Elevating bioavailable iron levels in mitochondria suppresses the defective phenotypes caused by PINK1 loss-of-function in Drosophila melanogaster

Phenolamides from Rootstocks of Lycium ruthenicum Murr by Ligand Fishing and Their Neuroprotective Effects

Lycium ruthenicum Murr is an important edible and medicinal plant widely cultivated in Northwest China. Our previous study found that its fruit possessed rich polyphenols exhibiting significant neuroprotective effects, inspiring us to investigate the active constituents of its rootstocks, which have never been reported. In this study, we rapidly identified four phenolamides (1-4) possessing monoamine oxidase B (MAO-B) inhibitory effect by using MAO-B-functionalized cellulose filter paper-based ligand fishing, and their structures were elucidated with NMR and MS. Compounds 1, 2, and 4 exhibited moderate inhibitory effect on MAO-B with IC50 values of 71.44 ± 1.81, 28.97 ± 1.20, and 25.58 ± 0.74 μM, respectively, and enzyme kinetic analysis, molecular docking, and molecular dynamics further revealed the inhibition mechanism. All four phenolamides displayed a neuroprotective effect against 1-methyl-4-phenylpyridinium -induced SH-SY5Y cells model, among which 2 and 4 significantly reduced intracellular MAO-B activity and improved the ATP content. Western blot revealed that compounds 2 and 4 alleviated the oxidative stress through up-regulation of the expression of Nrf2 and HO-1 protein, promoting mitophagy via activating the PINK1/Parkin pathway. Moreover, compounds 2 and 4 extended the lifespan, dopamine and ATP levels, locomotor behavior, and olfactory ability of the PINK1B9 flies, a drosophila model of Parkinson's disease. Meanwhile, compounds 1-4 showed potent antioxidative activities on DPPH, ABTS+, and PTIO radical scavenging assays. These results revealed the health-promoting effects of the rootstocks in preventing and treating neurodegenerative diseases, laying the scientific foundation for the exploitation of this plant byproduct for the development of functional food formulations and pharmaceutical products.

Homeostasis and metabolism of iron and other metal ions in neurodegenerative diseases

As essential micronutrients, metal ions such as iron, manganese, copper, and zinc, are required for a wide range of physiological processes in the brain. However, an imbalance in metal ions, whether excessive or insufficient, is detrimental and can contribute to neuronal death through oxidative stress, ferroptosis, cuproptosis, cell senescence, or neuroinflammation. These processes have been found to be involved in the pathological mechanisms of neurodegenerative diseases. In this review, the research history and milestone events of studying metal ions, including iron, manganese, copper, and zinc in neurodegenerative diseases such as Parkinson's disease (PD), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD), will be introduced. Then, the upstream regulators, downstream effector, and crosstalk of mental ions under both physiologic and pathologic conditions will be summarized. Finally, the therapeutic effects of metal ion chelators, such as clioquinol, quercetin, curcumin, coumarin, and their derivatives for the treatment of neurodegenerative diseases will be discussed. Additionally, the promising results and limitations observed in clinical trials of these metal ion chelators will also be addressed. This review will not only provide a comprehensive understanding of the role of metal ions in disease development but also offer perspectives on their modulation for the prevention or treatment of neurodegenerative diseases.

Iron-sulfur cluster loss in mitochondrial CISD1 mediates PINK1 loss-of-function phenotypes

Parkinson's disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra of the midbrain. Familial cases of PD are often caused by mutations of PTEN-induced kinase 1 (PINK1) and the ubiquitin ligase Parkin, both pivotal in maintaining mitochondrial quality control. CISD1, a homodimeric mitochondrial iron-sulfur-binding protein, is a major target of Parkin-mediated ubiquitination. We here discovered a heightened propensity of CISD1 to form dimers in Pink1 mutant flies and in dopaminergic neurons from PINK1 mutation patients. The dimer consists of two monomers that are covalently linked by a disulfide bridge. In this conformation CISD1 cannot coordinate the iron-sulfur cofactor. Overexpressing Cisd, the Drosophila ortholog of CISD1, and a mutant Cisd incapable of binding the iron-sulfur cluster in Drosophila reduced climbing ability and lifespan. This was more pronounced with mutant Cisd and aggravated in Pink1 mutant flies. Complete loss of Cisd, in contrast, rescued all detrimental effects of Pink1 mutation on climbing ability, wing posture, dopamine levels, lifespan, and mitochondrial ultrastructure. Our results suggest that Cisd, probably iron-depleted Cisd, operates downstream of Pink1 shedding light on PD pathophysiology and implicating CISD1 as a potential therapeutic target.

