Inhibition of VHL by VH298 Accelerates Pexophagy by Activation of HIF-1α in HeLa Cells.

Autophagy is a pivotal biological process responsible for maintaining the homeostasis of intracellular organelles. Yet the molecular intricacies of peroxisomal autophagy (pexophagy) remain largely elusive. From a ubiquitin-related chemical library for screening, we identified several inhibitors of the Von Hippel-Lindau (VHL) E3 ligase, including VH298, thereby serving as potent inducers of pexophagy. In this study, we observed that VH298 stimulates peroxisomal degradation by ATG5 dependently and escalates the ubiquitination of the peroxisomal membrane protein ABCD3. Interestingly, the ablation of NBR1 is similar to the curtailed peroxisomal degradation in VH298-treated cells. We also found that the pexophagy induced by VH298 is impeded upon the suppression of gene expression by the translation inhibitor cycloheximide. Beyond VHL inhibition, we discovered that roxadustat, a direct inhibitor of HIF-α prolyl hydroxylase, is also a potent inducer of pexophagy. Furthermore, we found that VH298-mediated pexophagy is blocked by silencing HIF-1α. In conclusion, our findings suggest that VH298 promotes pexophagy by modulating VHL-mediated HIF-α transcriptional activity.

Robust Symbol Timing Synchronization for Initial Access under LEO Satellite Channel.

This paper proposes a robust symbol timing synchronization scheme for return link initial access based on the Digital Video Broadcasting-Return Channel via Satellite 2nd generation (DVB-RCS2) system for the Low Earth Orbit (LEO) satellite channel. In most cases, the feedforward estimator structure is considered for implementing Time Division Multiple Access (TDMA) packet demodulators such as the DVB-RCS2 system. More specifically, the Non-Data-Aided (NDA) approach, without using any kind of preamble, pilot, and postamble symbols, is applicable for fine symbol timing synchronization. However, it hinders the improvement in estimation accuracy, especially when dealing with short packet lengths during the initial access from the User Terminal (UT) to the Gateway (GW). Moreover, when a UT sends a short random access packet for initial access or resource request to the LEO satellite channel, the conventional schemes suffer from a large Doppler error depending on UT's location in a beam and satellite velocity. To ameliorate these problems, we propose a novel symbol timing synchronization algorithm for GW, and its advantage is confirmed through computer simulation.

Curcuma phaeocaulis Inhibits NLRP3 Inflammasome in Macrophages and Ameliorates Nanoparticle-Induced Airway Inflammation in Mice.

The activation of NLRP3 results in the assembly of inflammasome that regulates caspase-1 activation and the subsequent secretion of bioactive interleukin (IL)-1ß. Excessive activation of the NLRP3 inflammasome is mechanistically linked to diverse pathophysiological conditions, including airway inflammation. Here, we discovered that Curcuma phaeocaulis can suppress caspase-1 activation and processing of pro-IL-1ß into mature cytokine in macrophages stimulated with NLRP3 inflammasome activators, such as SiO2 or TiO2 nanoparticles. Furthermore, in the bronchoalveolar lavage fluids of animals administered the nanoparticles, the in vitro effects of C. phaeocaulis translated into a decrease in IL-1ß levels and cell infiltration. Demethoxycurcumin (DMC) and curcumin were found to be responsible for the inflammasome inhibitory activity of C. phaeocaulis. Interestingly, in contrast to the previously reported higher antioxidant- and NFκB-inhibitory activities of curcumin, DMC exhibited approximately two-fold stronger potency than curcumin against nanoparticle induced activation of NLRP3 inflammasome. In the light of these results, both compounds seem to act independently of their antioxidant- and NFκB-inhibitory properties. Although how C. phaeocaulis inhibits nanoparticle-activated NLRP3 inflammasome remains to be elucidated, our results provide a basis for further research on C. phaeocaulis extract as an anti-inflammatory agent for the treatment of disorders associated with excessive activation of NLRP3 inflammasome.

Identification and characterization of saikosaponins as antagonists of transient receptor potential A1 channel.

Neuropathic pain is associated with an increased sensitivity to painful stimuli or abnormal sensitivity to otherwise innocuous stimuli. However, in addition to adverse effects, currently available drugs have shown limited response in patients with neuropathic pain, which provides a rationale to explore new drug classes acting on novel targets and with better efficacy and safety profiles. Here, we found that saikosaponins potently inhibit agonist-induced activation of the transient receptor potential A1 (TRPA1) channel, which has been reported to mediate neuropathic pain by sensing a variety of chemical irritants. Molecular docking and site-directed mutagenesis analyses suggested that saikosaponins bind to the hydrophobic pocket in TRPA1 near the Asn855 residue, which, when mutated to Ser, was previously associated with enhanced pain perception in humans. In support of these findings, saikosaponin D significantly attenuated agonist-induced nociceptive responses and vincristine-induced mechanical hypersensitivity in mice. These results indicate that saikosaponins are TRPA1 antagonists and provide a basis for further elaboration of saikosaponin derivatives for the development of new therapeutics for neuropathic pain.

