Mitochondrial reverse electron transport (RET) represents a fundamental but potentially hazardous metabolic process in eukaryotic cells. This review systematically examines current understanding of RET mechanisms and their pathophysiological consequences. RET occurs when electrons flow inversely from reduced coenzyme Q (CoQH₂) to complex I, driven by excessive reduction of the CoQ pool and elevated mitochondrial membrane potential, resulting in substantial superoxide production. While moderate RET contributes to physiological redox signaling, sustained RET activation leads to oxidative damage and activates regulated cell death pathways. Notably, RET demonstrates metabolic duality: it facilitates ATP generation through NAD⁺ reduction while simultaneously inducing mitochondrial dysfunction via reactive oxygen species overproduction. Pathologically, RET has been implicated in myocardial ischemia–reperfusion injury, neurodegenerative disorders including Alzheimer’s diseases, and exhibits context-dependent roles in tumor progression. Emerging evidence also suggests RET involvement in microbial pathogenesis through modulation of host immune responses. These findings position RET as a critical regulatory node in cellular metabolism with broad implications for human diseases. Future investigations should focus on developing tissue-specific RET modulators and elucidating the molecular switches governing its activation threshold, which may yield novel therapeutic strategies for diverse pathological conditions.

Radiotherapy (RT) is one of the most effective cancer treatments. However, successful radiation protection for normal tissue is a clinical challenge. Our previous study observed that MitoQ, a mitochondria-targeted antioxidant, was adsorbed to the inner mitochondrial membrane and remained the cationic moiety in the intermembrane space. The positive charges in MitoQ restrained the activity of respiratory chain complexes and decreased proton production. Therefore, a pseudo-mitochondrial membrane potential (PMMP) was developed via maintenance of exogenous positive charges. This study identified that PMMP constructed by MitoQ could effectively inhibit mitochondrial respiration within normal cells, disrupt energy metabolism, and activate adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) signaling to induce autophagy. As such, it could not lead to starvation-induced autophagy among tumor cells due to the different energy phenotypes between normal and tumor cells (normal cells depend on mitochondrial respiration for energy supply, while tumor cells rely on aerobic glycolysis). Therefore, we successfully protected the normal cells from radiation-induced damage without affecting the tumor-killing efficacy of radiation by utilizing selective autophagy. MitoQ-constructed PMMP provides a new therapeutic strategy for specific radiation protection.

14-O-[(4,6-Diaminopyrimidine-2-yl)thioacetyl] mutilin (DPTM), a novel pleuromutilin candidate with a substituted pyrimidine moiety, has been confirmed to possess excellent antibacterial activity against Gram-positive bacteria. To illustrate the pharmacokinetic profile after intravenous (i.v.), intramuscular (i.m.) and oral (p.o.) administrations with DPTM, as well as tissue distribution and excretion via urine and feces in vivo, a specific, sensitive and robust HPLC-MS/MS method was first developed to determine DPTM in rat plasma, various tissues, urine and feces. The plasma, tissues, urine and feces samples were treated by protein precipitation with acetonitrile using tiamulin fumarate as an internal standard (IS). This method which was achieved on an HPLC system detector equipped with an ESI interface, was sensitive with 5 ng/mL as the lower limit of detection and exhibited good linearity (R² > 0.9900) in the range of 5–4000 ng/mL for plasma, various tissues, urine and feces, as well as intra-day precision, inter-day precision and accuracy. The matrix effects ranged from 94.2 to 109.7% with RSD ≤ 9.4% and the mean extraction recoveries ranged from 95.4 to 109.5% in plasma, tissue homogenates, urine and feces (RSD ≤ 9.9). After i.v., i.m. and p.o. administrations, DPTM was rapidly absorbed and metabolized in rats with the half-life (t_1/2) of 1.70–1.86, 3.23–3.49 and 4.38–4.70 for 10, 25 and 75 mg/kg doses, respectively. The tissue distribution showed that DPTM was diffused into all the tested tissues, especially into the intestine and lung. Excretion via urine and feces studies demonstrated that DPTM was mainly excreted by feces after administration.

Ionizing radiation like X-rays or heavy ions can induce cellular oxidative stress and damage due to the production of reactive oxygen species. The TrxR/Trx system has a considerable impact on maintaining body redox homeostasis and against cell oxidative damage. In this paper, we described the potential of one natural small molecule, Honokiol (HKL), to repair radiation damage in vivo and in vitro. Pretreatment with HKL significantly protected cell viability and decreased cellular damage, as confirmed by the results of MTT assay, colony formation assay, micronucleus test, and γ-H2AX immunofluorescence analysis. Western blot experiments showed that HKL could mediate the oxidative imbalance of the TrxR/Trx system induced by ionizing radiation. The protective effect of HKL might be associated with regulating the TrxR/Trx system, evidenced by silencing TrxR expression with shRNA. Additional co-culture assays provided evidence that the HKL-precondition might attenuate the ionizing radiation-induced bystander effect. In vivo, studies showed that HKL would improve action against the lung cell tissue of the irradiated mice and prolong mouse survival. The findings indicated that HKL is a potential radioprotective agent that preserves the redox homeostasis of the TrxR/Trx system. Overall, the findings presented here demonstrate that HKL has the potential to be a novel radioprotector capable of cellular protection against radiation-induced injuries. These discoveries hold critical significance for both cancer radiotherapeutics and space radiation protection protocols.