Sustained induction of survival p-AKT and p-ERK signals after transient hypoxia in mice spinal cord with G93A mutant human SOD1 protein

In Vivo Imaging of Oxidative and Hypoxic Stresses in Mice Model of Amyotrophic Lateral Sclerosis

Oxidative and hypoxic stresses are associated with the degeneration of both motor neurons and skeletal muscles in amyotrophic lateral sclerosis (ALS). In vivo bioluminescent imaging is used to monitor cellular responses to oxidative and hypoxic stresses in living ALS model mice bearing G93A-human Cu/Zn superoxide dismutase (SOD1) longitudinally using the IVIS spectrum imaging system. Double transgenic mice bearing both Keap1-dependent oxidative stress detector No-48 (OKD48) and G93A-SOD1 are useful for in vivo imaging of oxidative stress in ALS. We developed a bioluminescence resonance energy transfer (BRET) probe that is regulated by HIF-1α-specific ubiquitin-proteasome system. G93A-SOD1 mice injected with the BRET probe are useful to investigate the spatiotemporal responses to hypoxic stress in ALS. In this chapter, we introduce a practical protocol of in vivo imaging of both oxidative and hypoxic stress in ALS model mice.

Hypoxic stress visualized in the cervical spinal cord of ALS patients

Objective: Amyotrophic lateral sclerosis (ALS) is a progressive and fatal motor neuron disease. Hypoxic stress is suspected as the pathogenesis of ALS, however, no positron emission tomography (PET) study for hypoxic stress has been conducted in the spinal cord of ALS patients.Methods: In the present study, we examined cervical spinal hypoxic stress of nineALS patients with upper extremity (U/E) atrophy by¹⁸F-fluoromisonidazole (FMISO) PET.Results: On the ipsilateral side of C1 and C5 levels, ¹⁸F-FMISO uptake increased significantly compared with the contralateral side (*p < 0.05) and the control subject (**p < 0.01). In addition, a strong correlation was found between ¹⁸F-FMISO uptake of the C5 level and the rate of progression of the ALS FRS-R score (R = 0.781, *p = 0.013).Conclusion: These results indicate that hypoxic stress increased in the spinal cord of ALS patients with a close link to ALS progression. Both hypoxic stress and a compromised response to hypoxia, which may lead to subsequent motor neuron death, could be a potential therapeutic target for ALS.

FM19G11-Loaded Gold Nanoparticles Enhance the Proliferation and Self-Renewal of Ependymal Stem Progenitor Cells Derived from ALS Mice

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease affecting motor neurons. In ALS mice, neurodegeneration is associated with the proliferative restorative attempts of ependymal stem progenitor cells (epSPCs) that normally lie in a quiescent in the spinal cord. Thus, modulation of the proliferation of epSPCs may represent a potential strategy to counteract neurodegeneration. Recent studies demonstrated that FM19G11, a hypoxia-inducible factor modulator, induces epSPC self-renewal and proliferation. The aim of the study was to investigate whether FM19G11-loaded gold nanoparticles (NPs) can affect self-renewal and proliferation processes in epSPCs isolated from G93A-SOD1 mice at disease onset. We discovered elevated levels of SOX2, OCT4, AKT1, and AKT3, key genes associated with pluripotency, self-renewal, and proliferation, in G93A-SOD1 epSPCs at the transcriptional and protein levels after treatment with FM19G11-loaded NPs. We also observed an increase in the levels of the mitochondrial uncoupling protein (UCP) gene in treated cells. FM19G11-loaded NPs treatment also affected the expression of the cell cycle-related microRNA (miR)-19a, along with its target gene PTEN, in G93A-SOD1 epSPCs. Overall our findings establish the significant impact of FM19G11-loaded NPs on the cellular pathways involved in self-renewal and proliferation in G93A-SOD1 epSPCs, thus providing an impetus to the design of novel tailored approaches to delay ALS disease progression.

The Immunoreactivity of PI3K/AKT Pathway After Prenatal Hypoxic Damage

BACKGROUND/AIM

There is no consensus on the effect of hypoxia on neurogenesis. In this study, we investigated the immunoreactivity of BDNF and PI3K/Akt signaling after uterine artery ligation in pregnant rats.

