis caused by rot/oligo was also prevented by PST/PNU. Furthermore, PNU282987 increased the expression of heme oxygenase-1 (HO-1), a critical cell defense enzyme against oxidative stress; this increase was prevented by AG490 or LY294002. The HO-1 inhibitor Sn(IV) protoporphyrin-IX also inhibited the PST/PNU protecting effects. These results suggest that activation of α7 nAChR linked to the Jak2/PI3K/Akt cascade induces the antioxidant enzyme HO-1 to provide neuroprotection.

Akt associates with nuclear factor kappaB and plays an important role in chemoresistance of gastric cancer cells.

The ubiquitously expressed serine-threonine kinase Akt and the transcription factor NF-kappaB both are involved in cell proliferation and apoptosis. Furthermore, the activation of Akt or NF-kappaB has been suggested to associate with chemo-resistance of human tumors. The exact mechanism and interreaction of Akt and NF-kappaB pathway on chemoresistance in gastric cancer is still unknown. We explored the function of Akt and NF-kappaB pathway on chemoresistance in human gastric cancer cells. MTT method was used to analyze the influence of chemotherapeutics and the combined use of wortmannin or MG-132 on the growth of SGC-7901 cells. Apoptosis of SGC-7901 was detected by TUNEL and Annexin V/PI methods. The protein level of NF-kappaB was analyzed by immunocytochemical staining. EMSA was used to confirm the increased nuclear translocation of RelA. The protein level of p-Akt and p-IkappaBalpha were analyzed by Western blotting. Etoposide and doxorubicin suppressed the growth of SGC-7901 time and dose-dependently. Combined use of wortmannin or MG-132 can suppress growth further. Chemotherapeutics induced apoptosis of SGC-7901 and activated Akt and NF-kappaB, combined use of wortmannin or MG-132 induced apoptosis further and attenuated the activation of NF-kappaB. The combined use of wortmannin attenuated the activation of Akt, but combined use of MG-132 did not attenuate the activation of Akt. The activation of NF-kappaB is a branch mechanism of Akt anti-apoptosis effects. The chemotherapeutics induced apoptosis and induced the activation of Akt and NF-kappaB in SGC-7901 cell, suppression the activation of Akt or NF-kappaB can increase the effects of chemotherapeutics. NF-kappaB is a downstream target of Akt.

Green tea polyphenol epigallocatechin gallate reduces endothelin-1 expression and secretion in vascular endothelial cells: roles for AMP-activated protein kinase, Akt, and FOXO1.

Epigallocatechin gallate (EGCG), a green tea polyphenol, promotes vasodilation by phosphatidylinositol 3-kinase-dependent activation of Akt and endothelial nitric oxide synthase to stimulate production of nitric oxide. Reduction in endothelin-1 (ET-1) synthesis may also increase bioavailability of nitric oxide. We hypothesized that the phosphatidylinositol 3-kinase-dependent transcription factor FOXO1 may mediate effects of EGCG to regulate expression of ET-1 in endothelial cells. EGCG treatment (10 microm, 8 h) of human aortic endothelial cells reduced expression of ET-1 mRNA, protein, and ET-1 secretion. We identified a putative FOXO binding domain in the human ET-1 promoter 51 bp upstream from the transcription start site. Trans-activation of a human ET-1 (hET-1) promoter luciferase reporter was enhanced by coexpression of a constitutively nuclear FOXO1 mutant, whereas expression of a mutant FOXO1 with disrupted DNA binding domain did not trans-activate the hET-1 promoter. Disrupting the hET-1 putative FOXO binding domain by site-directed mutagenesis ablated promoter activity in response to overexpression of wild-type FOXO1. EGCG stimulated time-dependent phosphorylation of Akt (S(473)), FOXO1 (at Akt phosphorylation site T(24)), and AMP-activated protein kinase alpha (AMPK alpha) (T(172)). EGCG-induced nuclear exclusion of FOXO1, FOXO1 binding to the hET-1 promoter, and reduction of ET-1 expression was partially inhibited by the AMPK inhibitor Compound C. Basal ET-1 protein expression was enhanced by short interfering RNA knock-down of Akt and reduced by short interfering RNA knock-down of FOXO1 or adenovirus-mediated expression of dominant-negative Foxo1. We conclude that EGCG decreases ET-1 expression and secretion from endothelial cells, in part, via Akt- and AMPK-stimulated FOXO1 regulation of the ET-1 promoter. These findings may be relevant to beneficial cardiovascular actions of green tea.

