Hypoxia-induced mitochondrial stress granules

Protein aggregation and biomolecular condensation in hypoxic environments (Review)

Due to molecular forces, biomacromolecules assemble into liquid condensates or solid aggregates, and their corresponding formation and dissolution processes are controlled. Protein homeostasis is disrupted by increasing age or environmental stress, leading to irreversible protein aggregation. Hypoxic pressure is an important factor in this process, and uncontrolled protein aggregation has been widely observed in hypoxia‑related conditions such as neurodegenerative disease, cardiovascular disease, hypoxic brain injury and cancer. Biomolecular condensates are also high‑order complexes assembled from macromolecules. Although they exist in different phase from protein aggregates, they are in dynamic balance under certain conditions, and their activation or assembly are considered as important regulatory processes in cell survival with hypoxic pressure. Therefore, a better understanding of the relationship between hypoxic stress, protein aggregation and biomolecular condensation will bring marked benefits in the clinical treatment of various diseases. The aim of the present review was to summarize the underlying mechanisms of aggregate assembly and dissolution induced by hypoxic conditions, and address recent breakthroughs in understanding the role of aggregates in hypoxic‑related diseases, given the hypotheses that hypoxia induces macromolecular assemblage changes from a liquid to a solid phase, and that adenosine triphosphate depletion and ATP‑driven inactivation of multiple protein chaperones play important roles among the process. Moreover, it is anticipated that an improved understanding of the adaptation in hypoxic environments could extend the overall survival of patients and provide new strategies for hypoxic‑related diseases.

Mitochondrial p38 Mitogen-Activated Protein Kinase: Insights into Its Regulation of and Role in LONP1-Deficient Nematodes

p38 Mitogen-Activated Protein Kinase (MAPK) cascades are central regulators of numerous physiological cellular processes, including stress response signaling. In C. elegans, mitochondrial dysfunction activates a PMK-3/p38 MAPK signaling pathway (MAPKmt), but its functional role still remains elusive. Here, we demonstrate the induction of MAPKmt in worms deficient in the lonp-1 gene, which encodes the worm ortholog of mammalian mitochondrial LonP1. This induction is subjected to negative regulation by the ATFS-1 transcription factor through the CREB-binding protein (CBP) ortholog CBP-3, indicating an interplay between both activated MAPKmt and mitochondrial Unfolded Protein Response (UPRmt) surveillance pathways. Our results also reveal a genetic interaction in lonp-1 mutants between PMK-3 kinase and the ZIP-2 transcription factor. ZIP-2 has an established role in innate immunity but can also modulate the lifespan by maintaining mitochondrial homeostasis during ageing. We show that in lonp-1 animals, ZIP-2 is activated in a PMK-3-dependent manner but does not confer increased survival to pathogenic bacteria. However, deletion of zip-2 or pmk-3 shortens the lifespan of lonp-1 mutants, suggesting a possible crosstalk under conditions of mitochondrial perturbation that influences the ageing process. Furthermore, loss of pmk-3 specifically diminished the extreme heat tolerance of lonp-1 worms, highlighting the crucial role of PMK-3 in the heat shock response upon mitochondrial LONP-1 inactivation.

Triethyl phosphine decorated cerium oxide nanoparticles exhibit selective killing of the unicellular protozoan parasite Leishmania donovani

Globally, Leishmaniasis affects underprivileged communities of the nations and chemotherapy remains one of the preferred treatment options. However, the cytotoxicity, side effects, and cost of the present chemotherapies limit their utilization. Auranofin [an organogold compound having significant structural similarity with triethyl-phosphine (TEP)] has been reported as an effective therapy for Leishmaniasis treatment. Considering the high cost of gold and the strong affinity of cerium oxide nanoparticles (CeNPs) to phosphine ligands, we designed TEP-decorated CeNPs (CeNPs-TEP) and used them as a novel antileishmanial agent. The hydrodynamic size of synthesized CeNPs and CeNPs-TEP was observed to be 22.2 ± 3.7 nm and 92.11 ± 6.2 nm, respectively. CeNPs-TEP provided aqueous stability to TEP as TEP alone is extremely unstable in water. Exposure of CeNPs-TEP showed ~ 60 and ~ 82% cell death in Leishmania donovani Ag83 promastigotes after 24 and 48 h, respectively. The same concentration of CeNPs-TEP did not affect the cellular viability of RAW 264.7 macrophage cells significantly. The oxidative stress and depolarization of the mitochondrial membrane were also observed after the treatment of CeNPs-TEP. Exposure of CeNPs-TEP induced a ~ 2.2-fold increase in ROS generation inside Leishmania donovani Ag83 cells. Dual staining with ethidium bromide and acridine orange reveals that these processes ultimately result in cell death. The results conclude that a combination of CeNPs and TEP could open the door for developing novel antileishmanial therapeutics in the future.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03813-7.