Modulation of glucose-related metabolic pathways controls glucose level in airway surface liquid and fight oxidative stress in cystic fibrosis cells.

Direct and indirect evidences show that elevated glucose concentrations in airway surface liquid (ASL) promote lung infection by pathogens, playing a role in the progression of the Cystic Fibrosis (CF) disease. The joint action of transporter/s for glucose and of the cellular enzymes is essential in order to try to lower ASL glucose level. Inside the cell, the glycolysis and the pentose phosphate pathway (PPP) compete for the utilization of glucose-6-phosphate (G6P), the product in which glucose, after entry within the cell and phosphorylation, is trapped. The study aims to clarify whether, modulating the activity of enzymatic proteins and/or the level of metabolites/cofactors, involved in intracellular glucose utilization, a lowering of the extracellular glucose level in CF occurs. Biochemical approaches have enabled us to understand i) how G6P is shunted between glycolysis and PPP and ii) that mitochondria, more than enzymes/cofactors participating to the two cell glucose utilization pathways, are protagonists of the scene in counteracting the high ASL glucose level as well as oxidative stress in CF.

Aberrant GSH reductase and NOX activities concur with defective CFTR to pro-oxidative imbalance in cystic fibrosis airways.

Cystic fibrosis (CF) is associated to impaired Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) channel also causing decreased glutathione (GSH) secretion, defective airway bacterial clearance and inflammation. Here we checked the main ROS-producing and ROS-scavenging enzymes as potential additional factors involved in CF pathogenesis. We found that CFBE41o-cells, expressing F508del CFTR, have increased NADPH oxidase (NOX) activity and expression level, mainly responsible of the increased ROS production, and decreased glutathione reductase (GR) activity, not dependent on GR protein level decrease. Furthermore, defective CFTR proved to cause both extracellular and intracellular GSH level decrease, probably by reducing the amount of extracellular GSH-derived cysteine required for cytosolic GSH synthesis. Importantly, we provide evidence that defective CFTR and NOX/GR activity imbalance both contribute to NADPH and GSH level decrease and ROS overproduction in CF cells.

A peptide containing residues 26-44 of tau protein impairs mitochondrial oxidative phosphorylation acting at the level of the adenine nucleotide translocator.

Having confirmed that adenovirus-mediated overexpression of NH(2)-tau fragment lacking the first 25 aminoacids evokes a potent neurotoxic effect, sustained by protracted stimulation of NMDA receptors, in primary neuronal cultures we investigated whether and how chemically synthesized NH(2)-derived tau peptides, i.e. NH(2)-26-44 and NH(2)-1-25 fragments, affect mitochondrial function. We tested both fragments on each step of the processes leading to ATP synthesis via oxidative phosphorylation: i) electron flow via the respiratory chain from physiological substrates to oxygen with the activity of each individual complex of the respiratory chain investigated in some detail, ii) membrane potential generation arising from externally added succinate and iii) the activity of both the adenine nucleotide translocator and iv) ATP synthase. Oxidative phosphorylation is not affected by NH(2)-1-25 tau fragment, but dramatically impaired by NH(2)-26-44 tau fragment. Both cytochrome c oxidase and the adenine nucleotide translocator are targets of NH(2)-26-44 tau fragment, but adenine nucleotide translocator is the unique mitochondrial target responsible for impairment of oxidative phosphorylation by the NH(2)-26-44 tau fragment, which then exerts deleterious effects on cellular availability of ATP synthesized into mitochondria.