A myeloid leukemia factor homolog involved in encystation-induced protein metabolism in Giardia lamblia.

BACKGROUND: Giardia lamblia differentiates into resistant cysts as an established model for dormancy. Myeloid leukemia factor (MLF) proteins are important regulators of cell differentiation. Giardia possesses a MLF homolog which was up-regulated during encystation and localized to unknown cytosolic vesicles named MLF vesicles (MLFVs). METHODS: We used double staining for visualization of potential factors with role in protein metabolism pathway and a strategy that employed a deletion mutant, CDK2m3, to test the protein degradation pathway. We also explored whether autophagy or proteasomal degradation are regulators of Giardia encystation by treatment with MG132, rapamycin, or chloroquine. RESULTS: Double staining of MLF and ISCU or CWP1 revealed no overlap between their vesicles. The aberrant CDK2m3 colocalized with MLFVs and formed complexes with MLF. MG132 increased the number of CDK2m3-localized vesicles and its protein level. We further found that MLF colocalized and interacted with a FYVE protein and an ATG8-like (ATG8L) protein, which were up-regulated during encystation and their expression induced Giardia encystation. The addition of MG132, rapamycin, or chloroquine, increased their levels and the number of their vesicles, and inhibited the cyst formation. MLF and FYVE were detected in exosomes released from culture. CONCLUSIONS: The MLFVs are not mitosomes or encystation-specific vesicles, but are related with degradative pathway for CDK2m3. MLF, FYVE, and ATG8L play a positive role in encystation and function in protein clearance pathway, which is important for encystation and coordinated with Exosomes. GENERAL SIGNIFICANCE: MLF, FYVE, and ATG8L may be involved an encystation-induced protein metabolism during Giardia differentiation.

The therapeutic effect of aucubin-supplemented hyaluronic acid on interleukin-1beta-stimulated human articular chondrocytes.

BACKGROUND: Injection of exogenous hyaluronic acid (HA) into the joint capsule improves symptoms of early stage osteoarthritis (OA). However, reactive oxygen species degrade HA into small oligosaccharides that can elicit pro-inflammatory responses. Likewise, disturbance of the antioxidant enzyme system and generation of oxidative stress by pro-inflammatory cytokines worsen knee OA. Accordingly, we proposed the use of aucubin, an antioxidant and anti-inflammatory compound, as a versatile adjuvant to HA for treating OA. METHODS: Primary human chondrocytes were cultured in media supplemented with aucubin in a series of concentrations (0, 0.01, 0.1, 1, and 10 µg/ml) to study dose-dependent toxicity. We then evaluated the therapeutic effects of HA (100 µg/ml) supplemented with aucubin (10 µg/ml) on interleukin-1 beta (IL-1ß, 10 ng/ml)-stimulated chondrocytes. RESULTS: The use of aucubin did not change cell viability or alter lactate dehydrogenase release to normal chondrocytes. Although the proliferation and sulfated glycosaminoglycan production were not affected, aucubin partially restored the hypertrophic transformation of chondrocytes. Relative to treatment with HA or aucubin alone, real-time PCR revealed that aucubin-supplemented HA down-regulated the mRNA levels of tumor necrosis factor-alpha (TNF-α), corrected collagen type 1 and aggrecan, and up-regulated tissue inhibitor of metalloproteinase 1. Moreover, ELISA testing also showed a reduced TNF-α production. Although superoxide dismutases activity was still distributed, aucubin restored total antioxidant capacity of IL-1ß-stimulated chondrocytes. Western blotting further showed that aucubin inhibited cyclooxygenase-2 and regulated the nuclear factor (erythroid-derived 2)-like 2 pathway. CONCLUSION: Aucubin can enhance the anti-catabolic and anti-inflammatory effects of HA on OA chondrocytes.

Synergistic effect of l-ascorbic acid and hyaluronic acid on the expressions of matrix metalloproteinase-3 and -9 in human chondrocytes.

Proinflammatory cytokines and reactive oxygen species (ROS) are known to be involved in the initiation and progression of osteoarthritis (OA). New evidence clarifying the correlation between ROS and inflammation has indicated that oxidative stress can up-regulate inflammatory cytokines. l-Ascorbic acid (AA), an antioxidant, has been shown to have anti-inflammatory effects and improve matrix deposition in chondrocytes. The purpose of this study was to examine the effects of hyaluronic acid (HA; 100 µg/mL) supplemented with AA (50 µg/mL) on human normal and interleukin-1 beta-stimulated (IL-1ß, 10 ng/mL) chondrocytes. HA, AA, and HA + AA treatment did not change cell morphology, viability, proliferation, and glycosaminoglycan production in normal chondrocytes. HA, AA, and HA + AA, by contrast, partially restored viability and morphology of hypertrophic chondrocytes, and HA and HA + AA further decreased the cytotoxicity of IL-1ß. Real-time PCR revealed that AA and HA + AA had no substantial effects on unstimulated chondrocytes, except for down-regulation of matrix metalloproteinase (MMP)-9 mRNA levels. For IL-1ß-stimulated chondrocytes, significant down-regulation of IL-1ß, tumor necrosis factor-alpha (TNF-α), MMP-3, and MMP-9 mRNA expression was found when cells were cultured in HA-supplemented media. Moreover, HA + AA supplementation further significantly decreased MMP-3 and MMP-9 mRNA expression. The protein production of MMP-3 was decreased, with a significant difference between the HA + AA group and HA group. The antioxidant capacity and superoxide dismutases activity were also partially restored in stimulated chondrocytes. HA supplemented with AA modulates MMPs expression and antioxidant fuction in chondrocytes. AA may enhance the anticatabolic effects of HA on OA chondrocytes. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1809-1817, 2018.