LOX-1 inhibition in myocardial ischemia-reperfusion injury: modulation of MMP-1 and inflammation

A recently identified lectin-like oxidized low-density lipoprotein receptor (LOX-1) mediates endothelial cell injury and facilitates inflammatory cell adhesion. We studied the role of LOX-1 in myocardial ischemia-reperfusion (I/R) injury. Anesthetized Sprague-Dawley rats were subjected to 60 min of left coronary artery (LCA) ligation, followed by 60 min of reperfusion. Rats were treated with saline, LOX-1 blocking antibody JXT21 (10 mg/kg), or nonspecific anti-goat IgG (10 mg/kg) before I/R. Ten other rats underwent surgery without LCA ligation and served as a sham control group. LOX-1 expression was markedly increased during I/R (P < 0.01 vs. sham control group). Simultaneously, the expression of matrix metalloproteinase-1 (MMP-1) and adhesion molecules (P-selectin, VCAM-1, and ICAM-1) was also increased in the I/R area (P < 0.01 vs. sham control group). There was intense leukocyte accumulation in the I/R area in the saline-treated group. Treatment of rats with the LOX-1 antibody prevented I/R-induced upregulation of LOX-1 and reduced MMP-1 and adhesion molecule expression as well as leukocyte recruitment. LOX-1 antibody, but not nonspecific IgG, also reduced myocardial infarct size (P < 0.01 vs. saline-treated I/R group). To explore the link between LOX-1 and adhesion molecule expression, we measured expression of oxidative stress-sensitive p38 mitogen-activated protein kinase (p38 MAPK). The activity of p38 MAPK was increased during I/R (P < 0.01 vs. sham control), and use of LOX-1 antibody inhibited p38 MAPK activation (P < 0.01). These findings indicate that myocardial I/R upregulates LOX-1 expression, which through p38 MAPK activation increases the expression of MMP-1 and adhesion molecules. Inhibition of LOX-1 exerts an important protective effect against myocardial I/R injury.     

Alzheimer's disease-related overexpression of the cation-dependent mannose 6-phosphate receptor increases Abeta secretion: role for altered lysosomal hydrolase distribution in beta-amyloidogenesis

Prominent endosomal and lysosomal changes are an invariant feature of neurons in sporadic Alzheimer's disease (AD). These changes include increased levels of lysosomal hydrolases in early endosomes and increased expression of the cation-dependent mannose 6-phosphate receptor (CD-MPR), which is partially localized to early endosomes. To determine whether AD-associated redistribution of lysosomal hydrolases resulting from changes in CD-MPR expression affects amyloid precursor protein (APP) processing, we stably transfected APP-overexpressing murine L cells with human CD-MPR. As controls for these cells, we also expressed CD-MPR trafficking mutants that either localize to the plasma membrane (CD-MPRpm) or to early endosomes (CD-MPRendo). Expression of CD-MPR resulted in a partial redistribution of a representative lysosomal hydrolase, cathepsin D, to early endosomal compartments. Turnover of APP and secretion of sAPPalpha and sAPPbeta were not altered by overexpression of any of the CD-MPR constructs. However, secretion of both human Abeta40 and Abeta42 into the growth media nearly tripled in CD-MPR- and CD-MPRendo-expressing cells when compared with parental or CD-MPRpm-expressing cells. Comparable increases were confirmed for endogenous mouse Abeta40 in L cells expressing these CD-MPR constructs but not overexpressing human APP. These data suggest that redistribution of lysosomal hydrolases to early endocytic compartments mediated by increased expression of the CD-MPR may represent a potentially pathogenic mechanism for accelerating Abeta generation in sporadic AD, where the mechanism of amyloidogenesis is unknown.     

