Role of recA/RAD51 family proteins in mammals.

DNA damage causes chromosomal instability leading to oncogenesis, apoptosis, and severe failure of cell functions. The DNA repair system includes base excision repair, nucleotide excision repair, mismatch repair, translesion replication, non-homologous end-joining, and recombinational repair. Homologous recombination performs the recombinational repair. The RAD51 gene is an ortholog of Esherichia coli recA, and the gene product Rad51 protein plays a central role in the homologous recombination. In mammals, 7 recA-like genes have been identified: RAD51, RAD51L1/B, RAD51L2/C, RAD51L3/D, XRCC2, XRCC3, and DMC1. These genes, with the exception of meiosis-specific DMC1, are essential for development in mammals. Disruption of the RAD51 gene leads to cell death, whereas RAD51L1/B, RAD51L2/C, RAD51L3/D, XRCC2, and XRCC3 genes (RAD51 paralogs) are not essential for viability of cells, but these gene-deficient cells exhibit a similar defective phenotype. Yeast two-hybrid analysis, co-immunoprecipitation, mutation analysis, and domain mapping of Rad51 and Rad51 paralogs have revealed protein-protein interactions among these gene products. Recent investigations have shown that Rad51 paralogs play a role not only in an early step, but also in a late step of homologous recombination. In addition, identification of alternative transcripts of some RAD51 paralogs may reflect the complexity of the homologous recombination system.</p

Multiple Roles of Histidine-Rich Glycoprotein in Vascular Homeostasis and Angiogenesis

Histidine-rich glycoprotein (HRG) is a 75 kDa plasma protein that is synthesized in the liver of many verte-brates and present in their plasma at relatively high concentrations of 100-150 μg/mL. HRG is an abundant and well-characterized protein having a multidomain structure that enable it to interact with many ligands, func-tion as an adaptor molecule, and participate in numerous physiological and pathological processes. As a plasma protein, HRG has been reported to regulate vascular biology, including coagulation, fibrinolysis and angiogenesis, through its binding with several ligands (heparin, FXII, fibrinogen, thrombospondin, and plas-minogen) and interaction with many types of cells (endothelial cells, erythrocytes, neutrophils and platelets). This review aims to summarize the roles of HRG in maintaining vascular homeostasis and regulating angiogen-esis in various pathological conditions

Usefulness of High Mobility Group Box 1 Protein as a Plasma Biomarker in Patient with Peripheral Artery Disease

Atherosclerosis is often associated with chronic vascular inflammation. High-mobility group box 1 protein (HMGB1) plays various roles, not only as a transcriptional regulatory factor in the nucleus, but also as an inflammatory mediator. A previous study suggested that fibrinogen is an important factor associated with atherosclerosis progression. The present study was performed to examine the levels of plasma HMGB1 protein in atherosclerosis patients. We studied 24 patients with peripheral artery disease (PAD) with atherosclerosis, and 10 healthy controls. We found that the concentrations of HMGB1 were increased in the plasma of the patients with atherosclerosis, and there were significant correlations between the plasma HMGB1 and fibrinogen levels. Plasma HMGB1 may play a key role in the pathogenesis of clinical and experimental atherosclerosis

High Mobility Group Box-1 and Blood-Brain Barrier Disruption

Increasing evidence suggests that inflammatory responses are involved in the progression of brain injuries induced by a diverse range of insults, including ischemia, hemorrhage, trauma, epilepsy, and degenerative diseases. During the processes of inflammation, disruption of the blood–brain barrier (BBB) may play a critical role in the enhancement of inflammatory responses and may initiate brain damage because the BBB constitutes an interface between the brain parenchyma and the bloodstream containing blood cells and plasma. The BBB has a distinct structure compared with those in peripheral tissues: it is composed of vascular endothelial cells with tight junctions, numerous pericytes surrounding endothelial cells, astrocytic endfeet, and a basement membrane structure. Under physiological conditions, the BBB should function as an important element in the neurovascular unit (NVU). High mobility group box-1 (HMGB1), a nonhistone nuclear protein, is ubiquitously expressed in almost all kinds of cells. HMGB1 plays important roles in the maintenance of chromatin structure, the regulation of transcription activity, and DNA repair in nuclei. On the other hand, HMGB1 is considered to be a representative damage-associated molecular pattern (DAMP) because it is translocated and released extracellularly from different types of brain cells, including neurons and glia, contributing to the pathophysiology of many diseases in the central nervous system (CNS). The regulation of HMGB1 release or the neutralization of extracellular HMGB1 produces beneficial effects on brain injuries induced by ischemia, hemorrhage, trauma, epilepsy, and Alzheimer’s amyloidpathy in animal models and is associated with improvement of the neurological symptoms. In the present review, we focus on the dynamics of HMGB1 translocation in different disease conditions in the CNS and discuss the functional roles of extracellular HMGB1 in BBB disruption and brain inflammation. There might be common as well as distinct inflammatory processes for each CNS disease. This review will provide novel insights toward an improved understanding of a common pathophysiological process of CNS diseases, namely, BBB disruption mediated by HMGB1. It is proposed that HMGB1 might be an excellent target for the treatment of CNS diseases with BBB disruption

