Biology subjects

Onukwufor, J. O.

Publications and source records attributed to Onukwufor, J. O..

3 recordsLinked to original sources

bioRxiv2024

DMT1 knockout abolishes ferroptosis induced mitochondrial dysfunction in C. elegans amyloid beta proteotoxicity

Iron is critical for neuronal activity and metabolism, and iron dysregulation alters these functions in age-related neurodegenerative disorders, such as Alzheimers disease (AD). AD is a chronic neurodegenerative disease characterized by progressive neuronal dysfunction, memory loss and decreased cognitive function. AD patients exhibit elevated iron levels in the brain compared to age-matched non-AD individuals. However, the degree to which iron overload contributes to AD pathogenesis is unclear. Here, we evaluated the involvement of ferroptosis, an iron-dependent cell death process, in mediating AD-like pathologies in C. elegans. Results showed that iron accumulation occurred prior to the loss of neuronal function as worms age. In addition, energetic imbalance was an early event in iron-induced loss of neuronal function. Furthermore, the loss of neuronal function was, in part, due to increased mitochondrial reactive oxygen species mediated oxidative damage, ultimately resulting in ferroptotic cell death. The mitochondrial redox environment and ferroptosis were modulated by pharmacologic processes that exacerbate or abolish iron accumulation both in wild-type worms and worms with increased levels of neuronal amyloid beta (A{beta}). However, neuronal A{beta} worms were more sensitive to ferroptosis-mediated neuronal loss, and this increased toxicity was ameliorated by limiting the uptake of ferrous iron through knockout of divalent metal transporter 1 (DMT1). In addition, DMT1 knockout completely suppressed phenotypic measures of A{beta} toxicity with age. Overall, our findings suggest that iron-induced ferroptosis alters the mitochondrial redox environment to drive oxidative damage when neuronal A{beta} is overexpressed. DMT1 knockout abolishes neuronal A{beta}-associated pathologies by reducing neuronal iron uptake. HighlightsO_LIEnergetic imbalance is an early event in iron-induced loss of neuronal function C_LIO_LINeuronal A{beta} increases susceptibility to ferroptosis mediated oxidative damage C_LIO_LIDivalent metal transporter 1 knockout protects against iron-induced oxidative damage and ferroptosis C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=196 HEIGHT=200 SRC="FIGDIR/small/607074v1_ufig1.gif" ALT="Figure 1"> View larger version (55K): org.highwire.dtl.DTLVardef@927aaorg.highwire.dtl.DTLVardef@10b121forg.highwire.dtl.DTLVardef@1d2d6aforg.highwire.dtl.DTLVardef@10cb797_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2024

Interactive effects of temperature, cadmium, and hypoxia on rainbow trout (Oncorhynchus mykiss) liver mitochondrial bioenergetics

Fish in their natural environments possess elaborate mechanisms that regulate physiological function to mitigate the adverse effects of multiple environmental stressors such as temperature, metals, and hypoxia. We investigated how warm acclimation affects mitochondrial responses to Cd, hypoxia, and acute temperature shifts (heat shock and cold snap) in rainbow trout. We observed that state 3 respiration driven by complex I (CI) was resistant to the stressors while warm acclimation and Cd reduced complex I +II (CI + II) driven state 3 respiration. In contrast, state 4 (leak) respirations for both CI and CI + II were consistently stimulated by warm acclimation resulting in reduced mitochondrial coupling efficiency (respiratory control ratio, RCR). Warm acclimation and Cd exacerbated their individual effect on leak respiration to further reduce the RCR. Moreover, the effect of warm acclimation on mitochondrial bioenergetics aligned with its inhibitory effect on activities of citrate synthase and both CI and CII. Unlike the Cd and warm acclimation combined exposure, hypoxia alone and in combination with warm acclimation and/or Cd abolished the stimulation of CI and CI + II powered leak respirations resulting in partial recovery of RCR. The response to acute temperature shifts indicated that while state 3 respiration returned to pre-acclimation level, the leak respiration did not. Overall, our findings suggest a complex in vivo interaction of multiple stressors on mitochondrial function that are not adequately predicted by their individual effects. HighlightsO_LIMitochondrial bioenergetics plasticity was investigated. C_LIO_LIStimulation of mitochondrial leak state is a key effect of warm acclimation. C_LIO_LIState 3 but not leak respiration returns to control status after warm acclimation. C_LIO_LIWarm acclimation and Cd additively stimulate leak respiration and reduce RCR. C_LIO_LIHypoxia protects against deleterious effects of warm acclimation and Cd exposure. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=71 SRC="FIGDIR/small/603625v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@1d0c9b2org.highwire.dtl.DTLVardef@6a0398org.highwire.dtl.DTLVardef@122ef1org.highwire.dtl.DTLVardef@1c7f427_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2019

Quantification of reactive oxygen species production by the red fluorescent proteins KillerRed, SuperNova and mCherry.

Fluorescent proteins can generate reactive oxygen species (ROS) upon absorption of photons via type I and II photosensitization mechanisms. The red fluorescent proteins KillerRed and SuperNova are phototoxic proteins engineered to generate ROS and are used in a variety of biological applications. However, their relative quantum yields and rates of ROS production are unclear, which has limited the interpretation of their effects when used in biological systems. We cloned and purified KillerRed, SuperNova, and mCherry - a related red fluorescent protein not typically considered a photosensitizer - and measured the superoxide (O2 *-) and singlet oxygen (1O2) quantum yields with irradiation at 561 nm. The formation of the O2 *--specific product 2-hydroxyethidium (2-OHE+) was quantified via HPLC separation with fluorescence detection. Relative to a reference photosensitizer, Rose Bengal, the O2 *- quantum yield ({Phi}O2 *-) of SuperNova was determined to be 0.00150, KillerRed was 0.00097, and mCherry 0.00120. At an excitation fluence of 916.5 J/cm2 and matched absorption at 561 nm, SuperNova, KillerRed and mCherry made 3.81, 2.38 and 1.65 M O2 *-/min, respectively. Using the probe Singlet Oxygen Sensor Green (SOSG), we ascertained the 1O2 quantum yield ({Phi}1O2) for SuperNova to be 0.0220, KillerRed 0.0076, and mCherry 0.0057. These photosensitization characteristics of SuperNova, KillerRed and mCherry improve our understanding of fluorescent proteins and are pertinent for refining their use as tools to advance our knowledge of redox biology.\n\nGRAPHICAL ABSTRACT\n\nO_FIG O_LINKSMALLFIG WIDTH=183 HEIGHT=200 SRC=\"FIGDIR/small/777417v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (20K):\norg.highwire.dtl.DTLVardef@197ad04org.highwire.dtl.DTLVardef@dffa05org.highwire.dtl.DTLVardef@9765e4org.highwire.dtl.DTLVardef@1a26545_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