Proteolytic events in cryonecrotic cell death: Proteolytic activation of endonuclease P23

Cathepsin D deficiency delays central nervous system myelination by inhibiting proteolipid protein trafficking from late endosome/lysosome to plasma membrane

This study aimed to investigate the role of cathepsin D (CathD) in central nervous system (CNS) myelination and its possible mechanism. By using CathD knockout mice in conjunction with immunohistochemistry, immunocytochemistry and western blot assays, the myelination of the CNS and the development of oligodendrocyte lineage cells in vivo and in vitro were observed. Endocytosis assays, real-time-lapse experiments and total internal reflection fluorescence microscopy were used to demonstrate the location and movement of proteolipid protein in oligodendrocyte lineage cells. In addition, the relevant molecular mechanism was explored by immunoprecipitation. The increase in Fluoromyelin Green staining and proteolipid protein expression was not significant in the corpus callosum of CathD-/- mice at the age of P11, P14 and P24. Proteolipid protein expression was weak at each time point and was mostly accumulated around the nucleus. The number of oligodendrocyte lineage cells (olig2+) and mature oligodendrocytes (CC1+) significantly decreased between P14 and P24. In the oligodendrocyte precursor cell culture of CathD-/- mice, the morphology of myelin basic protein-positive mature oligodendrocytes was simple while oligodendrocyte precursor cells showed delayed differentiation into mature oligodendrocytes. Moreover, more proteolipid protein gathered in late endosomes/lysosomes (LEs/Ls) and fewer reached the plasma membrane. Immunohistochemistry and immunoelectron microscopy analysis showed that CathD, proteolipid protein and VAMP7 could bind with each other, whereas VAMP7 and proteolipid protein colocalized with CathD in late endosome/lysosome. The findings of this paper suggest that CathD may have an important role in the myelination of CNS, presumably by altering the trafficking of proteolipid protein.

Docosahexanoic acid antagonizes TNF-α-induced necroptosis by attenuating oxidative stress, ceramide production, lysosomal dysfunction, and autophagic features

OBJECTIVE

It was previously reported that docosahexanoic acid (DHA) reduces TNF-α-induced necrosis in L929 cells. However, the mechanisms underlying this reduction have not been investigated. The present study was designed to investigate cellular and biochemical mechanisms underlying the attenuation of TNF-α-induced necroptosis by DHA in L929 cells.

METHODS

L929 cells were pre-treated with DHA prior to exposure to TNF-α, zVAD, or Necrostatin-1 (Nec-1). Cell death and survival were assessed by MTT and caspase activity assays, and microscopic visualization. Reactive oxygen species (ROS) were measured by flow cytometry. C16- and C18-ceramides were measured by mass spectrometry. Lysosomal membrane permeabilization (LMP) was evaluated by fluorescence microscopy and flow cytometry using Acridine Orange. Cathepsin L activation was evaluated by immunoblotting and fluorescence microscopy. Autophagy was assessed by immunoblotting of LC3-II and Beclin.

RESULTS

Exposure of L929 cells to TNF-α alone for 24 h induced necroptosis, as evidenced by the inhibition of cell death by Nec-1, absence of caspase-3 activity and Lamin B cleavage, and morphological analysis. DHA attenuated multiple biochemical events associated with TNF-α-induced necroptosis, including ROS generation, ceramide production, lysosomal dysfunction, cathepsin L activation, and autophagic features. DHA also attenuated zVAD-induced necroptosis but did not attenuate the enhanced apoptosis and necrosis induced by the combination of TNF-α with Actinomycin D or zVAD, respectively, suggesting that its protective effects might be limited by the strength of the cell death insult induced by TNF-α.

CONCLUSIONS

DHA effectively attenuates TNF-α-induced necroptosis and autophagy, most likely via its ability to inhibit TNF-α-induced sphingolipid metabolism and oxidative stress. These results highlight the role of this Omega-3 fatty acid in antagonizing inflammatory cell death.

Multimodal liver-directed management of neuroendocrine hepatic metastases

A preponderance of patients with neuroendocrine tumors (NETs) will experience hepatic metastases during the course of their disease. Many diagnoses of NETs are made only after the neoplasms have spread from their primary gastroenteropancreatic sites to the liver. This paper reviews current evidence-based treatments for neuroendocrine hepatic metastases, encompassing surgery, hepatic artery embolization (HAE) and chemoembolization (HACE), radioembolization, hepatic artery infusion (HAI), thermal ablation (radiofrequency, microwave, and cryoablation), alcohol ablation, and liver transplantation as therapeutic modalities. Consideration of a multidisciplinary approach to liver-directed therapy is strongly encouraged to limit morbidity and mortality in this patient population.