The Role of High Mobility Group Box-1 in Epileptogenesis

High mobility group box-1 (HMGB1) is a non-histone, DNA-binding nuclear protein belonging to the family of damage-associated molecular patterns (DAMPs). HMGB1 has been reported to play an important role during epileptogenesis although the mechanisms of its actions are still not clear. Many hypotheses have been suggested especially about the relationship between HMGB1 and inflammation responses and blood-brain barrier disruption during epileptogenesis. In this review, we will mainly discuss the role of HMGB1 in epileptogenesis

High mobility group box 1 complexed with heparin induced angiogenesis in a matrigel plug assay

Angiogenesis involves complex processes mediated by several factors and is associated with inflammation and wound healing. High mobility group box 1 (HMGB1) is released from necrotic cells as well as macrophages and plays proinflammatory roles. In the present study, we examined whether HMGB1 would exhibit angiogenic activity in a matrigel plug assay in mice. HMGB1 in combination with heparin strongly induced angiogenesis, whereas neither HMGB1 nor heparin alone showed such angiogenic activity. The heparin-dependent induction of angiogenesis by HMGB1 was accompanied by increases in the expression of tumor necrosis factor-alpha (TNF-alpha) and vascular endothelial growth factor-A120 (VEGF-A120). It is likely that the dependence of the angiogenic activity of HMGB1 on heparin was due to the efficiency of the diffusion of the HMGB1-heparin complex from matrigel to the surrounding areas. VEGF-A165 possessing a heparin-binding domain showed a pattern of heparin-dependent angiogenic activity similar to that of HMGB1. The presence of heparin also inhibited the degradation of HMGB1 by plasmin in vitro. Taken together, these results suggested that HMGB1 in complex with heparin possesses remarkable angiogenic activity, probably through the induction of TNF-alpha and VEGF-A120.</p

The inhibition of substance P-induced histamine release from mast cells by 6, 7-dihydro-6, 8, 8, 10-tetramethyl-8H-pyrano-[3, 2-g] chromone-2-carboxylic acid (EAA).

In the presence of extracellular Ca2+, 6,7-dihydro-6,8,8, 10-tetramethyl-8H-pyrano [3, 2-g] chromone-2-carboxylic acid (EAA) had an inhibitory effect on the substance P-induced histamine release from rat peritoneal mast cells. Not only Ca2+ but also Mg2+, Sr2+ and Ba2+ were effective in enhancing the activity of EAA. Marked tachyphylaxis to EAA developed irrespective of the presence or absence of extracellular Ca2+. Cross-tachyphylaxis was observed between EAA and disodium cromoglycate (DSCG). These results indicate that the mode of action of EAA is similar, but not identical, with that of DSCG.</p

For Vol.68, No.3 pp157-162 Usefulness of High Mobility Group Box 1 Protein as a Plasma Biomarker in Patient with Peripheral Artery Disease

Atherosclerosis is often associated with chronic vascular inflammation. High-mobility group box 1 protein (HMGB1) plays various roles, not only as a transcriptional regulatory factor in the nucleus, but also as an inflammatory mediator. A previous study suggested that fibrinogen is an important factor associated with atherosclerosis progression. The present study was performed to examine the levels of plasma HMGB1 protein in atherosclerosis patients. We studied 24 patients with peripheral artery disease (PAD) with atherosclerosis, and 10 healthy controls. We found that the concentrations of HMGB1 were increased in the plasma of the patients with atherosclerosis, and there were significant correlations between the plasma HMGB1 and fibrinogen levels. Plasma HMGB1 may play a key role in the pathogenesis of clinical and experimental atherosclerosis

Phencyclidine and the Dynamics of Mouse Brain Histamine

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