Mitochondrial Differentiation during Spermatogenesis: Lessons from Drosophila melanogaster

Numerous diseases can arise as a consequence of mitochondrial malfunction. Hence, there is a significant focus on studying the role of mitochondria in cancer, ageing, neurodegenerative diseases, and the field of developmental biology. Mitochondria could exist as discrete organelles in the cell; however, they have the ability to fuse, resulting in the formation of interconnected reticular structures. The dynamic changes between these forms correlate with mitochondrial function and mitochondrial health, and consequently, there is a significant scientific interest in uncovering the specific molecular constituents that govern these transitions. Moreover, the specialized mitochondria display a wide array of variable morphologies in their cristae formations. These inner mitochondrial structures are closely associated with the specific functions performed by the mitochondria. In multiple cases, the presence of mitochondrial dysfunction has been linked to male sterility, as it has been observed to cause a range of abnormal spermatogenesis and sperm phenotypes in different species. This review aims to elucidate the dynamic alterations and functions of mitochondria in germ cell development during the spermatogenesis of Drosophila melanogaster.

Mitochondrial iron dyshomeostasis and its potential as a therapeutic target for Parkinson's disease

Abnormal iron accumulation has been implicated in the etiology of Parkinson's disease (PD). Understanding how iron damages dopaminergic neurons in the substantia nigra (SN) of PD is particularly important for developing targeted neurotherapeutic strategies for the disease. However, it is still not fully understood how excess iron contributes to the neurodegeneration of dopaminergic neurons in PD. There has been increased attention on mitochondrial iron dyshomeostasis, iron-induced mitochondrial dysfunction and ferroptosis in PD. Therefore, this review begins with a brief introduction to describe cellular iron metabolism and the dysregulation of iron metabolism in PD. Then we provide an update on how iron is delivered to mitochondria and induces the damage of dopaminergic neurons in PD. In addition, we also summarize new research progress on iron-dependent ferroptosis in PD and mitochondria-localized proteins involved in ferroptosis. This will provide new insight into potential therapeutic strategies targeting mitochondrial iron dysfunction.

Polyphenolic glycosides with unusual four-membered ring possessing anti-Parkinson's disease potential from black wolfberry

This work reports the isolation of seven undescribed polyphenolic glycosides (1-7) together with fourteen known compounds (8-21) from the fruit of Lycium ruthenicum Murray. The structures of the undescribed compounds were identified based on comprehensive spectroscopic methods including IR, HRESIMS, NMR and ECD, and chemical hydrolysis. Compounds 1-3 possess an unusual four-membered ring, while 11-15 were firstly isolated from this fruit. Interestingly, compounds 1-3 inhibited monoamine oxidase B with IC₅₀ of 25.36 ± 0.44, 35.36 ± 0.54, and 25.12 ± 1.59 μM, respectively, and showed significant neuroprotective effect on PC12 cells injured by 6-OHDA. Moreover, compound 1 improved the lifespan, dopamine level, climbing behaviour, and olfactory ability of the PINK1^B9 flies, a Drosophila model of Parkinson's disease. This work presents the first in vivo neuroprotective evidence of the small molecular compounds in L. ruthenicum Murray fruit, indicating its good potential as neuroprotectant.