Evodiamine-induced human melanoma A375-S2 cell death was mediated by PI3K/Akt/caspase and Fas-L/NF-kappaB signaling pathways and augmented by ubiquitin-proteasome inhibition.

Evodiamine, a major alkaloidal component of Evodiae fructus exhibits anti-tumor activities. We have previously reported that evodiamine has a marked inhibitory effect on IL-1 sensitive human melanoma A375-S2 cells proliferation, and this action might be through inactivation of PI3K signaling. However, the detailed molecular mechanisms of evodiamine-induced cell death remains poorly understood. In present study, we further confirmed that Akt is the main effector molecule involved in this pathway. Evodiamine also led to IkappaBalpha phosphorylation and degradation that reflect translocation of NF-kappaB. Pretreatment of A375-S2 cells with ubiquitin-proteasome inhibitor MG132 was shown to aggregate the evodiamine caused cell death at 24h. In addition, MG132 reduced ERK phosphorylation, increased caspase-3 activation, Fas-L expression and Bcl-2 cleavage in evodiamine-treated A375-S2 cells. These results suggested the PI3K/Akt/caspase and Fas-L/NF-kappaB signaling pathways might account for the responses of A375-S2 cell death induced by evodiamine, and these signals could be augmented by ubiquitin-proteasome pathway.

FOXO transcription factors and VEGF neutralizing antibody enhance antiangiogenic effects of resveratrol.

Resveratrol (trans-3,5,4'-trihydroxystilbene), a compound found largely in the skins of red grapes and wines, possesses anti-cancer and anti-angiogenic properties and protects the cardiovascular system. However, the molecular mechanisms by which resveratrol inhibits angiogenesis are currently subjects of intense investigation. The purpose of this study was to examine whether FOXO transcription factors mediate anti-angiogenic effects of resveratrol, and whether vascular endothelial growth factor (VEGF) neutralizing antibody can enhance these effects of resveratrol. Inhibition of PI3 kinase (PI3K)/AKT and MEK/ERK pathways synergistically inhibited migration and capillary tube formation of Human Umbilical Vein Endothelial Cells (HUVECs) and further enhanced the anti-angiogenic effects of resveratrol. Inhibitors of AKT and MEK kinase synergistically inhibited cytoplasmic FOXO3a phosphorylation, which was accompanied by its nuclear translocation in HUVECs. Interestingly, inhibition of PI3K/AKT and MEK/ERK pathways synergistically induced FOXO transcriptional activity and inhibited cell migration and capillary tube formation. Antiangiogenic effects of resveratrol were enhanced by inhibitors of AKT and MEK. Phosphorylation-deficient mutants of FOXOs induced FOXO transcriptional activity, inhibited HUVEC cell migration, and capillary tube formation, and also enhanced antiangiogenic effects of resveratrol. Finally, VEGF neutralizing antibody enhanced the anti-proliferative and anti-angiogenic effects of resveratrol. In conclusion, regulation of FOXO transcription factors by resveratrol may play an important role in angiogenesis which is critical for cancer, diabetic retinopathy, rheumatoid arthritis, psoriasis, and cardiovascular disorders.

Dexamethasone interferes with trastuzumab-induced cell growth inhibition through restoration of AKT activity in BT-474 breast cancer cells.

The combination of trastuzumab with paclitaxel (PTX) is an important option for the treatment of HER2-positive breast cancer. Dexamethasone (Dex) premedication is routinely used in the treatment with PTX. The interactions among Dex, PTX and trastuzumab were evaluated in BT-474 cells. Dex interfered with trastuzumab-induced cell growth inhibition without clear effects on PTX-induced cytotoxicity. Trastuzumab dephosphorylated retinoblastoma protein (pRB). Dex restored this trastuzumab-induced dephosphorylation of pRB and released trastuzumab-induced G1 arrest. Trastuzumab suppressed AKT activity without affecting ERK activity. A specific inhibitor for the phosphatidylinositol 3-kinase/AKT pathway, LY294002, inhibited cell growth and AKT and pRB phosphorylation. Dex restored the trastuzumab-induced suppression of AKT without affecting ERK activity. It was concluded that Dex interferes with trastuzumab-induced cell growth inhibition, at least partially, through the restoration of trastuzumab-induced AKT suppression and subsequent pRB dephosphorylation in BT-474 breast cancer cells. These observations support the development of new chemotherapeutic regimens without glucocorticoid premedication.

