Dilated cardiomyopathy: a new insight into the rare but common cause of heart failure

Heart Failure Reviews - Heart failure is a global health burden responsible for high morbidity and mortality with a prevalence of greater than 60 million individuals worldwide. One of the major...     

Chemokine-induced leishmanicidal activity in murine macrophages via the generation of nitric oxide

This study explored the role of the proinflammatory chemokines macrophage inflammatory protein (MIP)-1alpha and macrophage chemoattractant protein (MCP)-1 for development of antileishmanial activity. There was substantial inhibition in nitrite generation in Leishmania donovani-infected macrophages. A marked elevation of nitrite generation and induction of inducible nitric oxide (NO) synthase (iNOS) mRNA was found in chemokine-primed parasite-infected macrophages. Tumor necrosis factor-alpha, which is the priming signal for NO production, was also up-regulated under similar experimental conditions. The priming with chemokine inhibited the multiplication of L. donovani amastigotes within the intramacrophageal milieu. The antileishmanial effect of chemokines was almost completely abrogated when the macrophages were preincubated with l-N-monomethyl arginine, the specific inhibitor of iNOS. The results of this investigation suggest that the CC chemokines MIP-1alpha and MCP-1 orchestrate an antileishmanial armamentarium via the induction of an NO-mediated regulatory mechanism to control the intracellular growth and multiplication of the Leishmania protozoan.     

Effect of acute lung injury on angiotensin converting enzyme in serum, lung lavage, and effusate

The administration of an acute pulmonary edemagenic dose (ip) of thiourea to rats results in an elevation of angiotensin converting enzyme (ACE) in serum, lung lavage, and pleural effusion. The increased serum ACE corresponds to a reduction in lung ACE, but it is transient, lasting between 1 and 2 h. ACE remains elevated in lung lavage and pleural effusion for at least 4 h after the administration of thiourea.     

Synthesis,pharmacological evaluations,and molecular docking studies on a new 1,3,4,11b‐tetrahydro‐1H‐fluoreno[9,1‐cd]azepine framework: Rigidification of D1 receptor selective 1‐phenylbenzazepines and discovery of a new 5‐HT6 receptor scaffold

The novel 1,3,4,11b‐tetrahydro‐1H‐fluoreno[9,1‐cd]azepine framework, a structurally rigidified variant of the 1‐phenylbenzazepine template, was synthesized via direct arylation as a key reaction. Evaluation of the binding affinities of the rigidified compounds across a battery of serotonin, dopamine, and adrenergic receptors indicates that this scaffold unexpectedly has minimal affinity for D₁ and other dopamine receptors and is selective for the 5‐HT₆ receptor. The affinity of these systems at the 5‐HT₆ receptor is significantly influenced by electronic and hydrophobic interactions as well as the enhanced rigidity of the ligands. Molecular docking studies indicate that the reduced D₁ receptor affinity of the rigidified compounds may be due in part to weaker H‐bonding interactions between the oxygenated moieties on the compounds and specific receptor residues. Key receptor–ligand H‐bonding interactions, salt bridges, and π–π interactions appear to be responsible for the 5‐HT₆ receptor affinity of the compounds. Compounds 10 (6,7‐dimethoxy‐2,3,4,11b‐tetrahydro‐1H‐fluoreno[9,1‐cd]azepine) and 12 (6,7‐dimethoxy‐2‐methyl‐2,3,4,11b‐tetrahydro‐1H‐fluoreno[9,1‐cd]azepine) have been identified as structurally novel, high affinity (K_i = 5 nM), selective 5‐HT₆ receptor ligands.     

Understanding the frustration arising from the competition between function,misfolding, and aggregation in a globular protein

