Lipopolysaccharide Stimulates Mitochondrial Biogenesis via Activation of Nuclear Respiratory Factor-1

Abstract

Exposure to bacterial lipopolysaccharide (LPS) in vivo damages mitochondrial DNA (mtDNA) and interferes with mitochondrial transcription and oxidative phosphorylation (OXPHOS). Because this damage accompanies oxidative stress and is reversible, we postulated that LPS stimulates mtDNA replication and mitochondrial biogenesis via expression of factors responsive to reactive oxygen species, i.e. nuclear respiratory factor-1 (NRF-1) and mitochondrial transcription factor-A. In testing this hypothesis in rat liver, we found that LPS induces NRF-1 protein expression and activity accompanied by mRNA expression for mitochondrial transcription factor-A, mtDNA polymerase ␥, NRF-2, and single-stranded DNA-binding protein. These events restored the loss in mtDNA copy number and OXPHOS gene expression caused by LPS and increased hepatocyte mitotic index, nuclear cyclin D1 translocation, and phosphorylation of pro-survival kinase, Akt. Thus, NRF-1 was implicated in oxidant-mediated mitochondrial biogenesis to provide OXPHOS for proliferation. This implication was tested in novel mtDNA-deficient cells generated from rat hepatoma cells that overexpress NRF-1. Depletion of mtDNA ( o clones) diminished oxidant production and caused loss of NRF-1 expression and growth delay. NRF-1 expression and growth were restored by exogenous oxidant exposure indicating that oxidative stress stimulates biogenesis in part via NRF-1 activation and corresponding to recovery events after LPS-induced liver damage.

A novel endotoxin-induced pathway: upregulation of heme oxygenase 1, accumulation of free iron, and free iron-mediated mitochondrial dysfunction

“…24,40,41 However at 4 and particularly at 8 h, RC was significantly decreased, recovering at 12 h. This is in line with reports showing impaired mitochondrial function at 4 h after LPS challenge in feline, 20 and improved mitochondrial function at 16 h in rats. 17,40 We show that both a decrease in RC at 4 h and an increase later on is also valid for rats.…”

“…These data provide a mechanistic rationale for previously published articles [40][41][42][43] reporting beneficial effects of the iron chelator desferioxamine in sepsis models. Notably, the increase in hepatic intracellular iron levels was not due to decreased levels of transferrin-bound iron in blood.…”

Peroxisome Proliferator-activated Receptor γ Co-activator 1-α as a Critical Co-activator of the Murine Hepatic Oxidative Stress Response and Mitochondrial Biogenesis in Staphylococcus aureus Sepsis

“…Proteins were probed with primary antibodies to polyclonal rabbit anti-PGC-1␣ (Cayman Chemical, Ann Arbor, MI), rabbit anti-SOD-2 (Abcam, Cambridge, MA), rabbit anti-nuclear factor (erythroid-derived 2)-like 2 (Nfe2l2 H300, Santa Cruz Biotechnology, Santa Cruz, CA), rabbit antiprogrammed cell death-1 (mPD-1, AnaSpec, Fremont, CA), rabbit anti-mitofusin-2 (Mfn-2, Epitomics, Burlingame, CA), and mouse anti-NAD(P)H dehydrogenase (quinone) 1 (QR1, Santa Cruz Biotechnology). Antibodies to NRF-1, NRF-2 (GABPA), and mitochondrial transcription factor A (mtTFA) developed in rabbits were characterized in our laboratory (24). After application of primary antibodies and washing, membranes were incubated with the appropriate horseradish peroxidase-conjugated secondary antibodies (Santa Cruz Biotechnology).…”

Heme Oxygenase-1 Couples Activation of Mitochondrial Biogenesis to Anti-inflammatory Cytokine Expression

“…ChIP and DNA Binding Assays-Nuclear liver and cell extracts were prepared as described (36,37). Transcriptional activation of Nfe2l2 and MEF2A was measured using the TRANS-AM kit (Active Motif, Carlsbad, CA).…”