Juhasz 2017 MiPschool Obergurgl

Blockade of N-methyl-D-aspartate receptors improves polymicrobial sepsis-evoked mitochondrial dysfunction in rats.

Link: MitoEAGLE

Juhasz L, Poles MZ, Tallosy SZP, Rutai A, Boros M, Vecsei L, Szabo A, Kaszaki J (2017)

Event: MiPschool Obergurgl 2017

Sepsis-related changes in oxygen dynamics and subsequent multi-organ failure are associated with mitochondrial dysfunction and depleted energy supplies [1]. Recently, N-methyl-D-aspartate receptor (NMDA-R)-mediated increase in intracellular calcium (Ca²⁺) level has been suggested as a major source for mitochondrial Ca²⁺ uptake and Ca²⁺ overload [2,3]. However, the relationship between NMDA-R–linked Ca²⁺ entry and electron transport system function is still not fully elucidated. Thus, our main goal was to investigate whether NMDA-receptor antagonists, the natural kynurenic acid (KYNA) and its synthetic analogue, SZR-72 affects mitochondrial respiration in a rodent model of peritonitis-induced sepsis (PS).

PS was induced in male Sprague Dawley rats by intraperitoneal injection of faeces (n=18, 0.6 g/kg body weight). Animals in control group were given saline only (C; n=6). NMDA-R was blocked by by either KYNA or SZR-72 (160 µmol/kg, ip. administered twice ip. 3h and 22 h after PS induction). Blood gases and haemodynamic parameters were monitored under anaesthesia and then animals were sacrificed for the assessment of cellular respiratory function. Mitochondrial Complex-I dependent (CI; glutamate/malate+ADP) and Complex-II dependent (CII; rotenone+succinate+ADP) mitochondrial oxygen consumption was assessed from liver homogenates using high-resolution respirometry (Oroboros O2k, Oroboros Instruments, Innsbruck, Austria).

We found that glutamate/malate supported LEAK respiration and succinate supported LEAK respiration decreased markedly 24 h after the induction of PS. Similarly, both CI and CII-driven OXPHOS exhibited significantly lower values in septic rats, compared to sham-operated control animals (40% and 35%, respectively). However, the PS-induced decrease in CII-linked substrate oxidation and CII-linked OXPHOS capacity were markedly restored either by KYNA (72%) or SZR-72 (90%) while CI-linked mitochondrial respiratory function was only affected by SZR-72 administration. In addition, electron transport coupled to ATP synthesis evaluated by respiratory control ratio, observed to be higher in SZR-72 treated rats (RCR: 30%).

Our hypothesis suggests that inhibition of NMDA receptors, perhaps through the regulation of intramitochondrial Ca²⁺ pool and/or by attenuating the overproduction of reactive oxygen species, may modulate mitochondrial respiration and improve ADP utilisation to produce ATP.

• Bioblast editor: Kandolf G • O2k-Network Lab: HU Szeged Boros M

Labels: MiParea: Respiration  Pathology: Other 

Organism: Rat  Tissue;cell: Liver  Preparation: Homogenate 

Regulation: Calcium  Coupling state: LEAK, OXPHOS  Pathway: N, S  HRR: Oxygraph-2k  Event: D1, Oral 

Affiliations

Juhász L(1), Poles MZ(1), Tallósy SZP(1), Rutai A(1), Boros M(1), Vécsei L(2), Szabó A(1), Kaszaki J(1)

1. Univ Szeged, Inst Surgical Research
2. Univ Szeged, Dept Neurol.- [email protected]

References and support

1. Singer M (2014) The role of mitochondrial dysfunction in sepsis-induced multi-organ failure. Virulence 5:66-72.
2. Duan Y, Gross RA, Sheu SS (2007) Ca²⁺-dependent generation of mitochondrial reactive oxygen species serves as a signal for poly(ADP-ribose) polymerase-1 activation during glutamate excitotoxicity. J Physiol 585:741-58.
3. Pinto BB, Dyson A, Umbrello M, Carré JE, Ritter C, Clatworthy I, Duchen MR, Singer M (2017) Improved Survival in a long term-model of sepsis is associated with reduced mitochondrial calcium uptake despite increased energetic demand. Crit Care Med 45:e840-48.

Financial support: NKFIH K116689, GINOP-2.3.2-15-2016-00034