Iron Homeostasis in Insects

Iron is an essential micronutrient for all types of organisms; however, iron has chemical properties that can be harmful to cells. Because iron is both necessary and potentially damaging, insects have homeostatic processes that control the redox state, quantity, and location of iron in the body. These processes include uptake of iron from the diet, intracellular and extracellular iron transport, and iron storage. Early studies of iron-binding proteins in insects suggested that insects and mammals have surprisingly different mechanisms of iron homeostasis, including different primary mechanisms for exporting iron from cells and for transporting iron from one cell to another, and subsequent studies have continued to support this view. This review summarizes current knowledge about iron homeostasis in insects, compares insect and mammalian iron homeostasis mechanisms, and calls attention to key remaining knowledge gaps.

M2 Macrophage-Derived Exosomal Ferritin Heavy Chain Promotes Colon Cancer Cell Proliferation

Colon cancer is a widespread life-threatening malignancy with complex and multifactorial etiology. Both epidemiological cohort studies and basic research support the substantial role of iron metabolism in colon cancer. Thus, understanding the mechanisms of how essential iron metabolic proteins are dysregulated may provide new treatment strategies for colon cancer. Ferritin is the main iron storage protein that occupies a vital position in iron metabolism. Studies reported that ferritin is differentially highly expressed in tissues from multiple malignancies. However, the source and function of highly expressed ferritin in colon cancer have not been explored. In this study, we found that the protein level but not RNA level of ferritin heavy chain (FTH1) was upregulated in colon cancer using paired clinical samples. Co-culture system was used to mimic the in vivo circumstance and study the cell-cell communication of macrophages and colon cancer cells. Results showed that M2 macrophages could substantially increase the FTH1 levels in colon cancer cells. This effect could be blocked by the exosome biogenesis/ secretion inhibitor GW4869, implying the vital role of exosomes in this biological process. Besides, we found that purified exosomes from M2 macrophages could deliver FTH1 into colon cancer cells and promote cell proliferation. Furtherly, EdU assay and live cell imaging system were performed in FTH1-OE (overexpression) colon cancer cell lines and confirmed the cell proliferation promoting effect of FTH1. Our results unveil the source and function of highly expressed FTH1 in colon cancer and provide a new potential therapeutic target for the treatment of colon cancer.

Mitoferrin, Cellular and Mitochondrial Iron Homeostasis

Iron is essential for many cellular processes, but cellular iron homeostasis must be maintained to ensure the balance of cellular signaling processes and prevent disease. Iron transport in and out of the cell and cellular organelles is crucial in this regard. The transport of iron into the mitochondria is particularly important, as heme and the majority of iron-sulfur clusters are synthesized in this organelle. Iron is also required for the production of mitochondrial complexes that contain these iron-sulfur clusters and heme. As the principal iron importers in the mitochondria of human cells, the mitoferrins have emerged as critical regulators of cytosolic and mitochondrial iron homeostasis. Here, we review the discovery and structure of the mitoferrins, as well as the significance of these proteins in maintaining cytosolic and mitochondrial iron homeostasis for the prevention of cancer and many other diseases.

Ferrostatin-1 alleviated TNBS induced colitis via the inhibition of ferroptosis

Inflammatory bowel disease (IBD), consisting of ulcerative colitis (UC) and Crohn's disease (CD), is a chronic relapsing and life-threatening inflammatory disorder that mainly affect the intestinal tract. The mainstream therapies for moderate to severe IBD lie in the use of immunosuppressive agents. However, it encountered the problem of drug tolerance and significant adverse events. Therefore, identifying novel signal pathways involved in IBD is necessary to satisfy the unmet treatment needs of IBD patients. There existed some hints between iron and IBD, and was reported that ferroptosis induced in UC. However, as another important subtype of IBD, whether ferroptosis also occurred in CD remains unclear. In this study, we found that the dysregulation of iron, lipid peroxidation and redox homeostasis were involved in CD; the administration of ferroptosis inhibitor Ferrostatin-1 could alleviate pathological phenotypes of TNBS induced CD-like colitis in mice. Our results provide a new hopeful therapeutic strategy in treating CD, especially for those who suffered from the tolerance of existing immunosuppressive agent drugs.