Edgeworthia papyrifera Regulates Osteoblast and Osteoclast Differentiation In Vitro and Exhibits Anti-osteoporosis Activity in Animal Models of Osteoporosis.

Osteoporosis is a clinical condition characterized by low bone strength that leads to an increased risk of fracture. Strategies for the treatment of osteoporosis involve inhibition of bone resorption by osteoclasts and an increase of bone formation by osteoblasts. Here, we identified the extract derived from the stem part of Edgeworthia papyrifera that enhanced differentiation of MC3T3-E1 cells to osteoblast-like cells and inhibited osteoclast differentiation of RAW 264.7 cells in vitro. In support of our observation, rutin and daphnoretin, which were previously reported to inhibit osteoclast differentiation, were identified in E. papyrifera extract. In an animal model of osteoporosis, the ovariectomy-induced increases in bone resorption biomarkers such as pyridinoline and tartrate-resistant acid phosphatase were significantly reduced by E. papyrifera extract administration at 25.6 and 48.1%, respectively. Furthermore, the ovariectomy-induced bone loss in animal models of osteoporosis was significantly prevented by the administration of E. papyrifera in our study. Taking these observations into account, we suggest that E. papyrifera is an interesting candidate for further exploration as an anti-osteoporotic agent.

Salvia plebeia Extract Inhibits Xanthine Oxidase Activity In Vitro and Reduces Serum Uric Acid in an Animal Model of Hyperuricemia.

Hyperuricemia is a clinical condition characterized by an elevated level of serum uric acid and is a key risk factor for the development of gout and metabolic disorders. The existing urate-lowering therapies are often impractical for certain patient populations, providing a rationale to explore new agents with improved safety and efficacy. Here, we discovered that Salvia plebeia extract inhibited the enzyme activity of xanthine oxidase, which is a key enzyme generating uric acid in the liver. In an animal model of hyperuricemia, S. plebeia extract reduced serum urate to the levels observed in control animals. The urate-lowering effect of S. plebeia extract in vivo was supported by the identification of compounds that inhibit xanthine oxidase enzyme activity in vitro. Nepetin, scutellarein, and luteolin contributed significantly to S. plebeia bioactivity in vitro. These compounds showed the highest potency against xanthine oxidase with IC50 values of 2.35, 1.74, and 1.90 µM, respectively, and were present at moderate quantities. These observations serve as a basis for further elaboration of the S. plebeia extracts for the development of new therapeutics for hyperuricemia and related diseases.

Deciphering melanophagy: role of the PTK2-ITCH-MLANA-OPTN cascade on melanophagy in melanocytes.

Melanosomes play a pivotal role in skin color and photoprotection. In contrast to the well-elucidated pathway of melanosome biogenesis, the process of melanosome degradation, referred to as melanophagy, is largely unexplored. Previously, we discovered that 3,4,5-trimethoxycinnamate thymol ester (TCTE) effectively inhibits skin pigmentation by activating melanophagy. In this study, we discovered a new regulatory signaling cascade that controls melanophagy in TCTE-treated melanocytes. ITCH (itchy E3 ubiquitin protein ligase) facilitates ubiquitination of the melanosome membrane protein MLANA (melan-A) during TCTE-induced melanophagy. This ubiquitinated MLANA is then recognized by an autophagy receptor protein, OPTN (optineurin). Additionally, a phospho-kinase antibody array revealed that TCTE activates PTK2 (protein tyrosine kinase 2), which phosphorylates ITCH, enhancing the ubiquitination of MLANA. Furthermore, inhibition of either PTK2 or ITCH disrupts the ubiquitination of MLANA and the MLANA-OPTN interaction in TCTE-treated cells. Taken together, our findings highlight the critical role of the PTK2-ITCH-MLANA-OPTN cascade in orchestrating melanophagy progression.

Enhanced primary ciliogenesis via mitochondrial oxidative stress activates AKT to prevent neurotoxicity in HSPA9/mortalin-depleted SH-SY5Y cells.