MATERIALS AND METHODS

Unilateral uterine artery ligation was performed at 16 days of gestation (dg). Fetuses from one horn with ligated artery were allocated to the hypoxic group. Immunohistochemistry was performed with primary antibodies; NeuN, BDNF, PI3K, Akt and phospho-Akt (pAkt).

RESULTS

The densities of NeuN- and BDNF-immunoreactive (IR) cells in the cerebral cortex were lower in the hypoxic fetuses than in the controls at 21 dg. The density of PI3K and pAkt-IR cells in the cortex of the hypoxic group significantly decreased. The results in dentate gyrus were similar to the results in the cerebral cortex.

CONCLUSION

Prenatal hypoxia reduced Akt phosphorylation, which affected neuronal survival in the cortex and dentate gyrus.

Perspectives on Epidermal Growth Factor Receptor Regulation in Triple-Negative Breast Cancer: Ligand-Mediated Mechanisms of Receptor Regulation and Potential for Clinical Targeting

Currently, there are no effective targeted therapies for triple-negative breast cancer (TNBC) indicating a critical unmet need for breast cancer patients. Tumors that fall into the triple-negative category of breast cancers do not respond to the targeted therapies currently approved for breast cancer treatment, such as endocrine therapy (tamoxifen, aromatase inhibitors) or human epidermal growth factor receptor-2 (HER2) inhibitors (trastuzumab, lapatinib), because these tumors lack the most common breast cancer markers: estrogen receptor, progesterone receptor, and HER2. While many patients with TNBC respond to chemotherapy, subsets of patients fare poorly and relapse very quickly. Studies indicate that epidermal growth factor receptor (EGFR) is frequently overrepresented in TNBC (>50%), suggesting EGFR could be used as a biomarker and target in breast cancer. While it is clear that this growth factor receptor plays an integral role in TNBC, little is known about the mechanisms of sustained EGFR activation and how to target this protein despite availability of EGFR-targeted inhibitors, suggesting that our understanding of EGFR deregulation in TNBC is incomplete.

Antitumor activity of SAHA, a novel histone deacetylase inhibitor, against murine B cell lymphoma A20 cells in vitro and in vivo

Suberoylanilide hydroxamic acid (SAHA; vorinostat), the second generation of histone deacetylase (HDAC) inhibitor, has been approved for the treatment of cutaneous manifestations of cutaneous T cell lymphoma (CTCL). It has also shown its anticancer activity over a large range of other hematological and solid malignancies, but few studies have been reported in B cell lymphoma. In this study, we aimed to investigate the antitumor activity of SAHA on murine B cell lymphoma cell line A20 cells. We treated A20 cells with different concentrations of SAHA. The effect of SAHA on the proliferation of A20 cells was studied by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium (MTT) assay in vitro; the anti-proliferation activity in vivo was evaluated by proliferating cell nuclear antigen (PCNA) of xenograft tumor tissues through immunocytochemical staining. Apoptosis were detected by Hoechst 33258 staining and Annexin V/propidium iodide (PI) double-labeled cytometry in vitro. The effect of SAHA on cell cycle of A20 cells was studied by a propidium iodide method. Autophagic cell death induced by SAHA was confirmed by transmission electron microscopy (TEM). Angiogenesis marker (CD31) was measured by immunocytochemical staining to investigate the anti-angiogenic effect of SAHA. Western blot was used to detect the expression of signaling pathway factors (phospho-AKT, phospho-ERK, AKT, ERK, Nur77, HIF-1α, and VEGF). Our results showed that SAHA inhibited the proliferation of A20 cells in a time- and dose-dependent manner, induced cell apoptosis and G0/G1 phase arrest of cell cycle, promoted autophagic cell death, and suppressed tumor progress in NCI-A20 cells nude mice xenograft model in vivo. SAHA decreased the activation of AKT (phospho-AKT: p-AKT) and ERK1/2 (phospho-ERK: p-ERK) proteins and inhibited the expression of pro-angiogenic factors (VEGF and HIF-1α), downregulated its downstream signaling factor (Nur77), which might be contributed to the antitumor mechanisms of SAHA.

