Mitophagy stimulation as a novel strategy for the treatment of mitochondrial diseases

Mitophagy, the selective degradation of damaged or surplus mitochondria using core autophagy machinery, plays an essential role in maintaining cellular mitochondrial function. Impaired mitophagy is closely linked to various human diseases, including neurodegenerative diseases, cardiovascular diseases, cancers and kidney disease. Defective mitophagy induces the accumulation of damaged mitochondria and thereby results in a decline in cellular survival and tissue function. Accordingly, enhancement of mitophagy has been proposed as a novel strategy for the treatment of human diseases closely linked to mitochondrial dysfunction. Recent studies showing that the stimulation of mitophagy has a therapeutic effect on several disease models highlight the possibility of disease treatment using mitophagy. The development of mitophagy inducers with toxicity and the identification of molecular mechanisms will enable the clinical application of mitophagy-based treatments.

Spinosin Attenuates Alzheimer’s Disease-Associated Synaptic Dysfunction via Regulation of Plasmin Activity

Hippocampal synaptic dysfunction is a hallmark of Alzheimer’s disease (AD). Many agents regulating hippocampal synaptic plasticity show an ameliorative effect on AD pathology, making them potential candidates for AD therapy. In the present study, we investigated spinosin as a regulating agent of synaptic plasticity in AD. Spinosin attenuated amyloid β (Aβ)-induced long-term potentiation (LTP) impairment, and improved plasmin activity and protein level in the hippocampi of 5XFAD mice, a transgenic AD mouse model. Moreover, the effect of spinosin on hippocampal LTP in 5XFAD mice was prevented by 6-aminocaproic acid, a plasmin inhibitor. These results suggest that spinosin improves synaptic function in the AD hippocampus by regulating plasmin activity.

Clinical Significance of Peroxisome Proliferator-Activated Receptor gamma and TRAP220 in Patients with Operable Colorectal Cancer / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: The peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor that regulates expression of mediators of lipid metabolism and the inflammatory response. Thyroid hormone receptor-associated proteins 220 (TRAP220) is an essential component of the TRAP/Mediator complex. The objective of this study was to clarify whether PPARgamma or TRAP220 are significant prognostic markers in resectable colorectal cancer (CRC). MATERIALS AND METHODS: A total of 399 patients who underwent curative resection for CRC were enrolled. We investigated the presence of PPARgamma and TARP220 in CRC tissues and adjacent normal tissues by immunohistochemistry. Correlation between the expression of these factors and clinicopathologic features and survival was investigated. RESULTS: Median age of the patients was 63 years (range, 22 to 87 years), and median follow-up duration 61.1 months (range, 2 to 114 months). PPARgamma and TRAP220 expression showed significant correlation with depth of invasion (p=0.013 and p=0.001, respectively). Expression of TRAP220 also showed association with lymph node metastasis and TNM stage (p=0.001). Compared with patients with TRAP220 negative tumors, patients with TRAP220 positive tumors had longer 5-year disease-free survival (DFS) tendency (p=0.051). Patients who were PPARgamma positive combined with TRAP220 positive had a better 5-year DFS (64.8% vs. 79.3%, p=0.013). In multivariate analysis expression of both PPARgamma and TRAP220 significantly affected DFS (hazard ratio, 0.620; 95% confidence interval, 0.379 to 0.997; p=0.048). CONCLUSION: TRAP220 may be a valuable marker for nodal metastasis and TNM stage. Tumor co-expression of PPARgamma and TRAP220 represents a biomarker for good prognosis in CRC patients.

A pertussis toxin sensitive G-protein-independent pathway is involved in serum amyloid A-induced formyl peptide receptor 2-mediated CCL2 production

Serum amyloid A (SAA) induced CCL2 production via a pertussis toxin (PTX)-insensitive pathway in human umbilical vein endothelial cells (HUVECs). SAA induced the activation of three MAPKs (ERK, p38 MAPK, and JNK), which were completely inhibited by knock-down of formyl peptide receptor 2 (FPR2). Inhibition of p38 MAPK and JNK by their specific inhibitors (SB203580 and SP600125), or inhibition by a dominant negative mutant of p38 MAPK dramatically decreased SAA-induced CCL2 production. Inactivation of Gi protein(s) by PTX inhibited the activation of SAA-induced ERK, but not p38 MAPK or JNK. The results indicate that SAA stimulates FPR2-mediated activation of p38 MAPK and JNK, which are independent of a PTX-sensitive G-protein and are essential for SAA-induced CCL2 production.

Lysophosphatidylglycerol inhibits formyl peptide receptor like-1-stimulated chemotactic migration and IL-1beta production from human phagocytes

In this study, we observed that lysophosphatidylglycerol (LPG) completely inhibited a formyl peptide receptor like-1 (FPRL1) agonist (MMK-1)-stimulated chemotactic migration in human phagocytes, such as neutrophils and monocytes. LPG also dramatically inhibited IL-1beta production by another FPRL1 agonist serum amyloid A (SAA) in human phagocytes. However, LPG itself induced intracellular calcium increase and superoxide anion production in human phagocytes. Keeping in mind that phagocytes migration and IL-1beta production by FPRL1 are important for the induction of inflammatory response, our data suggest that LPG can be regarded as a useful material for the modulation of inflammatory response induced by FPRL1 activation.