Water extract of Korean red ginseng stimulates angiogenesis by activating the PI3K/Akt-dependent ERK1/2 and eNOS pathways in human umbilical vein endothelial cells.

Angiogenesis is important for promoting cardiovascular disease, wound healing, and tissue regeneration. We investigated the effects of Korean red ginseng water extract (KRGE) on angiogenesis and its underlying signal mechanism. KRGE increased in vitro proliferation, migration, and tube formation of human umbilical vein endothelial cells, as well as stimulated in vivo angiogenesis without increasing VEGF expression. KRGE-induced angiogenesis was accompanied by phosphorylation of ERK1/2, phosphatidylinositol 3-kinase (Akt), and endothelial nitric oxide synthase (eNOS) as well as an increase in NO production. Inhibition of PI3K activity by wortmannin completely inhibited KRGE-induced angiogenesis and phosphorylation of Akt, ERK1/2, and eNOS, indicating that PI3K/Akt activation is an upstream event of the KRGE-mediated angiogenic pathway. The MEK inhibitor PD98059 blocked KRGE-induced ERK1/2 phosphorylation without affecting Akt and eNOS activation. However, the eNOS inhibitor N(G)-monomethyl-L-arginine effectively inhibited tube formation, but partially blocked proliferation and migration as well as ERK phosphorylation, without altering Akt and eNOS activation, revealing that the eNOS/NO pathway is partially involved in ERK1/2 activation. This study demonstrated that KRGE stimulates in vitro and in vivo angiogenesis through the activation of the PI3K/Akt-dependent ERK1/2 and eNOS signal pathways and their cross talk.

Protein kinase B/Akt modulates nephrotoxicant-induced necrosis in renal cells.

Protein kinase B (Akt) activation is well known for its protective effects against apoptosis. However, the role of Akt in regulation of necrosis is unknown. This study was designed to test whether Akt activation protects against nephrotoxicant-induced injury and death in renal proximal tubular cells (RPTC). Exposure of primary cultures of RPTC to the nephrotoxic cysteine conjugate, S-(1,2-dichlorovinyl)-l-cysteine (DCVC), resulted in 9% apoptosis and 30% necrosis at 24 h following the exposure. Akt was activated during 8 h but not at 24 h following toxicant exposure. No RPTC necrosis was observed during Akt activation. Blocking Akt activation using a phosphatidylinositol 3-kinase inhibitor, LY294002 (20 muM), or expressing dominant negative (inactive) Akt increased DCVC-induced RPTC necrosis to 42%. In contrast, Akt activation by expression of constitutively active Akt diminished necrosis to 15%. Modulation of Akt activity had no effect on DCVC-induced apoptosis. DCVC-induced RPTC injury was accompanied by decreases in respiration (51% of controls) and ATP levels (57% of controls). Akt inhibition exacerbated decreases in RPTC respiration and intracellular ATP content (both to 30% of controls). In contrast, Akt activation reduced DCVC-induced decreases in respiration (80% of controls) and prevented decline in ATP content. These data show that in RPTC, Akt activation reduces 1) toxicant-induced mitochondrial dysfunction, 2) decreases in ATP levels, and 3) necrosis. We conclude that Akt activation plays a protective role against necrosis caused by nephrotoxic insult in RPTC. Furthermore, we identified mitochondria as a subcellular target of protective actions of Akt against necrosis.

Mouse modeling in oncologic preclinical and translational research.

Through scientific and technological advancements, our ability to manipulate the mouse genome has allowed us to evaluate the effect of specific genetic alterations on in vivo tumorigenesis. This has allowed and will allow us to define molecular pathways describing the processes of tumor initiation, invasion, and progression to metastatic disease. Additionally, these models may serve as an excellent platform for the identification of novel molecular targets for therapy as well as to evaluate the efficacy of targeted therapies. Ultimately this will translate from preclinical mouse model trials to the development of clinical trials and protocols for cancer patients. Here we review the usefulness of mouse modeling in oncologic translational research.