Long-term artificial sweetener acesulfame potassium treatment alters neurometabolic functions in C57BL/6J mice

With the prevalence of obesity, artificial, non-nutritive sweeteners have been widely used as dietary supplements that provide sweet taste without excessive caloric load. In order to better understand the overall actions of artificial sweeteners, especially when they are chronically used, we investigated the peripheral and central nervous system effects of protracted exposure to a widely used artificial sweetener, acesulfame K (ACK). We found that extended ACK exposure (40 weeks) in normal C57BL/6J mice demonstrated a moderate and limited influence on metabolic homeostasis, including altering fasting insulin and leptin levels, pancreatic islet size and lipid levels, without affecting insulin sensitivity and bodyweight. Interestingly, impaired cognitive memory functions (evaluated by Morris Water Maze and Novel Objective Preference tests) were found in ACK-treated C57BL/6J mice, while no differences in motor function and anxiety levels were detected. The generation of an ACK-induced neurological phenotype was associated with metabolic dysregulation (glycolysis inhibition and functional ATP depletion) and neurosynaptic abnormalities (dysregulation of TrkB-mediated BDNF and Akt/Erk-mediated cell growth/survival pathway) in hippocampal neurons. Our data suggest that chronic use of ACK could affect cognitive functions, potentially via altering neuro-metabolic functions in male C57BL/6J mice.

Impaired hypoxic sensor Siah-1, PHD3, and FIH system in spinal motor neurons of an amyotrophic lateral sclerosis mouse model

We recently reported spinal blood flow-metabolism uncoupling in the Cu/Zn-superoxide dismutase 1 (SOD1)-transgenic (Tg) mouse model of amyotrophic lateral sclerosis (ALS), suggesting relative hypoxia in the spinal cord. However, the hypoxic stress sensor pathway in ALS has not been well studied. In the present work, we examined the temporal and spatial changes of hypoxic stress sensor proteins (Siah-1, PHD3, and FIH) following motor neuron (MN) degeneration in the spinal cord of normoxic ALS mice. The expression of Siah-1 and PHD3 proteins progressively increased in the surrounding glial cells of presymptomatic Tg mice (10 weeks, 10 weeks) compared with the large MN of the anterior horn. In contrast, a significant reduction in Siah-1 and PHD3 protein expression was evident in end-stage ALS mice (18 weeks, 18 weeks). Double-immunofluorescence analysis revealed PHD3 plus Siah-1 double-positive cells in the surrounding glia of symptomatic Tg mice (14-18 weeks), with no change in the large MNs. In contrast, FIH protein expression decreased in the surrounding glial cells of Tg mice at end-stage ALS (18 weeks). The present study suggests a partial loss in the neuroprotective response of spinal MNs in ALS results from a relative hypoxia through the Siah-1, PHD3, and FIH system under normoxic conditions. This response could be an important mechanism of neurodegeneration in ALS.

Impaired response of hypoxic sensor protein HIF-1α and its downstream proteins in the spinal motor neurons of ALS model mice

We have recently reported spinal blood flow-metabolism uncoupling in an amyotrophic lateral sclerosis (ALS) animal model using Cu/Zn-superoxide dismutase 1 (SOD1)-transgenic (Tg) mice, suggesting a relative hypoxia in the spinal cord. However, the hypoxic stress sensor pathway has not been well studied in ALS. Here, we examined temporal and spatial changes of the hypoxic stress sensor proteins HIF-1α and its downstream proteins (VEGF, HO-1, and EPO) during the normoxiccourse of motor neuron (MN) degeneration in the spinal cord of these ALS model mice. We found that HIF-1α protein expression progressively increased both in the anterior large MNs and the surrounding glial cells in Tg mice from early symptomatic 14 week (W) and end stage 18 W. Double immunofluorescence analysis revealed that HIF-1α, plus GFAP and Iba-1 double-positive surrounding glial cells, progressively increased from 14 W to 18 W, although the immunohistochemistry in large MNs did not change. Expression levels of VEGF and HO-1 also showed a progressive increase but were significant only in the surrounding glial cells at 18 W. In contrast, EPO protein expression was decreased in the surrounding glial cells of Tg mice at 18 W. Because HIF1-α serves as an important mediator of the hypoxic response, these findings indicate that MNs lack the neuroprotective response to hypoxic stress through the HIF-1α system, which could be an important mechanism of neurodegeneration in ALS.