Matrix-assisted laser desorption ionization--time of flight mass spectrometry of lipopeptide biosurfactants in whole cells and culture filtrates of Bacillus subtilis C-1 isolated from petroleum sludge

An innovative method was developed for rapid sensitive detection and efficient structural characterization of lipopeptide biosurfactants by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry by using whole microbial cells and crude culture filtrates as targets in combination with surface tension measurements. This was done for a bacterial strain that was isolated from petroleum sludge and efficiently produces biosurfactants. This organism was identified by using biochemical, physiological, and genetic parameters as a Bacillus subtilis strain, designated B. subtilis C-1. This assignment was supported by a mass spectrometric investigation of the secondary metabolite spectrum determined by whole-cell MALDI-TOF mass spectrometry, which revealed three lipopeptide complexes, the surfactins, the iturins, and the fengycins, which are well-known biosurfactants produced by B. subtilis strains. These compounds were structurally characterized by in situ structure analysis by using postsource decay MALDI-TOF mass spectrometry. The isoforms were separated by miniaturized high-resolution reversed-phase high-performance liquid chromatography for mass spectrometric characterization. Iturin compounds which contain unusual fatty acid components were detected.     

IFN-gamma-inducible protein 10 (CXCL10) contributes to airway hyperreactivity and airway inflammation in a mouse model of asthma

Allergic asthma is an inflammatory disease of the airways characterized by eosinophilic inflammation and airway hyper-reactivity. Cytokines and chemokines specific for Th2-type inflammation predominate in asthma and in animal models of this disease. The role of Th1-type inflammatory mediators in asthma remains controversial. IFN-gamma-inducible protein 10 (IP-10; CXCL10) is an IFN-gamma-inducible chemokine that preferentially attracts activated Th1 lymphocytes. IP-10 is up-regulated in the airways of asthmatics, but its function in asthma is unclear. To investigate the role of IP-10 in allergic airway disease, we examined the expression of IP-10 in a murine model of asthma and the effects of overexpression and deletion of IP-10 in this model using IP-10-transgenic and IP-10-deficient mice. Our experiments demonstrate that IP-10 is up-regulated in the lung after allergen challenge. Mice that overexpress IP-10 in the lung exhibited significantly increased airway hyperreactivity, eosinophilia, IL-4 levels, and CD8(+) lymphocyte recruitment compared with wild-type controls. In addition, there was an increase in the percentage of IL-4-secreting T lymphocytes in the lungs of IP-10-transgenic mice. In contrast, mice deficient in IP-10 demonstrated the opposite results compared with wild-type controls, with a significant reduction in these measures of Th2-type allergic airway inflammation. Our results demonstrate that IP-10, a Th1-type chemokine, is up-regulated in allergic pulmonary inflammation and that this contributes to the airway hyperreactivity and Th2-type inflammation seen in this model of asthma.     

Cutting edge: Th2 cell trafficking into the allergic lung is dependent on chemoattractant receptor signaling

Th2 cells are recruited to the lung where they mediate the asthma phenotype. Since the molecular mechanisms regulating Th2 cell trafficking remain unknown, we sought to determine whether trafficking of Th2 cells into the lung is mediated by G alpha i-coupled chemoattractant receptors. We show here that in contrast to untreated Th2 cells, pertussis toxin-treated Th2 cells were unable to traffic into the lung, airways, or lymph nodes following Ag challenge and therefore were unable to induce allergic inflammation in vivo. Pertussis toxin-treated Th2 cells were functional cells, however, and when directly instilled into the airways of mice, bypassing their need to traffic to the lung, were able to induce airway eosinophilic inflammation. These studies conclusively demonstrate that trafficking of Th2 cells into the lung is an active process dependent on chemoattractant receptors.     

Identification of domains in apobec-1 complementation factor required for RNA binding and apolipoprotein-B mRNA editing

The C-to-U editing of apolipoprotein-B (apo-B) mRNA is catalyzed by an enzyme complex that recognizes an 11-nt mooring sequence downstream of the editing site. A minimal holoenzyme that edits apo-B mRNA in vitro has been defined. This complex contains apobec-1, the catalytic subunit, and apobec-1 complementation factor (ACF), the RNA-binding subunit that binds to the mooring sequence. Here, we show that ACF binds with high affinity to single-stranded but not double-stranded apo-B mRNA. ACF contains three nonidentical RNA recognition motifs (RRM) and a unique C-terminal auxiliary domain. In many multi-RRM proteins, the RRMs mediate RNA binding and an auxiliary domain functions in protein-protein interactions. Here we show that ACF does not fit this simple model. Based on deletion mutagenesis, the RRMs in ACF are necessary but not sufficient for binding to apo-B mRNA. Amino acids in the pre-RRM region are required for complementing activity and RNA binding, but not for interaction with apobec-1. The C-terminal 196 amino acids are not absolutely essential for function. However, further deletion of an RG-rich region from the auxiliary domain abolished complementing activity, RNA binding, and apobec-1 interaction. The auxiliary domain alone did not bind apobec-1. Although all three RRMs are required for complementing activity and apobec-1 interaction, the individual motifs contribute differently to RNA binding. Point mutations in RRM1 or RRM2 decreased the Kd for apo-B mRNA by two orders of magnitude whereas mutations in RRM3 reduced binding affinity 13-fold. The pairwise expression of RRM1 with RRM2 or RRM3 resulted in moderate affinity binding.     