LL-37 inhibits serum amyloid A-induced IL-8 production in human neutrophils

Serum amyloid A (SAA) has been regarded as an important mediator of inflammatory responses. The effect of several formyl peptide receptor-like 1 (FPRL1) ligands on the production of IL-8 by SAA was investigated in human neutrophils. Among the ligands tested, LL-37 was found to specifically inhibit SAA-induced IL-8 production in transcriptional and post-transcriptional levels. Since SAA stimulated IL-8 production via ERK and p38 MAPK in human neutrophils, we tested the effect of LL-37 on SAA induction for these two MAPKs. LL-37 caused a dramatic inhibition of ERK and p38 MAPK activity, which is induced by SAA. LL-37 was also found to inhibit SAA-stimulated neutrophil chemotactic migration. Further, the LL-37-induced inhibitory effect was mediated by FPRL1. Our findings indicate that LL-37 is expected to be useful in the inhibition of SAA signaling and for the development of drugs against SAA-related inflammatory diseases.

LL-37 inhibits serum amyloid A-induced IL-8 production in human neutrophils

Serum amyloid A (SAA) has been regarded as an important mediator of inflammatory responses. The effect of several formyl peptide receptor-like 1 (FPRL1) ligands on the production of IL-8 by SAA was investigated in human neutrophils. Among the ligands tested, LL-37 was found to specifically inhibit SAA-induced IL-8 production in transcriptional and post-transcriptional levels. Since SAA stimulated IL-8 production via ERK and p38 MAPK in human neutrophils, we tested the effect of LL-37 on SAA induction for these two MAPKs. LL-37 caused a dramatic inhibition of ERK and p38 MAPK activity, which is induced by SAA. LL-37 was also found to inhibit SAA-stimulated neutrophil chemotactic migration. Further, the LL-37-induced inhibitory effect was mediated by FPRL1. Our findings indicate that LL-37 is expected to be useful in the inhibition of SAA signaling and for the development of drugs against SAA-related inflammatory diseases.

Phytosphingosine-1-phosphate stimulates chemotactic migration of L2071 mouse fibroblasts via pertussis toxin-sensitive G-proteins

Phytosphingosine-1-phosphate (PhS1P) was found to stimulate an intracellular calcium increase via phospholipase C but not pertussis toxin (PTX)- sensitive G-proteins in L2071 mouse fibroblasts. PhS1P also activated ERK and p38 kinase, and these activations by PhS1P were inhibited by PTX. Moreover, PhS1P stimulated the chemotactic migration of L2071 cells via PTX-sensitive Gi protein(s). In addition, the PhS1P-induced chemotactic migration of L2071 cells was also dramatically inhibited by LY294002 and SB203580 (inhibitors of phosphoinositide 3-kinase and p38 kinase, respectively). L2071 cells are known to express four S1P receptors, i.e., S1P1, S1P2, S1P3, and S1P4, and pretreatment with an S1P1 and S1P3 antagonist (VPC 23019) did not affect on PhS1P-induced chemotaxis. This study demonstrates that PhS1P stimulates at least two different signaling cascades, one is a PTX-insensitive but phospholipase C dependent intracellular calcium increase, and the other is a PTX-sensitive chemotactic migration mediated by phosphoinositide 3-kinase and p38 kinase.

Identification of novel substrates for human checkpoint kinase Chk1 and Chk2 through genome-wide screening using a consensus Chk phosphorylation motif

Checkpoint kinase 1 (Chk1) and Chk2 are effector kinases in the cellular DNA damage response and impairment of their function is closely related to tumorigenesis. Previous studies revealed several substrate proteins of Chk1 and Chk2, but identification of additional targets is still important in order to understand their tumor suppressor functions. In this study, we screened novel substrates for Chk1 and Chk2 using substrate target motifs determined previously by an oriented peptide library approach. The potential candidates were selected by genome-wide peptide database searches and were examined by in vitro kinase assays. ST5, HDAC5, PGC-1alpha, PP2A PR130, FANCG, GATA3, cyclin G, Rad51D and MAD1alpha were newly identified as in vitro substrates for Chk1 and/or Chk2. Among these, HDAC5 and PGC-1alpha were further analyzed to substantiate the screening results. Immunoprecipitation kinase assay of full-length proteins and site-directed mutagenesis analysis of the target motifs demonstrated that HDAC5 and PGC-1alpha were specific targets for Chk1 and/or Chk2 at least in vitro.

Transcription repression of a CCAAT-binding transcription factor CBF/HSP70 by p53

NF-Y transcription factor binds to CCAAT boxes on promoters of cell cycle regulatory genes such as cdc2, cyclin B, cdc25C, and cyclin A. We previously reported that the DNA binding activity of NF-Y is regulated by p53-p21-cdk2 pathway. CBF/HSP70 was originally identified as a transcription factor binding to the CCAAT box on the hsp70 promoter and mediates transcription repression of hsp70 pro- moter by p53. Recently it was demonstrated that CBF/HSP70 interacts and cooperates with NF-Y. In this study, we found that p53 represses the transcription of CBF/HSP70. Since transactivation ability of NF-Y is regulated in a cell cycle-dependent manner, we examined the transcription of CBF/HSP70 during the cell cycle. After synchronization of a human bladder carcinoma cell lacking functional p53 at early S phase, we infect the cells with adenovirus encoding p53. Cells infected with control virus progressed to S and G2 after release from the arrest. In contrast, cells expressing p53 enter S and G2 phases, but arrest at G2/M. The expression of CBF/HSP70 was induced at S/G2 phase in cells infected with a control virus, but kept to be repressed in cells expressing p53. Thus, these results suggest that p53 suppresses the expression of cell cycle regulatory genes though inhibiting both CCAAT binding factors, CBF/HSP70 and NF-Y.