The lysyl oxidase like 2/3 enzymatic inhibitor,PXS‐5153A,reduces crosslinks and ameliorates fibrosis

Fibrosis is characterized by the excessive deposition of extracellular matrix and crosslinked proteins, in particular collagen and elastin, leading to tissue stiffening and disrupted organ function. Lysyl oxidases are key players during this process, as they initiate collagen crosslinking through the oxidation of the ε‐amino group of lysine or hydroxylysine on collagen side‐chains, which subsequently dimerize to form immature, or trimerize to form mature, collagen crosslinks. The role of LOXL2 in fibrosis and cancer is well documented, however the specific enzymatic function of LOXL2 and LOXL3 during disease is less clear. Herein, we describe the development of PXS‐5153A, a novel mechanism based, fast‐acting, dual LOXL2/LOXL3 inhibitor, which was used to interrogate the role of these enzymes in models of collagen crosslinking and fibrosis. PXS‐5153A dose‐dependently reduced LOXL2‐mediated collagen oxidation and collagen crosslinking in vitro. In two liver fibrosis models, carbon tetrachloride or streptozotocin/high fat diet‐induced, PXS‐5153A reduced disease severity and improved liver function by diminishing collagen content and collagen crosslinks. In myocardial infarction, PXS‐5153A improved cardiac output. Taken together these results demonstrate that, due to their crucial role in collagen crosslinking, inhibition of the enzymatic activities of LOXL2/LOXL3 represents an innovative therapeutic approach for the treatment of fibrosis.     

Protein kinase C regulation of neuronal zinc signaling mediates survival during preconditioning

Sub-lethal activation of cell death processes initiate pro-survival signaling cascades. As intracellular Zn²⁺ liberation mediates neuronal death pathways, we tested whether a sub-lethal increase in free Zn²⁺ could also trigger neuroprotection. Neuronal free Zn²⁺ transiently increased following preconditioning, and was both necessary and sufficient for conferring excitotoxic tolerance. Lethal exposure to NMDA led to a delayed increase in Zn²⁺ that contributed significantly to excitotoxicity in non-preconditioned neurons, but not in tolerant neurons, unless preconditioning-induced free Zn²⁺ was chelated. Thus, preconditioning may trigger the expression of Zn²⁺-regulating processes, which, in turn, prevent subsequent Zn²⁺-mediated toxicity. Indeed, preconditioning increased Zn²⁺-regulated gene expression in neurons. Examination of the molecular signaling mechanism leading to this early Zn²⁺ signal revealed a critical role for protein kinase C (PKC) activity, suggesting that PKC may act directly on the intracellular source of Zn²⁺. We identified a conserved PKC phosphorylation site at serine-32 (S32) of metallothionein (MT) that was important in modulating Zn²⁺-regulated gene expression and conferring excitotoxic tolerance. Importantly, we observed increased PKC-induced serine phosphorylation in immunopurified MT1, but not in mutant MT1(S32A). These results indicate that neuronal Zn²⁺ serves as an important, highly regulated signaling component responsible for the initiation of a neuroprotective pathway.     

Dynamics of DNA ejection from bacteriophage

The ejection of DNA from a bacterial virus (i.e., phage) into its host cell is a biologically important example of the translocation of a macromolecular chain along its length through a membrane. The simplest mechanism for this motion is diffusion, but in the case of phage ejection a significant driving force derives from the high degree of stress to which the DNA is subjected in the viral capsid. The translocation is further sped up by the ratcheting and entropic forces associated with proteins that bind to the viral DNA in the host cell cytoplasm. We formulate a generalized diffusion equation that includes these various pushing and pulling effects and make estimates of the corresponding speedups in the overall translocation process. Stress in the capsid is the dominant factor throughout early ejection, with the pull due to binding particles taking over at later stages. Confinement effects are also investigated, in the case where the phage injects its DNA into a volume comparable to the capsid size. Our results suggest a series of in vitro experiments involving the ejection of DNA into vesicles filled with varying amounts of binding proteins from phage whose state of stress is controlled by ambient salt conditions or by tuning genome length.     