The primary cilium, an antenna-like structure on the cell surface, acts as a mechanical and chemical sensory organelle. Primary cilia play critical roles in sensing the extracellular environment to coordinate various developmental and homeostatic signaling pathways. Here, we showed that the depletion of heat shock protein family A member 9 (HSPA9)/mortalin stimulates primary ciliogenesis in SH-SY5Y cells. The downregulation of HSPA9 enhances mitochondrial stress by increasing mitochondrial fragmentation and mitochondrial reactive oxygen species (mtROS) generation. Notably, the inhibition of either mtROS production or mitochondrial fission significantly suppressed the increase in primary ciliogenesis in HSPA9-depleted cells. In addition, enhanced primary ciliogenesis contributed to cell survival by activating AKT in SH-SY5Y cells. The abrogation of ciliogenesis through the depletion of IFT88 potentiated neurotoxicity in HSPA9-knockdown cells. Furthermore, both caspase-3 activation and cell death were increased by MK-2206, an AKT inhibitor, in HSPA9-depleted cells. Taken together, our results suggest that enhanced primary ciliogenesis plays an important role in preventing neurotoxicity caused by the loss of HSPA9 in SH-SY5Y cells.

Confirmation of Frm2 as a novel nitroreductase in Saccharomyces cerevisiae.

Nitroreductases comprise a group of FMN- or FAD-dependent enzymes that reduce nitrosubstituted compounds by using NAD(P)H, and are found in bacterial species and yeast. Although there is little information on the biological functions of nitroreductases, some studies suggest their possible involvement in oxidative stress responses. In the yeast Saccharomyces cerevisiae, a putative nitroreductase protein, Frm2, has been identified based on its sequence similarity with known bacterial nitroreductases. Frm2 has been reported to function in the lipid signaling pathway. To study the functions of Frm2, we measured the nitroreductase activity of purified Frm2 on 4-nitroquinoline-N-oxide (4-NQO) using NADH. LC-MS analysis of the reaction products revealed that Frm2 reduced NQO into 4-aminoquinoline-N-oxide (4-AQO) via 4-hydroxyaminoquinoline (4-HAQO). An Frm2 deletion mutant exhibited growth inhibition in the presence of 4-NQO. Thus, in this study, we demonstrate a novel nitroreductase activity of Frm2 and its involvement in the oxidative stress defense system.

Estrogen-like activity of aqueous extract from Agrimonia pilosa Ledeb. in MCF-7 cells.

BACKGROUND: Postmenopausal women experience estrogen deficiency-related menopausal symptoms (e.g., hot flashes and mood swings) and a dramatic increase in the incidence of chronic diseases. Although estrogen-replacement therapy (ERT) can reduce mortality from cardiovascular disease and improve osteoporosis and menopausal symptoms, its side effects have limited recent use. This study investigated the estrogen-like activity of aqueous extract from Agrimonia pilosa Ledeb. METHODS: The estrogenic activity of A. pilosa was investigated by using several in vitro assays. The binding activity of A. pilosa on estrogen receptors was examined using a fluorescence polarization-based competitive binding assay. The proliferative activity of A. pilosa was also examined using MCF-7 cells. Furthermore, the effect of A. pilosa on the expression of 3 estrogen-dependent genes was assessed. RESULTS: Using liquid chromatography-mass spectrometry, the 3 major peaks of A. pilosa aqueous extract were identified as apigenin-hexose, luteolin-glucuronide, and apigenin-glucuronide. The aqueous extract induced the proliferation of estrogen receptor-positive MCF-7 cells (p < 0.05). A. pilosa-stimulated proliferation was blocked on adding the estrogen antagonist ICI 182,780. Moreover, A. pilosa treatment increased the mRNA expression of the estrogen-responsive genes pS2 and PR (p < 0.05). CONCLUSIONS: These results suggest A. pilosa can be used to improve estrogen deficiency-related menopausal symptoms or to treat diseases in postmenopausal women.

Carnitine Protects against MPP+-Induced Neurotoxicity and Inflammation by Promoting Primary Ciliogenesis in SH-SY5Y Cells.

Primary cilia help to maintain cellular homeostasis by sensing conditions in the extracellular environment, including growth factors, nutrients, and hormones that are involved in various signaling pathways. Recently, we have shown that enhanced primary ciliogenesis in dopamine neurons promotes neuronal survival in a Parkinson's disease model. Moreover, we performed fecal metabolite screening in order to identify several candidates for improving primary ciliogenesis, including L-carnitine and acetyl-L-carnitine. However, the role of carnitine in primary ciliogenesis has remained unclear. In addition, the relationship between primary cilia and neurodegenerative diseases has remained unclear. In this study, we have evaluated the effects of carnitine on primary ciliogenesis in 1-methyl-4-phenylpyridinium ion (MPP+)-treated cells. We found that both L-carnitine and acetyl-L-carnitine promoted primary ciliogenesis in SH-SY5Y cells. In addition, the enhancement of ciliogenesis by carnitine suppressed MPP+-induced mitochondrial reactive oxygen species overproduction and mitochondrial fragmentation in SH-SY5Y cells. Moreover, carnitine inhibited the production of pro-inflammatory cytokines in MPP+-treated SH-SY5Y cells. Taken together, our findings suggest that enhanced ciliogenesis regulates MPP+-induced neurotoxicity and inflammation.

