BBA - Molecular Basis of Disease (v.1792, #11)

Can cellular models revolutionize drug discovery in Parkinson's disease? by Birgitt Schüle; Renee A. Reijo Pera; J. William Langston (1043-1051).
The study of mechanisms that underlie Parkinson's disease (PD), as well as translational drug development, has been hindered by the lack of appropriate models. Both cell culture systems and animal models have limitations, and to date none faithfully recapitulate all of the clinical and pathological phenotypes of the disease. In this review we examine the various cell culture model systems of PD, with a focus on different stem cell models that can be used for investigating disease mechanisms as well as drug discovery for PD. We conclude with a discussion of recent discoveries in the field of stem cell biology that have led to the ability to reprogram somatic cells to a pluripotent state via the use of a combination of genetic factors; these reprogrammed cells are termed “induced pluripotent stem cells” (iPSCs). This groundbreaking technique allows for the derivation of patient-specific cell lines from individuals with sporadic forms of PD and also those with known disease-causing mutations. Such cell lines have the potential to serve as a human cellular model of neurodegeneration and PD when differentiated into dopaminergic neurons. The hope is that these iPSC-derived dopaminergic neurons can be used to replicate the key molecular aspects of neural degeneration associated with PD. If so, this approach could lead to transformative new tools for the study of disease mechanisms. In addition, such cell lines can be potentially used for high-throughput drug screening. While not the focus of this review, ultimately it is envisioned that techniques for reprogramming of somatic cells may be optimized to a point sufficient to provide potential new avenues for stem cell-based restorative therapies.
Keywords: Parkinson's disease; Neurodegeneration; iPSC; Nuclear reprogramming; Cellular disease model;

Frataxin deficiency induces Schwann cell inflammation and death by Chunye Lu; Robert Schoenfeld; Yuxi Shan; Hsing-Jo Tsai; Bruce Hammock; Gino Cortopassi (1052-1061).
Mutations in the frataxin gene cause dorsal root ganglion demyelination and neurodegeneration, which leads to Friedreich's ataxia. However the consequences of frataxin depletion have not been measured in dorsal root ganglia or Schwann cells. We knocked down frataxin in several neural cell lines, including two dorsal root ganglia neural lines, 2 neuronal lines, a human oligodendroglial line (HOG) and multiple Schwann cell lines and measured cell death and proliferation. Only Schwann cells demonstrated a significant decrease in viability. In addition to the death of Schwann cells, frataxin decreased proliferation in Schwann, oligodendroglia, and slightly in one neural cell line. Thus the most severe effects of frataxin deficiency were on Schwann cells, which enwrap dorsal root ganglia neurons. Microarray of frataxin-deficient Schwann cells demonstrated strong activations of inflammatory and cell death genes including interleukin-6 and Tumor Necrosis Factor which were confirmed at the mRNA and protein levels. Frataxin knockdown in Schwann cells also specifically induced inflammatory arachidonate metabolites. Anti-inflammatory and anti-apoptotic drugs significantly rescued frataxin-dependent Schwann cell toxicity. Thus, frataxin deficiency triggers inflammatory changes and death of Schwann cells that is inhibitable by inflammatory and anti-apoptotic drugs.
Keywords: Friedreich's ataxia (FRDA); Dorsal root ganglia (DRG) neuron; Schwann cells; Inflammatory response; siRNA; Frataxin;

