Astrocyte Mitochondria in White-Matter Injury

This review summarizes the diverse structure and function of astrocytes to describe the bioenergetic versatility required of astrocytes that are situated at different locations. The intercellular domain of astrocyte mitochondria defines their roles in supporting and regulating astrocyte-neuron coupling and survival against ischemia. The heterogeneity of astrocyte mitochondria, and how subpopulations of astrocyte mitochondria adapt to interact with other glia and regulate axon function, require further investigation. It has become clear that mitochondrial permeability transition pores play a key role in a wide variety of human diseases, whose common pathology may be based on mitochondrial dysfunction triggered by Ca²⁺ and potentiated by oxidative stress. Reactive oxygen species cause axonal degeneration and a reduction in axonal transport, leading to axonal dystrophies and neurodegeneration including Alzheimer’s disease, amyotrophic lateral sclerosis, Parkinson’s disease, and Huntington’s disease. Developing new tools to allow better investigation of mitochondrial structure and function in astrocytes, and techniques to specifically target astrocyte mitochondria, can help to unravel the role of mitochondrial health and dysfunction in a more inclusive context outside of neuronal cells. Overall, this review will assess the value of astrocyte mitochondria as a therapeutic target to mitigate acute and chronic injury in the CNS.

     

Development of Neoseiulus womersleyi (Schicha) and Euseius ovalis (Evans) feeding on four tetranychid mites (Acari: Phytoseiidae,Tetranychidae) and pollen

The development of the predatory mites, Neoseiulus womersleyi (Schicha) and Euseius ovalis (Evans), feeding on four tetranychid mites (Tetranychus urticae, Tetranychus kanzawai, Oligonychus mangiferus, Panonychus citri), maize pollen or Chinese loofah pollen was studied at 25 °C. Immature stages of N. womersleyi feeding on T. urticae and T. kanzawai had shorter developmental duration (4.71 and 5.02 days for females, 4.77 and 5.19 days for males, respectively) than those feeding on other food sources. Immature stages of E. ovalis females feeding on O. mangiferus and T. urticae developed in 4.99 and 5.13 days, respectively, the shortest developmental duration measured. Immature stages of E. ovalis males feeding on O. mangiferus and T. urticae developed in 5.12 and 5.37 days, respectively. The longevity of N. womersleyi males (13.31 to 14.51 days) and females (17.67 to 21.81 days) feeding on T. urticae, T. kanzawai or maize pollen was longer than the longevity of N. womersleyi feeding on O. mangiferus, P. citri or loofah pollen. E. ovalis males (12.91 to 16.74 days) and females (16.24 to 23.77 days) feeding on O. mangiferus, T. urticae or maize pollen lived longer than E. ovalis males and females feeding on T. kanzawai, P. citri or loofah pollen.     

Broad-spectrum antioxidant peptides derived from His residue-containing sequences present in human paraoxonase 1

Hydroxyl or peroxyl radicals and hypochlorous acid (HOCl) are known to cause the oxidation of lipoproteins. Here, we examined Cu²⁺-binding property of paraoxonase 1 (PON1), and antioxidant actions of peptides, resembling His residue-containing sequences in PON1, against oxidations by Cu²⁺, peroxyl radicals or HOCl. When Cu²⁺-binding property of PON1 was examined spectrophotometrically, the maximal Cu²⁺ binding was achieved at 1:1 molar ratio of PON1: Cu²⁺. Additionally, Cu²⁺-catalyzed oxidative inactivation of PON1 was prevented by Ca²⁺-depleted PON1 at 1:1 ratio, but not diethylpyrocarbonate (DEPC)-modified PON1, suggesting the participation of His residue in Cu²⁺-binding. When His-containing peptides were examined for antioxidant actions, those with either His residue at N-terminal position 2 or 3, or His-Pro sequence at C-terminal remarkably prevented Cu²⁺-mediated low density lipoprotein (LDL) oxidation and PON1 inactivation. Especially, FHKALY, FHKY or NHP efficiently prevented Cu²⁺-induced LDL oxidation (24 h), indicating a tight binding of Cu²⁺ by peptides. In support of this, the peptide/Cu²⁺ complexes exhibited a superoxide-scavenging activity. Separately, in oxidations by 2,2'-azobis-2-amidinopropane hydrochloride or HOCl, the presence of Tyrosine (Tyr) or Cysteine (Cys) residue markedly enhanced antioxidant action of His-containing peptides. These results indicate that His-containing peptides with Tys or Cys residues correspond to broad spectrum antioxidants in oxidation models employing Cu²⁺, 2,2'-azobis-2-amidinopropane hydrochloride (AAPH) or HOCl.     