Parasite loads are higher in the tropics: temperate to tropical variation in a single host-parasite system

Parasites are important selective forces upon the evolutionary ecology of their hosts. At least one hypothesis suggests that high species diversity in the tropics is associated with higher parasite abundance in tropical climates. Few studies, however, have directly assessed whether parasite abundance is higher in the tropics. To address this question, it is ideal, although seldom achievable, to compare parasite abundance in a single species that occurs over a geographical area including both temperate and tropical regions. We examined variation in blood parasite abundance in seven populations of a single lizard host species ( Eulamprus quoyii ) using a transect that spans temperate and tropical climates. Parasite prevalence (proportion of the host population infected) showed no geographical pattern. Interestingly though, parasite load was higher in lizard populations in the tropics, and was related to mean annual temperature, but not to rainfall. We speculate that in this system the relationship between latitude and parasite load is most likely due to variation in host life history over their geographic range.     

Roles of structure and structural dynamics in the antibody recognition of the allergen proteins: an NMR study on Blomia tropicalis major allergen

Blo t 5 is the major allergen from Blomia tropicalis mites and shows strong IgE reactivity with up to 90% of asthmatic and rhinitis patients' sera. The NMR solution structure of Blo t 5 comprises three long alpha helices, forming a coiled-coil, triple-helical bundle with a left-handed twist. TROSY-NMR experiments were used to study Blo t 5 interaction with the Fab' of a specific monoclonal antibody, mAb 4A7. The mAb epitope comprises two closely spaced surfaces, I and II, connected by a sharp turn and bearing critical residues Asn46 and Lys47 on one surface, and Lys54 and Arg57 on the other. This discontinuous epitope overlaps with the human IgE epitope(s) of Blo t 5. Epitope surface II is further predicted to undergo conformational exchange in the millisecond to microsecond range. The results presented are critical for the design of a hypoallergenic Blo t 5 for efficacious immunotherapy of allergic diseases.     

A novel mTOR inhibitor is efficacious in a murine model of colitis

Ulcerative colitis is an autoimmune-inflammatory disease characterized by increased proliferation of colonic epithelial cells, dysregulation of signal transduction pathways, elevated mucosal T cell activation, increased production of proinflammatory cytokines, and enhanced leukocyte infiltration into colonic interstitium. Several compounds that possess antiproliferative properties and/or inhibit cytokine production exhibit a therapeutic effect in murine models of colitis. Mammalian target of rapamycin (mTOR), a protein kinase regulating cell proliferation, is implicated in colon carcinogenesis. In this study, we report that a novel haloacyl aminopyridine-based molecule (P2281) is a mTOR inhibitor and is efficacious in a murine model of human colitis. In vitro studies using Western blot analysis and cell-based ELISA assays showed that P2281 inhibits mTOR activity in colon cancer cells. In vitro and in vivo assays of proinflammatory cytokine production revealed that P2281 diminishes induced IFN-gamma production but not TNF-alpha production, indicating preferential inhibitory effects of P2281 on T cell function. In the dextran sulfate sodium (DSS) model of colitis, 1) macroscopic colon observations demonstrated that P2281 significantly inhibited DSS-induced weight loss, improved rectal bleeding index, decreased disease activity index, and reversed DSS-induced shortening of the colon; 2) histological analyses of colonic tissues revealed that P2281 distinctly attenuated DSS-induced edema, prominently diminished the leukocyte infiltration in the colonic mucosa, and resulted in protection against DSS-induced crypt damage; and 3) Western blot analysis showed that P2281 blocks DSS-induced activation of mTOR. Collectively, these results provide direct evidence that P2281, a novel mTOR inhibitor, suppresses DSS-induced colitis by inhibiting T cell function and is a potential therapeutic for colitis. Given that compounds with anticancer activity show promising anti-inflammatory efficacy, our findings reinforce the cross-therapeutic functionality of potential drugs.     

Discovery of adamantane based highly potent HDAC inhibitors

Herein, we report the development of highly potent HDAC inhibitors for the treatment of cancer. A series of adamantane and nor-adamantane based HDAC inhibitors were designed, synthesized and screened for the inhibitory activity of HDAC. A number of compounds exhibited GI₅₀ of 10-100 nM in human HCT116, NCI-H460 and U251 cancer cells, in vitro. Compound 32 displays efficacy in human tumour animal xenograft model.     