Heat shock protein 72 inhibits c-Jun N-terminal kinase 3 signaling pathway via Akt1 during cerebral ischemia

Although recent researches show that Heat Shock Protein 72 (HSP72) plays an important role in neuronal survival, little knowledge is known about the precise mechanisms during cerebral ischemia/reperfusion (I/R). Our present study investigated the neuroprotective mechanisms of HSP72 against ischemic brain injury induced by cerebral I/R. Mild heat shock pretreatment was employed to induce the overexpression of HSP72 by immersing rats into the water bath at 42°C for 20 min before cerebral I/R. HSP72 antisense oligodeoxynucleotides (ODNs) were used to inhibit HSP72 expression by intracerebroventricular infusion once per day for 3 days before cerebral I/R animal model was induced by four-vessel occlusion for 15 min transient ischemia and then reperfused for various time in Sprague-Dawley rats. Immunoprecipitation and immunoblotting were used to detect the expression of the related proteins. HE-staining and TUNEL-staining were carried out to examine the neuronal death of hippocampal CA1 region. Results showed that mild heat shock could increase the phosphorylation of protein kinase B (Akt), inhibit the assembly of MLK3-MKK7-JNK3 signaling module, diminish the phosphorylation of JNK3 and c-Jun, and decrease the activation of caspase-3. Furthermore, mild heat shock could significantly protect neurons against cerebral I/R. Whereas, all of the aforementioned effects of mild heat shock were reversed by HSP72 antisense ODNs. In summary, our results imply that Akt1 activation is involved in the neuroprotection of HSP72 against ischemic brain injury via suppressing JNK3 signaling pathway and provide a new experimental foundation for stroke therapy.

Impaired antioxydative Keap1/Nrf2 system and the downstream stress protein responses in the motor neuron of ALS model mice

The Kelch-like ECH-associated protein 1 (Keap1)/Nuclear erythroid 2-related factor 2 (Nrf2) system is the major cellular defense mechanism under oxidative stress, but the role in motor neuron degeneration under amyotrophic lateral sclerosis (ALS) pathology has not yet been fully elucidated. Here we examined temporal and spatial changes of Keap1, Nrf2, and their downstream stress response proteins heme oxgenase-1 (HO-1), glutathione, thioredoxin (TRX), and heat shock protein 70 (HSP70) throughout the course of motor neuron (MN) degeneration in the spinal cord of ALS model mice. Keap1 protein levels progressively decreased in the MN and anterior lumbar cord of ALS mice to 63% at early symptomatic 14 weeks and 58% at end symptomatic 18 weeks, while Nrf2 dramatically increased in the anterior lumbar cord with accumulation in the MN nucleus to 229% at 14 weeks and 471% at 18 weeks when glial like cells became also positive. In contrast, downstream stress response proteins such as HO-1, glutathione, TRX, and HSP70 showed only a small increase in MN with a significant increase to 149% to 280% in the number of glial-like cells after symptomatic 14 weeks. Our present observation suggests that MN selectively lost inductions of these important downstream protective proteins without regard to the Keap1/Nrf2 system activation, which could be a pivotal mechanism of neurodegenerative processes of ALS.