Studies of apoptosis and bcl-2 in experimental atherosclerosis in rabbit and influence of selenium supplementation

Apoptosis is a ubiquitous physiological mechanism of cell death regulating tissue mass and architecture. An attempt was made in the present study to see the occurrence of apoptotic cell death in three different treatment groups of rabbits viz. Control, HFD fed and HFD + Selenium fed. Apoptotic activity as checked by in situ DNA end labelling (TUNEL Assay) revealed excessive staining, mostly concentrated in plaque region both in fibrous as well as atheromatous plaque in HFD fed animals. However, in selenium (Se) supplemented animals, very little TUNEL staining could be seen, and even that confined to endothelial cells only. The control group on the other hand was totally devoid of any staining. Transmission Electron Microscopic (TEM) study also depicted the occurrence of apoptosis in aortic cells of HFD fed animals and very little in Se supplemented animals. Apoptotic activity has been discussed in relation to oxidative stress in HFD fed group. bcl-2, though an antiapoptotic oncoprotein, was found to be expressed more in atherogenic group as compared to control/HFD + Se treatment. On the whole, the study highlighted the occurrence of apoptotic process in atherosclerosis and the role of Se, a potent antioxidant, in inhibition of apoptotic process in HFD fed animals.     

The 2 micron plasmid purloins the yeast cohesin complex: a mechanism for coupling plasmid partitioning and chromosome segregation?

The yeast 2 micron plasmid achieves high fidelity segregation by coupling its partitioning pathway to that of the chromosomes. Mutations affecting distinct steps of chromosome segregation cause the plasmid to missegregate in tandem with the chromosomes. In the absence of the plasmid stability system, consisting of the Rep1 and Rep2 proteins and the STB DNA, plasmid and chromosome segregations are uncoupled. The Rep proteins, acting in concert, recruit the yeast cohesin complex to the STB locus. The periodicity of cohesin association and dissociation is nearly identical for the plasmid and the chromosomes. The timely disassembly of cohesin is a prerequisite for plasmid segregation. Cohesin-mediated pairing and unpairing likely provides a counting mechanism for evenly partitioning plasmids either in association with or independently of the chromosomes.     

Bcl-xL/Bcl-2 coordinately regulates apoptosis, cell cycle arrest and cell cycle entry

Bcl-x(L) and Bcl-2 inhibit both apoptosis and proliferation. In investigating the relationship between these two functions of Bcl-x(L) and Bcl-2, an analysis of 24 Bcl-x(L) and Bcl-2 mutant alleles, including substitutions at residue Y28 previously reported to selectively abolish the cell cycle activity, showed that cell cycle delay and anti-apoptosis co-segregated in all cases. In determining whether Bcl-2 and Bcl-x(L) act in G(0) or G(1), forward scatter and pyronin Y fluorescence measurements indicated that Bcl-2 and Bcl-x(L) cells arrested more effectively in G(0) than controls, and were delayed in G(0)-G(1) transition. The cell cycle effects of Bcl-2 and Bcl-x(L) were reversed by Bad, a molecule that counters the survival function of Bcl-2 and Bcl-x(L). When control and Bcl-x(L) cells of equivalent size and pyronin Y fluorescence were compared, the kinetics of cell cycle entry were similar, demonstrating that the ability of Bcl-x(L) and Bcl-2 cells to enhance G(0) arrest contributes significantly to cell cycle delay. Our data suggest that cell cycle effects and increased survival both result from intrinsic functions of Bcl-2 and Bcl-x(L).