In vitro evolved non-aggregating and thermostable lipase: structural and thermodynamic investigation

Rational and in vitro evolutionary approaches to improve either protein stability or aggregation resistance were successful, but empirical rules for simultaneous improvement of both stability and aggregation resistance under denaturing conditions are still to be ascertained. We have created a robust variant of a lipase from Bacillus subtilis named “6B” using multiple rounds of in vitro evolution. T_m and optimum activity temperature of 6B is 78 °C and 65 °C, respectively, which is ∼ 22 °C and 30 °C higher than that of wild-type lipase. Most significantly, 6B does not aggregate upon heating. Physical basis of remarkable thermostability and non-aggregating behavior of 6B was explored using X-ray crystallography, NMR and differential scanning calorimetry. Our structural investigations highlight the importance of tightening of mobile regions of the molecule such as loops and helix termini to attain higher thermostability. Accordingly, NMR studies suggest a very rigid structure of 6B lipase. Further investigation suggested that reduction/perturbation of the large hydrophobic patches present in the wild-type protein structure, decreased propensity of amino acid sequence for aggregation and absence of aggregation-prone intermediate during thermal unfolding of 6B can account for its resistance to aggregation. Overall, our study suggest that better anchoring of the loops with the rest of the protein molecule through mutations particularly on the sites that perturb/disturb the exposed hydrophobic patches can simultaneously increase protein stability and aggregation resistance.     

Avian scavengers and the threat from veterinary pharmaceuticals

Veterinary use of the non-steroidal anti-inflammatory drug diclofenac on domesticated ungulates caused populations of resident Gyps vultures in the Indian sub-continent to collapse. The birds died when they fed on carrion from treated animals. Veterinary diclofenac was banned in 2006 and meloxicam was advocated as a ‘vulture-safe’ alternative. We examine the effectiveness of the 2006 ban, whether meloxicam has replaced diclofenac, and the impact of these changes on vultures. Drug residue data from liver samples collected from ungulate carcasses in India since 2004 demonstrate that the prevalence of diclofenac in carcasses in 2009 was half of that before the ban and meloxicam prevalence increased by 44%. The expected vulture death rate from diclofenac per meal in 2009 was one-third of that before the ban. Surveys at veterinary clinics show that diclofenac use in India began in 1994, coinciding with the onset of rapid Gyps declines ascertained from measured rates of declines. Our study shows that one pharmaceutical product has had a devastating impact on Asia''s vultures. Large-scale research and survey were needed to detect, diagnose and quantify the problem and measure the response to remedial actions. Given these difficulties, other effects of pharmaceuticals in the environment may remain undetected.     

Abnormal Mitochondrial L-Arginine Transport Contributes to the Pathogenesis of Heart Failure and Rexoygenation Injury

Background

Impaired mitochondrial function is fundamental feature of heart failure (HF) and myocardial ischemia. In addition to the effects of heightened oxidative stress, altered nitric oxide (NO) metabolism, generated by a mitochondrial NO synthase, has also been proposed to impact upon mitochondrial function. However, the mechanism responsible for arginine transport into mitochondria and the effect of HF on such a process is unknown. We therefore aimed to characterize mitochondrial L-arginine transport and to investigate the hypothesis that impaired mitochondrial L-arginine transport plays a key role in the pathogenesis of heart failure and myocardial injury.

Methods and Results

In mitochondria isolated from failing hearts (sheep rapid pacing model and mouse Mst1 transgenic model) we demonstrated a marked reduction in L-arginine uptake (p<0.05 and p<0.01 respectively) and expression of the principal L-arginine transporter, CAT-1 (p<0.001, p<0.01) compared to controls. This was accompanied by significantly lower NO production and higher 3-nitrotyrosine levels (both p<0.05). The role of mitochondrial L-arginine transport in modulating cardiac stress responses was examined in cardiomyocytes with mitochondrial specific overexpression of CAT-1 (mtCAT1) exposed to hypoxia-reoxygenation stress. mtCAT1 cardiomyocytes had significantly improved mitochondrial membrane potential, respiration and ATP turnover together with significantly decreased reactive oxygen species production and cell death following mitochondrial stress.

Conclusion

These data provide new insights into the role of L-arginine transport in mitochondrial biology and cardiovascular disease. Augmentation of mitochondrial L-arginine availability may be a novel therapeutic strategy for myocardial disorders involving mitochondrial stress such as heart failure and reperfusion injury.