Impaired SDF1/CXCR4 signaling in glial progenitors derived from SOD1(G93A) mice

Mutations in the superoxide dismutase 1 (SOD1) gene are associated with familial amyotrophic lateral sclerosis (ALS), and the SOD1(G93A) transgenic mouse has been widely used as one animal model for studies of this neurodegenerative disorder. Recently, several reports have shown that abnormalities in neuronal development in other models of neurodegeneration occur much earlier than previously thought. To study the role of mutant SOD1 in glial progenitor biology, we immortalized glial restricted precursors (GRIPs) derived from mouse E11.5 neural tubes of wild-type and SOD1(G93A) mutant mice. Immunocytochemistry using cell lineage markers shows that these cell lines can be maintained as glial progenitors, because they continue to express A2B5, with very low levels of glial fibrillary acidic protein (astrocyte), betaIII-tubulin (neuron), and undetected GalC (oligodendrocyte) markers. RT-PCR and immunoblot analyses indicate that the chemokine receptor CXCR4 is reduced in SOD1(G93A) GRIPs. Subsequently, SOD1(G93A) GRIPs are unable to respond to SDF1alpha to activate ERK1/2 enzymes and the transcription factor CREB. This may be one pathway leading to a reduction in SOD1(G93A) cell migration. These data indicate that the abnormalities in SOD1(G93A) glial progenitor expression of CXCR4 and its mediated signaling and function occur during spinal cord development and highlight nonneuronal (glial) abnormalities in this ALS model.

Reduction of a vascular endothelial growth factor receptor, fetal liver kinase-1, by antisense oligonucleotides induces motor neuron death in rat spinal cord exposed to hypoxia

Vascular endothelial growth factor (VEGF) is reported to play a neuroprotective role through a VEGF receptor, fetal liver kinase-1 (Flk-1) in vitro. We investigated whether reduction of Flk-1 could induce motor neuron loss in rat spinal cord by inhibiting the expression of Flk-1 in rat spinal cord using antisense oligodeoxynucleotides (ODNs) against the Flk-1 receptor. Rat spinal cord was repetitively exposed to 12% hypoxia, and the change of the phosphatidylinositol 3-kinase (PI3-K)/Akt pathway and the mitogen-activated protein kinase kinase (MEK)/extracellular-signal-regulated kinase (ERK) pathway was examined. Intrathecal infusion of Flk-1 antisense ODNs for 7 days suppressed almost completely Flk-1 expression in the lumbar segment of the spinal cord and was followed by a hypoxic challenge with 12% oxygen for 1 h that was repeated for 7 more days. In the lumbar segment, we observed that reduced Flk-1 expression and hypoxic challenge for 7 days resulted in approximately 50% loss of motor neurons, in which the activation of Akt and ERK, that is, increased levels of phosphorylated-Akt and of phosphorylated-ERK by hypoxia, was markedly inhibited. In contrast, the reduction of Flk-1 expression alone did not induce motor neuron loss. These results suggest that VEGF exerts its protective effect on motor neurons against hypoxia-induced toxicity by the Flk-1 receptor through the PI3-K/Akt and the MEK/ERK signaling pathways.

MEK inhibitor, U0126, attenuates cisplatin-induced renal injury by decreasing inflammation and apoptosis

BACKGROUND

Although inflammation and apoptosis are known to play important roles in cisplatin nephrotoxicity, the exact intracellular signaling mechanisms are not well understood. Recent reports that extracellular signal-regulated kinase (ERK1/2) pathway mediates cisplatin-induced caspase activation and apoptosis in cultured renal tubular cells led us to investigate the effect of MAPK/ERK kinase (MEK) inhibitor, an immediate upstream of ERK1/2 in cisplatin-induced acute renal failure (ARF) in mice.

METHODS

The effect of MEK/ERK1/2 inhibition on kidney tumor necrosis factor-alpha (TNF-alpha (gene expression, inflammation, the activation of tissue caspases, and apoptosis were examined in addition to its effects on renal function and histology in cisplatin-induced ARF in mice.

RESULTS

Pretreatment of MEK inhibitor, U0126, decreased ERK1/2 phosphorylation following cisplatin administration with significant functional and histologic protection. This beneficial effect was accompanied by decrease in TNF-alpha gene expression level and inflammation, as well as in caspase 3 activity and apoptosis.

CONCLUSION

These data provide evidence that ERK1/2 pathway functions as an upstream signal for TNF-alpha-mediated inflammation and caspase 3-mediated apoptosis in cisplatin-induced ARF in mice and suggest that ERK1/2 can be a novel therapeutic target in cisplatin nephrotoxicity.