Decoding Organelle Interactions: Unveiling Molecular Mechanisms and Disease Therapies.

Organelles, substructures in the cytoplasm with specific morphological structures and functions, interact with each other via membrane fusion, membrane transport, and protein interactions, collectively termed organelle interaction. Organelle interaction is a complex biological process involving the interaction and regulation of several organelles, including the interaction between mitochondria-endoplasmic reticulum, endoplasmic reticulum-Golgi, mitochondria-lysosomes, and endoplasmic reticulum-peroxisomes. This interaction enables intracellular substance transport, metabolism, and signal transmission, and is closely related to the occurrence, development, and treatment of many diseases, such as cancer, neurodegenerative diseases, and metabolic diseases. Herein, the mechanisms and regulation of organelle interactions are reviewed, which are critical for understanding basic principles of cell biology and disease development mechanisms. The findings will help to facilitate the development of novel strategies for disease prevention, diagnosis, and treatment opportunities.

Low-dose Olaparib improves septic cardiac function by reducing ferroptosis via accelerated mitophagy flux.

Sepsis is a dysregulated response to infection that can result in life-threatening organ failure, and septic cardiomyopathy is a serious complication involving ferroptosis. Olaparib, a classic targeted drug used in oncology, has demonstrated potential protective effects against sepsis. However, the exact mechanisms underlying its action remain to be elucidated. In our study, we meticulously screened ferroptosis genes associated with sepsis, and conducted comprehensive functional enrichment analyses to delineate the relationship between ferroptosis and mitochondrial damage. Eight sepsis-characterized ferroptosis genes were identified in sepsis patients, including DPP4, LPIN1, PGD, HP, MAPK14, POR, GCLM, and SLC38A1, which were significantly correlated with mitochondrial quality imbalance. Utilizing DrugBank and molecular docking, we demonstrated a robust interaction of Olaparib with these genes. Lipopolysaccharide (LPS)-stimulated HL-1 cells and monocytes were used to establish an in vitro sepsis model. Additionally, an in vivo model was developed using mice subjected to cecal ligation and perforation (CLP). Intriguingly, low-dose Olaparib (5 mg/kg) effectively targeted and mitigated markers associated with ferroptosis, concurrently improving mitochondrial quality. This led to a marked enhancement in cardiac function and a significant increase in survival rates in septic mice (p < 0.05). The mechanism through which Olaparib ameliorates ferroptosis in cardiac and leukocyte cells post-sepsis is attributed to its facilitation of mitophagy, thus favoring mitochondrial integrity. In conclusion, our findings suggest that low-dose Olaparib can improve mitochondrial quality by accelerating mitophagy flux, consequently inhibiting ferroptosis and preserving cardiac function after sepsis.

Activated Drp1 regulates p62-mediated autophagic flux and aggravates inflammation in cerebral ischemia-reperfusion via the ROS-RIP1/RIP3-exosome axis.

BACKGROUND: Cerebral ischemia-reperfusion injury (CIRI) refers to a secondary brain injury that can occur when the blood supply to the ischemic brain tissue is restored. However, the mechanism underlying such injury remains elusive. METHODS: The 150 male C57 mice underwent middle cerebral artery occlusion (MCAO) for 1 h and reperfusion for 24 h, Among them, 50 MCAO mice were further treated with Mitochondrial division inhibitor 1 (Mdivi-1) and 50 MCAO mice were further treated with N-acetylcysteine (NAC). SH-SY5Y cells were cultured in a low-glucose culture medium for 4 h under hypoxic conditions and then transferred to normal conditions for 12 h. Then, cerebral blood flow, mitochondrial structure, mitochondrial DNA (mtDNA) copy number, intracellular and mitochondrial reactive oxygen species (ROS), autophagic flux, aggresome and exosome expression profiles, cardiac tissue structure, mitochondrial length and cristae density, mtDNA and ROS content, as well as the expression of Drp1-Ser616/Drp1, RIP1/RIP3, LC3 II/LC3 I, TNF-α, IL-1ß, etc., were detected under normal or Drp1 interference conditions. RESULTS: The mtDNA content, ROS levels, and Drp1-Ser616/Drp1 were elevated by 2.2, 1.7 and 2.7 times after CIRI (P < 0.05). However, the high cytoplasmic LC3 II/I ratio and increased aggregation of p62 could be reversed by 44% and 88% by Drp1 short hairpin RNA (shRNA) (P < 0.05). The low fluorescence intensity of autophagic flux and the increased phosphorylation of RIP3 induced by CIRI could be attenuated by ROS scavenger, NAC (P < 0.05). RIP1/RIP3 inhibitor Necrostatin-1 (Nec-1) restored 75% to a low LC3 II/LC3 I ratio and enhanced 2 times to a high RFP-LC3 after Drp1 activation (P < 0.05). In addition, although CIRI-induced ROS production caused no considerable accumulation of autophagosomes (P > 0.05), it increased the packaging and extracellular secretion of exosomes containing p62 by 4 - 5 times, which could be decreased by Mdivi-1, Drp1 shRNA, and Nec-1 (P < 0.05). Furthermore, TNF-α and IL-1ß increased in CIRI-derived exosomes could increase RIP3 phosphorylation in normal or oxygen-glucose deprivation/reoxygenation (OGD/R) conditions (P < 0.05). CONCLUSIONS: CIRI activated Drp1 and accelerated the p62-mediated formation of autophagosomes while inhibiting the transition of autophagosomes to autolysosomes via the RIP1/RIP3 pathway activation. Undegraded autophagosomes were secreted extracellularly in the form of exosomes, leading to inflammatory cascades that further damaged mitochondria, resulting in excessive ROS generation and the blockage of autophagosome degradation, triggering a vicious cycle.