Molecular characterization and functional analysis of apoptosis-inducing factor (AIF) in palmitic acid-induced apoptosis in Ctenopharyngodon idellus kidney (CIK) cells

Caspase-dependent apoptosis in Riboflavin Transporter Deficiency iPSCs and derived motor neurons

Riboflavin Transporter Deficiency (RTD) is a rare genetic, childhood-onset disease. This pathology has a relevant neurological involvement, being characterized by motor symptoms, ponto-bulbar paralysis and sensorineural deafness. Such clinical presentation is associated with muscle weakness and motor neuron (MN) degeneration, so that RTD is considered part of the MN disease spectrum. Based on previous findings demonstrating energy dysmetabolism and mitochondrial impairment in RTD induced Pluripotent Stem cells (iPSCs) and iPSC-derived MNs, here we address the involvement of intrinsic apoptotic pathways in disease pathogenesis using these patient-specific in vitro models by combined ultrastructural and confocal analyses. We show impaired neuronal survival of RTD iPSCs and MNs. Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM) documents severe alterations in patients' cells, including deranged mitochondrial ultrastructure, and altered plasma membrane and nuclear organization. Occurrence of aberrantly activated apoptosis is confirmed by immunofluorescence and TUNEL assays. Overall, our work provides evidence of a role played by mitochondrial dysfunction in RTD, and identifies neuronal apoptosis as a contributing event in disease pathogenesis, indicating intrinsic apoptosis pathways as possible relevant targets for more effective therapeutical approaches.

Eicosapentaenoic acid mitigates palmitic acid-induced heat shock response, inflammation and repair processes in fish intestine

Understanding the metabolic effects of fatty acids on fish intestine is critical to the substitution of fish oil with vegetable oils in aquaculture. In this study, the effects of eicosapentaenoic acid (EPA) and palmitic acid (PA) on fish intestine were evaluated in vitro and in vivo. As the first step for in vitro study, an intestinal cell line (SPIF) was established from silver pomfret (Pampus argenteus). Thereafter, the effects of EPA and PA on cell viability, prostaglandin E2 (PGE2) production, and the expression of genes related to heat shock response, inflammation, extracellular matrix (ECM) formation and degradation were examined in SPIF cells. Finally, these metabolic effects of EPA and PA on the intestine were examined in zebrafish (Danio rerio) larvae. Results showed that all tested fatty acids (PA, oleic acid, linoleic acid, α-linolenic acid, arachidonic acid, and docosahexaenoic acid) except EPA reduced SPIF viability to distinct degrees at the same concentrations. PA decreased SPIF viability accompanied by an increase in PGE2 level. Meanwhile, PA increased the expression of genes related to heat shock response (grp78, grp94, hsp70, and hsp90) and inflammation (nf-κb, il-1β, and cox2). Furthermore, PA reduced the expression of collagen type I (col1a1a and col1a1b) and extracellular matrix (ECM) degradation-related gene mmp2, while up-regulating timp2 mRNA expression. In vivo, PA also increased hsp70, il-1β, and cox2 mRNA levels and limited the expression of collagen type I in the larval zebrafish intestine. Interestingly, the combination of EPA and PA partially recovered the PA-induced changes in cell viability, PGE2 production, and mRNA expression in vitro and in vivo. These results suggest that PA may result in heat shock and inflammatory responses, as well as alter ECM formation and degradation in fish intestine, while EPA could at least partially mitigate these negative effects caused by PA.

