Heterotropic roles of divalent cations in the establishment of allostery and affinity maturation of integrin αXß2.

Allosteric activation and silencing of leukocyte ß2-integrins transpire through cation-dependent structural changes, which mediate integrin biosynthesis and recycling, and are essential to designing leukocyte-specific drugs. Stepwise addition of Mg2+ reveals two mutually coupled events for the αXß2 ligand-binding domain-the αX I-domain-corresponding to allostery establishment and affinity maturation. Electrostatic alterations in the Mg2+-binding site establish long-range couplings, leading to both pH- and Mg2+-occupancy-dependent biphasic stability change in the αX I-domain fold. The ligand-binding sensorgrams show composite affinity events for the αX I-domain accounting for the multiplicity of the αX I-domain conformational states existing in the solution. On cell surfaces, increasing Mg2+ concentration enhanced adhesiveness of αXß2. This work highlights how intrinsically flexible pH- and cation-sensitive architecture endows a unique dynamic continuum to the αI-domain structure on the intact integrin, thereby revealing the importance of allostery establishment and affinity maturation in both extracellular and intracellular integrin events.

p-Cymene Modulate Oxidative Stress and Inflammation in Murine Macrophages: Potential Implication in Atherosclerosis.

BACKGROUND: p-Cymene (p-CYM) is a common chemical used in air fresheners. OBJECTIVE: The study was designed to investigate the molecular effect of p-CYM on macrophages. MATERIALS AND METHODS: Macrophages (RAW 264.7) were treated with p-CYM (50 uM/L, 150 uM/L and 250 uM/L) for 6 hours, and 24 hours). Gene involved in inflammation, such as the Tumor Necrosis Factor-alpha (TNF-α), and the Monocyte Chemoattractant Protein-1 (MCP-1) and other genes known for their antioxidant activity such as the Paraoxonase 1 (PON-1) were analyzed. RESULTS: Cells treated with p-CYM have shown 30% up-regulation of MCP-1 after 24 hour of exposure; and also a differential up-regulation of TNF-α. However, treatment with p-CYM has resulted in a considerable (37%) dose-dependent downregulation of PON-1 after 24 hours of exposure. PON-1 is known for its antioxidant properties protecting High-Density Lipoproteins (HDL) from oxidation. CONCLUSION: Our findings demonstrate that exposure to p-CYM over time promotes oxidative stress by downregulating antioxidants genes as shown in PON-1 and also stimulates inflammation, a key process during the initiation and progression of atherosclerosis.

Screening of Focused Compound Library Targeting Liver X Receptors in Pancreatic Cancer Identified Ligands with Inverse Agonist and Degrader Activity.

Pancreatic ductal adenocarcinoma (PDAC) is the predominant form of pancreatic cancer. PDACs harbor oncogenic mutations in the KRAS gene, and ongoing efforts to directly target its mutant protein product to inhibit tumor growth are a priority not only in pancreatic cancer but in other malignancies such as lung and colorectal cancers where KRAS is also commonly mutated. An alternative strategy to directly targeting KRAS is to identify and target druggable receptors involved in dysregulated cancer hallmarks downstream of KRAS dysregulation. Liver X receptors (LXRs) are members of the nuclear receptor family of ligand-modulated transcription factors and are involved in the regulation of genes which function in key cancer-related processes, including cholesterol transport, lipid and glucose metabolism, and inflammatory and immune responses. Modulation of LXRs via small molecule ligands has emerged as a promising approach for directly targeting tumor cells or the stromal and immune cells within the tumor microenvironment. We have previously shown that only one of the two LXR subtypes (LXRß) is expressed in pancreatic cancer cells, and targeting LXR with available synthetic ligands blocked the proliferation of PDAC cells and tumor formation. In a screen of a focused library of drug-like small molecules predicted to dock in the ligand-binding pocket of LXRß, we identified two novel LXR ligands with more potent antitumor activity than current LXR agonists used in our published studies. Characterization of the two lead compounds (GAC0001E5 and GAC0003A4) indicates that they function as LXR inverse agonists which inhibit their transcriptional activity. Prolonged treatments with novel ligands further revealed their function as LXR "degraders" which significantly reduced LXR protein levels in all three PDAC cell lines tested. These findings support the utility of these novel inhibitors in basic research on ligand design, allosteric mechanisms, and LXR functions and their potential application as treatments for advanced pancreatic cancer and other recalcitrant malignancies.

Targeting the Role of Lipoprotein (a) in Stroke.

BACKGROUND: Stroke is the third leading cause of death in the United States, behind only heart disease and cancer, with over 140,000 associated deaths per year. METHODS: Considerable research is ongoing to examine the role of modifiable risk factors which may cause or contribute to stroke. Although age and family history are generally considered to be the major risk factors, there are several modifiable and non-modifiable risk factors that are linked to the pathogenesis of a stroke. Lipoprotein (a), or Lp(a), is a type of low-density lipoprotein containing an integral apolipoprotein B100 (apoB100) component with an attached apolipoprotein A-1 (ApoA-1) isoform via a disulfide linkage. Lp(a) metabolism is of great interest as it sheds light on its role in pathogenesis of not only cardiovascular disorders but also stroke. Although Lp(a) has been identified as an "LDL-like particle", its metabolism differs from low density lipoprotein (LDL). Despite some ambiguity in the literature regarding the causative effect of Lp(a) on stroke, there are clear associations of high plasma Lp(a) concentration and risk of stroke. Furthermore, the small isoforms of ApoA-1-containing lipoproteins have been shown to increase atherogenicity in atherosclerotic patients. CONCLUSION: Currently, there is little research examining the importance of small molecule Lp(a) distribution and risk for stroke, both on a first-case and recurrent basis. Understanding the role of Lp (a) in stroke requires investigating its molecular mechanisms particularly the key microRNA (s) components that control its expression and function (s). Therefore, the main objective of this review is to discuss the broader link between Lp(a) and stroke and to identify opportunities for future investigation and potential research prospects on the role of Lp (a) in stroke.