Possibilities of cognitive-affective disorders correction in patients with atopic dermatitis using selanc regulatory peptide

Objective: To evaluate the efficacy of the selank regulatory peptide against cognitive-affective disorders in patients with atopic dermatitis (AD). Material and methods. The analysis of cognitive-affective disorders of 65 patients with atopic dermatitis (AD), randomized into 2 statistically comparable groups, was carried out. Patients of the first group received basic drug therapy (BT) for AD, the second group - a combination of selank and BT (S + BT) intranasally, 2 drops in each nasal passage, 3 times a day, for 14 days. The control group consisted of 30 healthy individuals. The levels of personal (LT) and reactive (RT) anxiety, alexithymia, the level of β-endorphin in the blood, and the quality of life (QOL) before treatment and after 30 days from its start were assessed. Results. In patients with AD, the level of RT was 4.2 times higher than in the control group, RT - 3.2 times, alexithymia - 18 times. In the BT group, 30 days after the start of treatment, RT decreased 1.4 times and RT - 1.3 times. In the C+BT group, the decrease in LT and RT was equally significant - by 2.4 times. The levels of alexithymia and blood β-endorphin in the BT group did not change significantly. In the S+BT group, alexithymicity of patients decreased by 1.2 times, and the level of β-endorphin in the blood increased by 1.9 times. The quality of life index in the BT group decreased 1.2 times after 30 days from the start of therapy, and 1.7 times in the S + BT group. Conclusion. Patients with AD are characterized by the increased levels of personal and reactive anxiety and alexithymia, which reduce their quality of life. The use of the selank regulatory peptide in the complex treatment of patients with AD has a corrective effect on affective-cognitive impairment, contributing to a decrease in the levels of personal and reactive anxiety, alexithymia, increases the level of β-endorphin in the blood and improves the quality of life of patients.

Deciphering the mechanism of inhibition of SERCA1a by sarcolipin using molecular simulations

SERCA1a is an ATPase calcium pump that transports Ca2+ from the cytoplasm to the sarco/endoplasmic reticulum lumen. Sarcolipin (SLN), a transmembrane peptide, regulates the activity of SERCA1a by decreasing its Ca2+ transport rate, but its mechanism of action is still not well understood. To decipher this mechanism, we have performed normal modes analysis in the all-atom model, with the SERCA1a-SLN complex or the isolated SERCA1a embedded in an explicit membrane. The comparison of the results allowed us to provide an explanation for the action of SLN that is in good agreement with experimental observations. In our analyses, the presence of SLN locally perturbs the TM6 transmembrane helix and as a consequence modifies the position of D800, one of the key metal-chelating residues. Additionally, it reduces the flexibility of the gating residues, V304 and E309 in TM4, at the entrance of the Ca2+ binding sites, which would decrease the affinity for Ca2+. Unexpectedly, SLN has also an effect on the ATP binding site more than 35 Å away, due to the straightening of TM5, a long helix considered as the spine of the protein. The straightening of TM5 modifies the structure of the P-N linker that sits above it, and which comprises the 351DKTG354 conserved motif, resulting in an increase of the distance between ATP and the phosphorylation site. As a consequence, the turn-over rate could be affected. All this gives SERCA1a the propensity to go toward a Ca2+-deprived E2-like state in the presence of SLN and toward a Ca2+ high-affinity E1-like state in the absence of SLN, although the SERCA1a-SLN complex was crystallized in an E1-like state. In addition to a general mechanism of inhibition of SERCA1a regulatory peptides, this study also provides an insight in the conformational transition between the E2 and E1 states.Statement of SignificanceThe role of sarco/endoplasmic reticulum calcium ATPase in muscle relaxation is essential. Impairment of its function may result in either cardiac diseases, or myopathies, and also thermogenesis defects. Inhibition of the ATPase by regulatory peptide such as sarcolipin remains unclear. The structure of the ATPase in complex with this peptide was studied by all-atom normal modes analysis, an in silico technique which allows us to decipher the mechanism of inhibition of calcium transport by sarcolipin at a molecular level. Our results open the way to understanding the impact of in vivo misregulation of the ATPase activity by sarcolipin. Development of tools enhancing or preventing interaction between the ATPase and its regulatory peptide could be considered as new therapeutic approaches.

Leishmania infection triggers hepcidin-mediated proteasomal degradation of Nramp1 resulting in increased phagolysosomal iron availability

Natural resistance associated macrophage protein 1 (Nramp1) was discovered as a genetic determinant of resistance against multiple intracellular pathogens, including Leishmania. It encodes a transmembrane protein of the phago-endosomal vesicles, where it functions as an iron transporter. But how Nramp1 expression is regulated in an infected macrophage is unknown. Its role in controlling iron availability to the intracellular pathogens and in determining the final outcome of an infection also remains to be fully deciphered. Here we report that Nramp1 protein abundance undergoes temporal changes in Leishmania major infected macrophages. At 12 hours post infection, there was drastic lowering of Nramp1 level accompanied by increased phagolysosomal iron availability and enhanced parasite growth. Leishmania infection-induced downregulation of Nramp1 was found to be caused by ubiquitin-proteasome degradation pathway. In fact, blocking of Nramp1 degradation with proteasome inhibitor resulted in depletion of phagolysosomal iron pool with significant reduction in the number of intracellular parasites. Further, we uncovered that this degradation process is mediated by the iron regulatory peptide hormone hepcidin that binds to Nramp1. Interestingly, Nramp1 protein level was restored to normalcy after 30 hours of infection with a concomitant drop in the phagolysosomal iron level, which is suggestive of a host counter defense strategy to deprive the pathogen of this essential micronutrient. Taken together, our study implicates Nramp1 as a central player in the host-pathogen battle for iron. It also unravels Nramp1 as a novel partner for hepcidin. The hitherto unidentified ‘hepcidin-Nramp1 axis’ may have a broader role in regulating macrophage iron homeostasis.ImportanceLeishmania parasites are the causative agents of a group of neglected tropical diseases called leishmaniasis. They reside within the phagolysosomes of mammalian macrophages. Since iron is an essential micronutrient for survival and virulence, intracellular Leishmania must acquire it from the tightly regulated macrophage iron pool. How this challenging task is accomplished remains a fundamental question in Leishmania biology. We report here that Leishmania major infection caused ubiquitin-proteasome-mediated degradation of natural resistance associated macrophage protein 1 (Nramp1). Nramp1 being an iron exporter at the phago-endosomal membrane, its degradation resulted in increased phagolysosomal iron availability thereby stimulating parasite growth. We also uncovered that Nramp1 degradation is controlled by the iron regulatory peptide hormone hepcidin. Interestingly, at a later stage of infection, Nramp1 protein level was restored to normalcy with simultaneous depletion of phagolysosomal iron. Collectively, our study implicates Nramp1 as a central player in the host-pathogen struggle for acquiring iron.