Notoginsenoside R1 Ameliorates Cardiac Lipotoxicity Through AMPK Signaling Pathway

Aims: Cardiac lipotoxicity is the common consequence of lipid metabolism disorders in cardiomyocytes during development of heart failure (HF). Adenosine 5'monophosphate-activated protein kinase (AMPK) acts as an energy sensor and has a beneficial effect in reducing lipotoxicity. Notoginsenoside R1 (NGR1) is extracted from the traditional Chinese medicine Panax notoginseng (Burkill) F.H.Chen (P. notoginseng) and has definite cardioprotective effects. However, whether NGR1 can attenuate HF by mitigating lipotoxicity has not been elucidated yet. This study aimed to explore whether NGR1 plays a protective role against HF by ameliorating cardiac lipotoxicity via the AMPK pathway. Methods: In this study, HF mice model was established by left anterior descending (LAD) ligation. palmitic acid (PA) stimulated H9C2 cell model was applied to clarify the effects and potential mechanism of NGR1 on lipotoxicity. In vivo, NGR1 (7.14 mg/kg/days) and positive drug (simvastatin: 2.9 mg/kg/days) were orally administered for 14 days. Echocardiography was applied to assess heart functions. Lipid levels were measured by Enzyme-linked immunosorbent assay (ELISA) and key proteins in the AMPK pathway were detected by western blots. In vitro, NGR1 (40 μmol/L) or Compound C (an inhibitor of AMPK, 10 μmol/L) was co-cultured with PA stimulation for 24 h in H9C2 cells. CCK-8 assay was used to detect cell viability. Key lipotoxicity-related proteins were detected by western blots and the LipidTOX™ neutral lipid stains were used to assess lipid accumulation. In addition, Apoptosis was assessed by Hoechst/PI staining. Results: NGR1 could significantly improve the cardiac function and myocardial injury in mice with HF and up-regulate the expression of p-AMPK. Impressively, NGR1 inhibited the synthesis of diacylglycerol (DAG) and ceramide and promoted fatty acid oxidation (FAO) in vivo. Moreover, NGR1 significantly promoted expression of CPT-1A, the key enzyme in FAO pathway, and down-regulated the expression of GPAT and SPT, which were the key enzymes catalyzing production of DAG and ceramide. In vitro experiments showed that NGR1 could significantly attenuate lipid accumulation in PA-induced H9C2 cells and the Hoechst/PI staining results showed that NGR1 ameliorated lipotoxicity-induced apoptosis in PA-stimulated H9C2 cell model. Furthermore, co-treatment with inhibitor of AMPK abrogated the protective effects of NGR1. The regulative effects of NGR1 on lipid metabolism were also reversed by AMPK inhibitor. Conclusion: NGR1 could significantly improve the heart function of mice with HF and reduce cardiac lipotoxicity. The cardio-protective effects of NGR1 are mediated by the activation of AMPK pathway.

Apoptosis-Inducing Factor 2 (AIF-2) Mediates a Caspase-Independent Apoptotic Pathway in the Tropical Sea Cucumber (Holothuria leucospilota)

Apoptosis, also known as programmed cell death, is a biological process that is critical for embryonic development, organic differentiation, and tissue homeostasis of organisms. As an essential mitochondrial flavoprotein, the apoptosis-inducing factor (AIF) can directly mediate the caspase-independent mitochondrial apoptotic pathway. In this study, we identified and characterized a novel AIF-2 (HlAIF-2) from the tropical sea cucumber Holothuria leucospilota. HlAIF-2 contains a conserved Pyr_redox_2 domain and a putative C-terminal nuclear localization sequence (NLS) but lacks an N-terminal mitochondrial localization sequence (MLS). In addition, both NADH- and FAD-binding domains for oxidoreductase function are conserved in HlAIF-2. HlAIF-2 mRNA was ubiquitously detected in all tissues and increased significantly during larval development. The transcript expression of HlAIF-2 was significantly upregulated after treatment with CdCl₂, but not the pathogen-associated molecular patterns (PAMPs) in primary coelomocytes. In HEK293T cells, HlAIF-2 protein was located in the cytoplasm and nucleus, and tended to transfer into the nucleus by CdCl₂ incubation. Moreover, there was an overexpression of HlAIF-2-induced apoptosis in HEK293T cells. As a whole, this study provides the first evidence for heavy metal-induced apoptosis mediated by AIF-2 in sea cucumbers, and it may contribute to increasing the basic knowledge of the caspase-independent apoptotic pathway in ancient echinoderm species.