Loss of Kupffer cells in diet-induced obesity is associated with increased hepatic steatosis, STAT3 signaling, and further decreases in insulin signaling by Alicia H. Clementi; Allison M. Gaudy; Nico van Rooijen; Robert H. Pierce; Robert A. Mooney (1062-1072).
While adipose tissue-associated macrophages contribute to development of chronic inflammation and insulin resistance of obesity, little is known about the role of hepatic Kupffer cells in this environment. Here we address the impact of Kupffer cell ablation using clodronate-encapsulated liposome depletion in a diet-induced obese (DIO) and insulin resistant mouse model. Hepatic expression of macrophage markers measured by realtime RT-PCR remained unaltered in DIO mice despite characteristic expansion of adipose tissue-associated macrophages. DIO mouse livers displayed increased expression of alternative activation markers but unaltered proinflammatory cytokine expression when compared to lean mice. Kupffer cell ablation reduced hepatic anti-inflammatory cytokine IL-10 mRNA expression in lean and DIO mice by 95% and 84%, respectively. Despite decreased hepatic IL-6 gene expression after ablation in lean and DIO mice, hepatic STAT3 phosphorylation, Socs3 and acute phase protein mRNA expression increased. Kupffer cell ablation in DIO mice resulted in additional hepatic triglyceride accumulation and a 30–40% reduction in hepatic insulin receptor autophosphorylation and Akt activation. Implicating systemic loss of IL-10, high-fat-fed IL-10 knockout mice also displayed increased hepatic STAT3 signaling and hepatic triglyceride accumulation. Insulin signaling was not altered, however. In conclusion, Kupffer cells are a major source of hepatic IL-10 expression, the loss of which is associated with increased STAT3-dependent signaling and steatosis. One or more additional factors appear to be required, however, for the Kupffer cell-dependent protective effect on insulin receptor signaling in DIO mice.
Keywords: Kupffer cell; Macrophage; Diet-induced obesity; Inflammation; Steatosis;

Real-time bioluminescence imaging of polycythemia vera development in mice by Yanhong Ma; Shuxia Zhao; Joe Zhu; Kimberly A. Bettano; Xianlu Qu; C. Gary Marshall; Jonathan R. Young; Nancy E. Kohl; Martin L. Scott; Weisheng Zhang; Yuxun Wang (1073-1079).
Polycythemia vera (PV) is a myeloproliferative disorder involving hematopoietic stem cells. A recurrent somatic missense mutation in JAK2 (JAK2V617F) is thought to play a causal role in PV. Therefore, targeting Jak2 will likely provide a molecular mechanism-based therapy for PV. To facilitate the development of such new and specific therapeutics, a suitable and well-characterized preclinical animal model is essential. Although several mouse models of PV have been reported, the spatiotemporal kinetics of PV formation and progression has not been studied. To address this, we created a bone marrow transplant mouse model that co-expresses mutant Jak2 and luciferase 2 (Luc2) genes. Bioluminescent imaging (BLI) was used to visualize disease cells and analyze the kinetics of PV development in vivo. To better understand the molecular mechanism of PV, we generated mice carrying a kinase inactive mutant Jak2 (Jak2K882E), demonstrating that the PV disease was dependent on constitutive activation of the Jak2 kinase activity. We further showed that the Jak2V617F mutation caused increased stem cell renewal activity and impaired cell differentiation, which was at least in part due to deregulated transcriptional programming. The Jak2V617F–Luc2 PV mice will be a useful preclinical model to characterize novel JAK2 inhibitors for the treatment of PV.
Keywords: Polycythemia vera; Mouse model; Jak2; Bioluminescent imaging; Micro-CT;

