Effects of alpha-ketoglutarate on neutrophil intracellular amino and alpha-keto acid profiles and ROS production.

The aim of this study was to determine the effects of alpha-ketoglutarate on neutrophil (PMN), free alpha-keto and amino-acid profiles as well as important reactive oxygen species (ROS) produced [superoxide anion (O(2) (-)), hydrogen peroxide (H(2)O(2))] and released myeloperoxidase (MPO) activity. Exogenous alpha-ketoglutarate significantly increased PMN alpha-ketoglutarate, pyruvate, asparagine, glutamine, asparatate, glutamate, arginine, citrulline, alanine, glycine and serine in a dose as well as duration of exposure dependent manner. Additionally, in parallel with intracellular alpha-ketoglutarate changes, increases in O(2) (-) formation, H(2)O(2)-generation and MPO activity have also been observed. We therefore believe that alpha-ketoglutarate is important for affecting PMN "susceptible free amino- and alpha-keto acid pools" although important mechanisms and backgrounds are not yet completely explored. Moreover, our results also show very clearly that changes in intragranulocytic alpha-ketoglutarate levels are relevant metabolic determinants in PMN nutrition considerably influencing and modulating the magnitude and quality of the granulocytic host defense capability as well as production of ROS.

Which mechanisms are involved in taurine-dependent granulocytic immune response or amino- and alpha-keto acid homeostasis?

We examined the effects of beta-alanine (taurine analogue and taurine transport antagonist), taurine (regarding its role in neutrophil (PMN) immunonutrition) and taurine combined either with L-NAME (inhibitor of *NO-synthase), SNAP (*NO donor), DON (glutamine-analogue and inhibitor of glutamine-requiring enzymes), DFMO (inhibitor of ornithine-decarboxylase) and beta-alanine on neutrophil amino- and alpha-keto acid profiles or important PMN immune functions in order to establish whether taurine transport-, nitric oxide-, glutamine- or ornithine-dependent mechanisms are involved in any of the taurine-induced effects. According to the present findings, the taurine-mediated effect appears to be based primarily on a modulation of important transmembraneous transport mechanisms and only secondarily on directly or indirectly induced modifications in intragranulocytic amino- and alpha-keto acid homoeostasis or metabolism. Although a direct relation to the parallel observed immunological modifications can only be presumed, these results show very clearly that compositional modifications in the free intragranulocytic amino- and alpha keto-acid pools coinciding with changes in intragranulocytic taurine levels are relevant metabolic determinants that can significantly influence the magnitude and quality of the granulocytic immune response.

Alterations in neutrophil (PMN) free intracellular alpha-keto acid profiles and immune functions induced by L-alanyl-L-glutamine, arginine or taurine.

The objective of this study was to determine the dose as well as duration of exposure-dependent effects of L-alanyl-L-glutamine, arginine or taurine on polymorphonuclear neutrophil (PMN) free alpha-keto acid profiles and, in a parallel study, on PMN immune functions. Exogenous L-alanyl-L-glutamine significantly increased PMN alpha-ketoglutarate, pyruvate PMN superoxide anion (O2-) generation, hydrogen peroxide (H2O2) formation and released myeloperoxidase (MPO) activity. Arginine also led to significant increases in alpha-ketoglutarate, pyruvate, MPO release and H2O2 generation. Formation of O2- on the other hand was decreased by arginine. Incubation with taurine resulted in lower intracellular pyruvate and alpha-ketobutyrate levels, decreased O2- and H2O2 formation and a concomitant significantly increased MPO activity. We therefore believe that considerable changes in PMN free-alpha-keto-acid profiles, induced for example by L-alanyl-L-glutamine, arginine or taurine, may be one of the determinants in cell nutrition that considerably modulates the immunological competence of PMN.

Benzodiazepine receptor-dependent modulation of neutrophil (PMN) free amino- and alpha-keto acid profiles or immune functions.

We have examined the effects of midazolam, Ro 5-4864 (agonist for "peripheral" [p] benzodiazepine receptors [BR]), PK 11195 (antagonist for pBR), flumazenil (antagonist for "central" BR), naloxone (antagonist for opiate receptors) and the combination of midazolam and Ro 5-4864, PK 11195, flumazenil or naloxone on intracellular amino- and alpha-keto acids and the immune function markers superoxide anion (O(2)(-)), hydrogen peroxide (H(2)O(2)) and released myeloperoxidase (MPO) activity in neutrophils (PMN). Only midazolam and Ro 5-4864 led to significant changes in the dynamic PMN free amino- and alpha-keto acid pools. Concerning PMN immune function markers, midazolam and Ro 5-4864 significantly decreased O(2)(-) and H(2)O(2) formation and released MPO. When midazolam and Ro 5-4864 were applied together they appeared to act additively. Pre-incubation with PK 11195 partially neutralized the midazolam effects whereas flumazenil or naloxone showed no effects. We therefore believe that pBR are involved in the signal transmission of anesthetic-induced cellular metabolic changes in PMN.