Protein stability and the evolution of the cell membrane

Analysis of cholesterol-recognition motifs of the plasma membrane Ca2+-ATPase

The plasma membrane Ca2+-ATPase (PMCA) is crucial for the fine tuning of intracellular calcium levels in eukaryotic cells. In this study, we show the presence of CARC sequences in all human and rat PMCA isoforms and we performed further analysis by molecular dynamics simulations. This analysis focuses on PMCA1, containing three CARC motifs, and PMCA4, with four CARC domains. In PMCA1, two CARC motifs reside within transmembrane domains, while the third is situated at the intracellular interface. The simulations depict more stable RMSD values and lower RMSF fluctuations in the presence of cholesterol, emphasizing its potential stabilizing effect. In PMCA4, a distinct dynamic was found. Notably, the total energy differences between simulations with cholesterol and phospholipids are pronounced in PMCA4 compared to PMCA1. RMSD values for PMCA4 indicate a more energetically favorable conformation in the presence of cholesterol, suggesting a robust interaction between CARCs and this lipid in the membranes. Furthermore, RMSF analysis for CARCs in both PMCA isoforms exhibit lower values in the presence of cholesterol compared to POPC alone. The analysis of H-bond occupancy and total energy values strongly suggests the potential interaction of CARCs with cholesterol. Given the crucial role of PMCAs in physiological calcium regulation and their involvement in diverse pathological processes, this study underscores the significance of CARC motifs and their interaction with cholesterol in elucidating PMCA function. These insights into the energetic preferences associated with CARC-cholesterol interactions offer valuable implications for understanding PMCA function in maintaining calcium homeostasis and addressing potential associated pathologies.

Moderation of doxorubicin-induced nephrotoxicity in Wistar rats by aqueous leaf-extracts of Chromolaena odorata and Tridax procumbens

BACKGROUND

The major draw-back of doxorubicin's use in chemotherapy is its toxicity on various organs including the kidneys. This study investigated the potential protective role of aqueous leaf-extracts of Chromolaena odorata and Tridax procumbens against nephrotoxicity induced by doxorubicin.

METHODS

To this end, their impact on plasma biomarkers of kidney function, as well as renal lipid profile, biomarkers of oxidative stress, electrolyte profile and activities of renal ATPases was monitored in doxorubicin treated rats. Metformin (250 mg/kg body weight, orally) and the extracts (50, 75 and 100 mg/kg, orally) were daily administered for 14 days; while nephrotoxicity was induced with doxorubicin (15 mg/kg, intra-peritioneally), once on the 12th day of study.

RESULTS

The plasma concentrations of creatinine, and urea; as well as the renal malondialdehyde, cholesterol, calcium and sodium concentrations in the Test control, were significantly (P < .05) higher than those of all the other groups. However, the renal concentrations of ascorbic acid, chloride, magnesium and potassium, and the renal activities of catalase, glutathione peroxidase superoxide dismutase, Ca2+-ATPase, Mg2+-ATPase and Na+,K+-ATPase in the Test control were significantly (P < .05) lower than those of all the other groups.

CONCLUSIONS

Pre-treatment with the extracts and metformin boosted endogenous antioxidants, and prevented doxorubicin-induced renal damage, as indicated by the attenuation of doxorubicin-induced renal oxidative stress, as well as the attenuation of doxorubicin-induced adverse alterations in renal cholesterol, ATPases and electrolyte balance, and plasma biomarkers of kidney function, and keeping them at near-normal values.

Cholesterol: recapitulation of its active role during liver regeneration

Liver regeneration is a compensatory hyperplasia produced by several stimuli that promotes proliferation in order to provide recovery of the liver mass and architecture. This process involves complex signalling cascades that receive feedback from autocrine and paracrine pathways, recognized by parenchymal as well as non-parenchymal cells. Nowadays the dynamic role of lipids in biological processes is widely recognized; however, a systematic analysis of their importance during liver regeneration is still missing. Therefore, in this review we address the role of lipids including the bioactive ones such as sphingolipids, but with special emphasis on cholesterol. Cholesterol is not only considered as a structural component but also as a relevant lipid involved in the control of the intermediate metabolism of different liver cell types such as hepatocytes, hepatic stellate cells and Kupffer cells. Cholesterol plays a significant role at the level of specific membrane domains, as well as modulating the expression of sterol-dependent proteins. Moreover, several enzymes related to the catabolism of cholesterol and whose activity is down regulated are related to the protection of liver tissue from toxicity during the process of regeneration. This review puts in perspective the necessity to study and understand the basic mechanisms involving lipids during the process of liver regeneration. On the other hand, the knowledge acquired in this area in the past years, can be considered invaluable in order to provide further insights into processes such as general organogenesis and several liver-related pathologies, including steatosis and fibrosis.

Lipid raft redox signaling: molecular mechanisms in health and disease

Lipid rafts, the sphingolipid and cholesterol-enriched membrane microdomains, are able to form different membrane macrodomains or platforms upon stimulations, including redox signaling platforms, which serve as a critical signaling mechanism to mediate or regulate cellular activities or functions. In particular, this raft platform formation provides an important driving force for the assembling of NADPH oxidase subunits and the recruitment of other related receptors, effectors, and regulatory components, resulting, in turn, in the activation of NADPH oxidase and downstream redox regulation of cell functions. This comprehensive review attempts to summarize all basic and advanced information about the formation, regulation, and functions of lipid raft redox signaling platforms as well as their physiological and pathophysiological relevance. Several molecular mechanisms involving the formation of lipid raft redox signaling platforms and the related therapeutic strategies targeting them are discussed. It is hoped that all information and thoughts included in this review could provide more comprehensive insights into the understanding of lipid raft redox signaling, in particular, of their molecular mechanisms, spatial-temporal regulations, and physiological, pathophysiological relevances to human health and diseases.