Enhancement in liver SREBP-1c/PPAR-α ratio and steatosis in obese patients: Correlations with insulin resistance and n-3 long-chain polyunsaturated fatty acid depletion by Paulina Pettinelli; Talía del Pozo; Julia Araya; Ramón Rodrigo; A. Verónica Araya; Gladys Smok; Attila Csendes; Luis Gutierrez; Jorge Rojas; Owen Korn; Fernando Maluenda; Juan C. Diaz; Guillermo Rencoret; Italo Braghetto; Jaime Castillo; Jaime Poniachik; Luis A. Videla (1080-1086).
Sterol receptor element-binding protein-1c (SREBP-1c) and peroxisome proliferator-activated receptor-α (PPAR-α) mRNA expression was assessed in liver as signaling mechanisms associated with steatosis in obese patients. Liver SREBP-1c and PPAR-α mRNA (RT-PCR), fatty acid synthase (FAS) and carnitine palmitoyltransferase-1a (CPT-1a) mRNA (real-time RT-PCR), and n-3 long-chain polyunsaturated fatty acid (LCPUFA)(GLC) contents, plasma adiponectin levels (RIA), and insulin resistance (IR) evolution (HOMA) were evaluated in 11 obese patients who underwent subtotal gastrectomy with gastro-jejunal anastomosis in Roux-en-Y and 8 non-obese subjects who underwent laparoscopic cholecystectomy (controls). Liver SREBP-1c and FAS mRNA levels were 33% and 70% higher than control values (P  < 0.05), respectively, whereas those of PPAR-α and CPT-1a were 16% and 65% lower (P  < 0.05), respectively, with a significant 62% enhancement in the SREBP-1c/PPAR-α ratio. Liver n-3 LCPUFA levels were 53% lower in obese patients who also showed IR and hipoadiponectinemia over controls (P  < 0.05). IR negatively correlated with both the hepatic content of n-3 LCPUFA (r  = − 0.55; P  < 0.01) and the plasma levels of adiponectin (r  = − 0.62; P  < 0.005). Liver SREBP-1c/PPAR-α ratio and n-3 LCPUFA showed a negative correlation (r  = − 0.48; P  < 0.02) and positive associations with either HOMA (r  = 0.75; P  < 0.0001) or serum insulin levels (r  = 0.69; P  < 0.001). In conclusion, liver up-regulation of SREBP-1c and down-regulation of PPAR-α occur in obese patients, with enhancement in the SREBP-1c/PPAR-α ratio associated with n-3 LCPUFA depletion and IR, a condition that may favor lipogenesis over FA oxidation thereby leading to steatosis.
Keywords: Obesity; Liver steatosis; Sterol receptor element binding protein-1c; Peroxisome proliferator activated receptor-α; Insulin resistance;

Failure of the feeding response to fasting in carnitine-deficient juvenile visceral steatosis (JVS) mice: Involvement of defective acyl-ghrelin secretion and enhanced corticotropin-releasing factor signaling in the hypothalamus by Takeo Sakoguchi; Masahisa Horiuchi; Akihiro Asakawa; Miharu Ushikai; Goichiro Yoshida; Mineko Fujimiya; Ikuo Kato; Masamitsu Nakazato; Toru Takeuchi; Takeyori Saheki; Akio Inui (1087-1093).
Carnitine-deficient juvenile visceral steatosis (JVS) mice, suffering from fatty acid metabolism abnormalities, have reduced locomotor activity after fasting. We examined whether JVS mice exhibit specific defect in the feeding response to fasting, a key process of anti-famine homeostatic mechanism. Carnitine-deficient JVS mice showed grossly defective feeding response to 24 h-fasting, with almost no food intake in the first 4 h, in marked contrast to control animals. JVS mice also showed defective acyl-ghrelin response to fasting, less suppressed leptin, and seemingly normal corticotropin-releasing factor (CRF) expression in the hypothalamus despite markedly increased plasma corticosterone. The anorectic response was ameliorated by intraperitoneal administration of carnitine or acyl-ghrelin, with decreased CRF expression. Intracerebroventricular treatment of CRF type 2 receptor antagonist, anti-sauvagine-30, recovered the defective feeding response of 24 h-fasted JVS mice. The defective feeding response to fasting in carnitine-deficient JVS mice is due to the defective acyl-ghrelin and enhanced CRF signaling in the hypothalamus through fatty acid metabolism abnormalities. In this animal model, carnitine normalizes the feeding response through an inhibition of CRF.
Keywords: Anti-famine homeostatic mechanism; Fatty acid metabolism abnormality; Ghrelin; Hypothalamus–pituitary–adrenal axis;