Ekspresija CYP2E1 u testisima štakora i alkoholom prouzrokovane promjene indeksa spermatogeneze i kolagena tipa I

This study is a complex investigation of alcohol-mediated changes in CYP2E1 mRNA and protein expression in the testes, as well as spermatogenesis indices and type I collagen amino acid contents, in male rats. Wistar albino male rats were divided into two groups: I – control (intact animals), II – experimental (chronic alcoholism, exposure to a 15 % ethanol aqueous solution during 150 days). The destructive changes in the spermatogenic epithelium were accompanied by a decrease in sperm number and motility time. CYP2E1 mRNA and protein expression were elevated in the testes 3 and 1.4 times, respectively. Also, significantly lower contents of lysine, glutamic acid, serine, proline, alanine, valine, and phenylalanine residues accompanied by an increase of hydroxyproline, glycine, and threonine residue contents were detected in the skin type I collagen of the experimental group. Chronic ethanol consumption caused testicular failure along with an overexpression of CYP2E1 mRNA and protein in the testes as well as quantitative changes in type I collagen amino acid contents. The profound alcohol-mediated changes in collagen type I amino acid contents may have affected the spermatogenic epithelium state. The modulation of testicular cytochrome P450 2E1 mRNA and protein expression could change the functioning of this isozyme in target organs and take part in the mechanism of ethanol gonadotoxicity.Ovo istraživanje proučava alkoholom uzrokovane promjene u ekspresiji CYP2E1 mRNA i bjelančevina iz testisa, indeksu spermatogeneze i aminokiselinskom sastavu kolagena tipa I u muških štakora. Albino štakori tipa Wistar podijeljeni su u dvije skupine: I – kontrolna, II – eksperimentalna (kronični alkoholizam, izloženi 150 dana 15-postotnoj vodenoj otopini etanola). Destruktivne promjene u spermatogenetskom epitelu popraćene su smanjenjem broja i pokretljivosti spermija. Ekspresija mRNA gena CYP2E1 i bjelančevina bila je povišena u testisima 3, odnosno 1,4 puta. Također, u kolagenu tipa I ustanovljene su značajno manje količine lizina, glutaminske kiseline, serina, prolina, alanina, valina i fenilalanina, te veće količine ostataka hidroksiprolina, glicina i treonina. Kronična konzumacija etanola uzrokovala je otkazivanje testisa uz izraženu ekspresiju mRNA CYP2E1 i bjelančevina u testisima, te kvantitativne promjene u aminokiselinama kolagena tipa I. Izražene alkoholom prouzrokovane promjene mogle su utjecati na spermatogenetski epitel. Modulacija ekspresije mRNA testikularnog citokroma P450-2E1 i bjelančevina mogla bi promijeniti djelovanje ovoga izozima u ciljnim organima te sudjelovati u mehanizmu gonadotoksičnosti etanola

Fibril breaking accelerates α-synuclein fibrillization

The formation of amyloid fibrils of α-synuclein (αSyn), the key protein in Parkinsons disease, is an autocatalytic process that is seeded by mature αSyn fibrils. Based on systematic measurements of the dependence of the fibril growth rate on the concentrations of monomers and preformed fibrillar seeds, we propose a mechanism of αSyn aggregation that includes monomer binding to fibril ends and secondary nucleation by fibril breaking. The model explains the increase of the αSyn aggregation rate under shaking conditions and the exponential increase in the fraction of fibrillar protein at the initial stages of αSyn aggregation. The proposed autocatalytic mechanism also accounts for the high variability in the aggregation lag time. The rate constant of monomer binding to the ends of fibrils, k+ ∼1.3 mM-1 s-1, was estimated from the aggregation rate and previously reported average fibril lengths. From the aggregation rates at low concentrations the binding of monomeric αSyn to fibrils was found to be almost irreversible, with an equilibrium dissociation constant (Kd) smaller than 3 μM