Ouabain activates the Na-K-ATPase signalosome to induce autosomal dominant polycystic kidney disease cell proliferation

The Na-K-ATPase is part of a cell signaling complex, the Na-K-ATPase signalosome, which upon activation by the hormone ouabain regulates the function of different cell types. We previously showed that ouabain induces proliferation of epithelial cells derived from renal cysts of patients with autosomal dominant polycystic kidney disease (ADPKD cells). Here, we investigated the signaling pathways responsible for mediating the effects of ouabain in these cells. Incubation of ADPKD cells with ouabain, in concentrations similar to those found in blood, stimulated phosphorylation of the epidermal growth factor receptor (EGFR) and promoted its association to the Na-K-ATPase. In addition, ouabain activated the kinase Src, but not the related kinase Fyn. Tyrphostin AG1478 and PP2, inhibitors of EGFR and Src, respectively, blocked ouabain-dependent ADPKD cell proliferation. Treatment of ADPKD cells with ouabain also caused phosphorylation of the caveolar protein caveolin-1, and disruption of cell caveolae with methyl-β-cyclodextrin prevented Na-K-ATPase-EGFR interaction and ouabain-induced proliferation of the cells. Downstream effects of ouabain in ADPKD cells included activation of B-Raf and MEK and phosphorylation of the extracellular regulated kinase ERK, which translocated into the ADPKD cell nuclei. Finally, ouabain reduced expression of the cyclin-dependent kinase inhibitors p21 and p27, which are suppressors of cell proliferation. Different from ADPKD cells, ouabain showed no significant effect on B-Raf, p21, and p27 in normal human kidney epithelial cells. Altogether, these results identify intracellular pathways of ouabain-dependent Na-K-ATPase-mediated signaling in ADPKD cells, including EGFR-Src-B-Raf-MEK/ERK, and establish novel mechanisms involved in ADPKD cell proliferation.     

Suprafenacine,an Indazole-Hydrazide Agent,Targets Cancer Cells Through Microtubule Destabilization

Microtubules are a highly validated target in cancer therapy. However, the clinical development of tubulin binding agents (TBA) has been hampered by toxicity and chemoresistance issues and has necessitated the search for new TBAs. Here, we report the identification of a novel cell permeable, tubulin-destabilizing molecule - 4,5,6,7-tetrahydro-1H-indazole-3-carboxylic acid [1p-tolyl-meth-(E)-ylidene]-hydrazide (termed as Suprafenacine, SRF). SRF, identified by in silico screening of annotated chemical libraries, was shown to bind microtubules at the colchicine-binding site and inhibit polymerization. This led to G₂/M cell cycle arrest and cell death via a mitochondria-mediated apoptotic pathway. Cell death was preceded by loss of mitochondrial membrane potential, JNK - mediated phosphorylation of Bcl-2 and Bad, and activation of caspase-3. Intriguingly, SRF was found to selectively inhibit cancer cell proliferation and was effective against drug-resistant cancer cells by virtue of its ability to bypass the multidrug resistance transporter P-glycoprotein. Taken together, our results suggest that SRF has potential as a chemotherapeutic agent for cancer treatment and provides an alternate scaffold for the development of improved anti-cancer agents.     

Morphology of the archaellar motor and associated cytoplasmic cone in Thermococcus kodakaraensis

Archaeal swimming motility is driven by archaella: rotary motors attached to long extracellular filaments. The structure of these motors, and particularly how they are anchored in the absence of a peptidoglycan cell wall, is unknown. Here, we use electron cryotomography to visualize the archaellar basal body in vivo in Thermococcus kodakaraensis KOD1. Compared to the homologous bacterial type IV pilus (T4P), we observe structural similarities as well as several unique features. While the position of the cytoplasmic ATPase appears conserved, it is not braced by linkages that extend upward through the cell envelope as in the T4P, but rather by cytoplasmic components that attach it to a large conical frustum up to 500 nm in diameter at its base. In addition to anchoring the lophotrichous bundle of archaella, the conical frustum associates with chemosensory arrays and ribosome‐excluding material and may function as a polar organizing center for the coccoid cells.