Nalfurafine Hydrochloride, a κ-Opioid Receptor Agonist, Induces Melanophagy via PKA Inhibition in B16F1 Cells.

Selective autophagy controls cellular homeostasis by degrading unnecessary or damaged cellular components. Melanosomes are specialized organelles that regulate the biogenesis, storage, and transport of melanin in melanocytes. However, the mechanisms underlying melanosomal autophagy, known as the melanophagy pathway, are poorly understood. To better understand the mechanism of melanophagy, we screened an endocrine-hormone chemical library and identified nalfurafine hydrochlorides, a κ-opioid receptor agonist, as a potent inducer of melanophagy. Treatment with nalfurafine hydrochloride increased autophagy and reduced melanin content in alpha-melanocyte-stimulating hormone (α-MSH)-treated cells. Furthermore, inhibition of autophagy blocked melanosomal degradation and reversed the nalfurafine hydrochloride-induced decrease in melanin content in α-MSH-treated cells. Consistently, treatment with other κ-opioid receptor agonists, such as MCOPPB or mianserin, inhibited excessive melanin production but induced autophagy in B16F1 cells. Furthermore, nalfurafine hydrochloride inhibited protein kinase A (PKA) activation, which was notably restored by forskolin, a PKA activator. Additionally, forskolin treatment further suppressed melanosomal degradation as well as the anti-pigmentation activity of nalfurafine hydrochloride in α-MSH-treated cells. Collectively, our data suggest that stimulation of κ-opioid receptors induces melanophagy by inhibiting PKA activation in α-MSH-treated B16F1 cells.

Effects of a Pre-Exercise Meal on Plasma Growth Hormone Response and Fat Oxidation during Walking.

The purpose of this study was to determine the effects of a pre-exercise meal on the plasma human growth hormone (hGH) response and fat oxidation during walking. Subjects (n=8) were randomly provided with either 1 g/kg body weight of glucose in 200 mL water (CHO) or 200 mL water alone (CON) 30 min prior to exercise and subsequently walked on a treadmill at 50% of VO2max for 60 min. Plasma hGH concentrations were significantly higher in subjects who received CHO compared to those who received CON at 15 and 30 min. The fat oxidation rate in the CHO was significantly lower than the CON while walking for 5~15, 25~35 and 45~55 min. Plasma FFA levels were also significantly lower in the CHO compared to the CON at 30, 45 and 60 min. Plasma glucose levels in the CHO were significantly lower while plasma insulin levels were significantly higher than in the CON at 15 and 30 min. Therefore, the results of this study suggest that the elevation of plasma hGH levels due to the intake of a pre-exercise meal may not be strongly related to fat oxidation and plasma free fatty acid (FFA) levels during low-intensity exercise.

Generation of demyelination models by targeted ablation of oligodendrocytes in the zebrafish CNS.

Demyelination is the pathological process by which myelin sheaths are lost from around axons, and is usually caused by a direct insult targeted at the oligodendrocytes in the vertebrate central nervous system (CNS). A demyelinated CNS is usually remyelinated by a population of oligodendrocyte progenitor cells, which are widely distributed throughout the adult CNS. However, myelin disruption and remyelination failure affect the normal function of the nervous system, causing human diseases such as multiple sclerosis. In spite of numerous studies aimed at understanding the remyelination process, many questions still remain unanswered. Therefore, to study remyelination mechanisms in vivo, a demyelination animal model was generated using a transgenic zebrafish system in which oligodendrocytes are conditionally ablated in the larval and adult CNS. In this transgenic system, bacterial nitroreductase enzyme (NTR), which converts the prodrug metronidazole (Mtz) into a cytotoxic DNA cross-linking agent, is expressed in oligodendrocyte lineage cells under the control of the mbp and sox10 promoter. Exposure of transgenic zebrafish to Mtz-containing media resulted in rapid ablation of oligodendrocytes and CNS demyelination within 48 h, but removal of Mtz medium led to efficient remyelination of the demyelinated CNS within 7 days. In addition, the demyelination and remyelination processes could be easily observed in living transgenic zebrafish by detecting the fluorescent protein, mCherry, indicating that this transgenic system can be used as a valuable animal model to study the remyelination process in vivo, and to conduct high-throughput primary screens for new drugs that facilitate remyelination.