Biology subjects

Beutner, G.

Publications and source records attributed to Beutner, G..

3 recordsLinked to original sources

bioRxiv2025

Low Magnetic Fields Stimulate Cardiac Mitochondrial Bioenergetics with a Bell-Shaped Response: Possibly Via a Radical Pair Mechanism

Studies have shown that low magnetic fields (LMFs) of less than 1 x 10-3 Tesla (T) affect numerous biological events, including bacteria and plant growth, bird migration, and human brain activity. On a cellular level, LMFs affect ion channel activities, intracellular Ca2+ concentrations, and mitochondrial reactive oxygen species (mROS) generation. However, the mechanisms that could account for these effects are controversial. Here, we show that applying a static LMF, ranging from [~]2.7 x 10-4 to [~]1.9 x 10-3 T, to mitochondria isolated from adult rat hearts produced a bell-shaped increase in maximal respiration (Vmax) up to 40%. A similar LMF-induced increase in Vmax was also observed in mitochondria isolated from rat hearts subjected to ischemia-reperfusion (I-R) injury. We then obtained data showing that LMF- mediated bell-shaped response was also observed in the activity of several enzymes involved in oxidative phosphorylation (OXPHOS), including Complexes II, III, and V, and citrate synthase. By contrast, similar LMF caused little change in the enzymatic activity of Complex I. Interestingly, mROS generation responded to LMF with an inverted bell-shaped decrease. We propose a radical pair mechanism of magnetoreception in cytochromes, catalytical reactions, and iron-sulfur clusters within the OXPHOS enzymes to explain how an LMF can increase the likelihood of electron spin transitions from singlet to triplet state and reverse it as the magnetic field strength further increases, resulting in a bell-shaped response. Our results indicate that a narrow range of LMF can enhance mitochondrial bioenergetics and decrease mROS. This may provide a non-invasive approach to treating diseases, such as I-R injury, when energy generation is compromised and oxidative stress is magnified.

biophysics↗

bioRxiv2021

iPSC modeling shows uncompensated mitochondrial mediated oxidative stress underlies early heart failure in hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart defect with 30% mortality from heart failure (HF) in the first year of life, but why only some patients suffer early-HF and its cause remain unknown. Modeling using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) showed early-HF patient iPSC-CM have increased apoptosis, redox stress, and failed antioxidant response. This was associated with mitochondrial permeability transition pore (mPTP) opening, mitochondrial hyperfusion and respiration defects. Whereas iPSC-CM from patients without early-HF had hyper-elevated antioxidant response with increased mitochondrial fission and mitophagy. Single cell transcriptomics showed dichotomization by HF outcome, with mitochondrial dysfunction and endoplasmic reticulum (ER) stress associated with early-HF. Importantly, oxidative stress and apoptosis associated with early HF were rescued by sildenafil inhibition of mPTP opening or TUDCA suppression of ER stress. Together these findings demonstrate a new paradigm for modeling clinical outcome in iPSC-CM, demonstrating uncompensated mitochondrial oxidative stress underlies early HF in HLHS.

cell biology↗

bioRxiv2019

Inhibition of the mitochondrial permeability transition exerts sex-specific stimulatory effect on fracture repair

Bone fracture is accompanied by mechanical stresses and inflammation - conditions that impair mitochondria via the phenomenon of permeability transition. This phenomenon occurs due to opening of the mitochondrial permeability transition pore (MPTP) promoted by cyclophilin D (CypD). MPTP opening exacerbates inflammation and cell death and, thus can disrupt fracture repair. Here we tested a hypothesis that protecting mitochondria from MPTP opening via inhibition of CypD improves fracture repair. Our data indicate that osteoblast activity, bone formation, and biomechanical properties of repaired bones were significantly increased in CypD knock-out mice when compared to controls during fracture repair. These effects were observed in male but not female mice, thus showing sexual dimorphism. Pharmacological inhibition of CypD with NIM811 in male mice also stimulated fracture repair. In addition, CypD knock-out or pharmacological inhibition produced pro-osteogenic effect in isolated bone marrow osteoprogenitors. This in vitro effect was associated with higher mitochondrial respiration and increased {beta}-catenin activity regulated by mitochondria-dependent acetylation. Our findings implicate a sex-specific role of MPTP in bone fracture and suggest CypD inhibition as a modality to promote fracture repair.

biochemistry↗