Folding and function may impose different requirements on the amino acid sequences of proteins, thus potentially giving rise to conflict. Such a conflict, or frustration, can result in the formation of partially misfolded intermediates that can compromise folding and promote aggregation. We investigate this phenomenon by studying frataxin, a protein whose normal function is to facilitate the formation of iron–sulfur clusters but whose mutations are associated with Friedreich’s ataxia. To characterize the folding pathway of this protein we carry out a Φ-value analysis and use the resulting structural information to determine the structure of the folding transition state, which we then validate by a second round of rationally designed mutagenesis. The analysis of the transition-state structure reveals that the regions involved in the folding process are highly aggregation-prone. By contrast, the regions that are functionally important are partially misfolded in the transition state but highly resistant to aggregation. Taken together, these results indicate that in frataxin the competition between folding and function creates the possibility of misfolding, and that to prevent aggregation the amino acid sequence of this protein is optimized to be highly resistant to aggregation in the regions involved in misfolding.Frustration is a general condition that arises in the presence of conflicting requirements. A system is frustrated when it is impossible to fully minimize its energy by optimizing simultaneously all of the possible interactions among its components (1). Although complex systems tend in general to exhibit frustration because of the large number and heterogeneity of their components, protein molecules are remarkable in that their folding process involves interactions that express a minimal level of frustration. According to the so-called principle of minimal frustration, the energy of proteins decreases as they explore conformations increasingly similar in structure to the native state (2). Consequently, the free energy landscape of proteins is characterized by the presence of a well-defined global minimum and very few other local minima, which are typically intermediate states along the folding pathway. This organization of conformational space normally ensures rapid and reliable folding (2–6).Proteins, however, have evolved not only to fold, but also to function. Because the evolutionary constraints that select for a given function may be in conflict with the folding process, it is possible that local frustration patterns may localize in specific regions of proteins, in particular in their active sites. Indeed, a statistical survey of different proteins has shown that frustrated interactions tend to cluster at binding sites and that such frustration decreases upon complex formation (7). Because frustration is associated with the presence of local minima in the free energy landscape, it is important to understand how proteins have evolved to minimize the possible effects associated with these local minima, which are likely to contain misfolded elements and thus to potentially give rise to aggregation.To address this question we studied frataxin, a mitochondrial protein that binds both Fe²⁺ and Fe³⁺ ions and forms a ternary complex with the two main components of the iron–sulfur cluster biogenesis machinery (8–11). This protein offers good opportunities for investigating the relationships between folding, misfolding, and disease. Indeed, its dysfunction is related to a neurodegenerative disease called Friedreich’s ataxia (12). Frataxin is also capable of binding different divalent and trivalent cations, whose recognition sites have been mapped (13). Furthermore, frataxin is involved in donating iron to ferrochelatease via direct interaction through an extended binding site involving some of the residues implicated in metal binding (14).We have previously shown that frataxin folds via a complex mechanism, which we described through a broad free energy barrier (15). This feature, which has been associated with frustration (16), allows the experimental characterization of both the early and late events of folding (16–19). In this work we explored the mechanistic details of the folding reaction of frataxin at residue-level resolution. This result was achieved by characterizing the structures of both the early and late events of folding using Φ-value analysis (20) and restrained molecular dynamics simulations (21). By analyzing the structures of the different states along the folding process we found an unexpected number of nonnative interactions that slow down folding and superpose with the highly frustrated regions, as detected by the frustratometer server (22). The nonnative regions, which display peculiar Φ values, either negative or greater than unity, were predicted on the basis of the transition state structures determined from the Φ values, and subsequently confirmed by a second round of amino acid substitutions rationally designed to probe misfolded regions along the folding pathway.The characterization of the folding pathway of frataxin and of its misfolded elements enables us to discuss the competition between folding and function and its consequences for misfolding and aggregation.     

Response to androgen therapy in patients with dyskeratosis congenita

Dyskeratosis congenita (DC) is an inherited bone marrow failure syndrome and telomere biology disorder characterized by dysplastic nails, reticular skin pigmentation and oral leucoplakia. Androgens are a standard therapeutic option for bone marrow failure in those patients with DC who are unable to undergo haematopoietic stem cell transplantation, but there are no systematic data on its use in those patients. We evaluated haematological response and side effects of androgen therapy in 16 patients with DC in our observational cohort study. Untreated DC patients served as controls. Seventy percent of treated DC patients had a haematological response with red blood cell and/or platelet transfusion independence. The expected age‐related decline in telomere length was noted in androgen‐treated patients. All treated DC patients had at least one significant lipid abnormality. Additional treatment‐related findings included a significant decrease in thyroid binding globulin, accelerated growth in pre‐pubertal children and splenic peliosis in two patients. Liver enzymes were elevated in both androgen‐treated and untreated patients, suggesting underlying liver involvement in DC. This study suggests that androgen therapy can be effectively used to treat bone marrow failure in DC, but that side effects need to be closely monitored.