Lipocalin 2 regulates iron homeostasis, neuroinflammation, and insulin resistance in the brains of patients with dementia: Evidence from the current literature

Dementia accompanied by memory loss is considered one of the most common neurodegenerative diseases worldwide, and its prevalence is gradually increasing. Known risk factors for dementia include genetic background, certain lifestyle and dietary patterns, smoking, iron overload, insulin resistance, and impaired glucose metabolism in the brain. Here, we review recent evidence on the regulatory role of lipocalin 2 (LCN2) in dementia from various perspectives. LCN2 is a neutrophil gelatinase-associated protein that influences diverse cellular processes, including the immune system, iron homeostasis, lipid metabolism, and inflammatory responses. Although its functions within the peripheral system are most widely recognized, recent findings have revealed links between LCN2 and central nervous system diseases, as well as novel roles for LCN2 in neurons and glia. Furthermore, LCN2 may modulate diverse pathological mechanisms involved in dementia. Taken together, LCN2 is a promising therapeutic target with which to address the neuropathology of dementia.

The Importance of Drosophila melanogaster Research to UnCover Cellular Pathways Underlying Parkinson's Disease

Parkinson's disease (PD) is a complex neurodegenerative disorder that is currently incurable. As a consequence of an incomplete understanding of the etiology of the disease, therapeutic strategies mainly focus on symptomatic treatment. Even though the majority of PD cases remain idiopathic (~90%), several genes have been identified to be causative for PD, facilitating the generation of animal models that are a good alternative to study disease pathways and to increase our understanding of the underlying mechanisms of PD. Drosophila melanogaster has proven to be an excellent model in these studies. In this review, we will discuss the different PD models in flies and key findings identified in flies in different affected pathways in PD. Several molecular changes have been identified, of which mitochondrial dysfunction and a defective endo-lysosomal pathway emerge to be the most relevant for PD pathogenesis. Studies in flies have significantly contributed to our knowledge of how disease genes affect and interact in these pathways enabling a better understanding of the disease etiology and providing possible therapeutic targets for the treatment of PD, some of which have already resulted in clinical trials.

Human Dopaminergic Neurons Lacking PINK1 Exhibit Disrupted Dopamine Metabolism Related to Vitamin B6 Co-Factors

PINK1 loss-of-function mutations cause early onset Parkinson disease. PINK1-Parkin mediated mitophagy has been well studied, but the relevance of the endogenous process in the brain is debated.

Here, the absence of PINK1 in human dopaminergic neurons inhibits ionophore-induced mitophagy and reduces mitochondrial membrane potential. Compensatory, mitochondrial renewal maintains mitochondrial morphology and protects the respiratory chain. This is paralleled by metabolic changes, including inhibition of the TCA cycle enzyme mAconitase, accumulation of NAD⁺, and metabolite depletion. Loss of PINK1 disrupts dopamine metabolism by critically affecting its synthesis and uptake. The mechanism involves steering of key amino acids toward energy production rather than neurotransmitter metabolism and involves cofactors related to the vitamin B6 salvage pathway identified using unbiased multi-omics approaches.

We propose that reduction of mitochondrial membrane potential that cannot be controlled by PINK1 signaling initiates metabolic compensation that has neurometabolic consequences relevant to Parkinson disease.

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PINK1 KO hDANs do not undergo ionophore-induced mitophagy yet CI remains active

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PINK1 KO impacts the TCA cycle via mAconitase leading to depletion of key amino acids

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PINK1 KO silences PNPO, which provides essential biological co-factors

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Dopamine pools and neurotransmitter uptake are reduced by PINK1 loss of function

Systematic Surveys of Iron Homeostasis Mechanisms Reveal Ferritin Superfamily and Nucleotide Surveillance Regulation to be Modified by PINK1 Absence

Iron deprivation activates mitophagy and extends lifespan in nematodes. In patients suffering from Parkinson’s disease (PD), PINK1-PRKN mutations via deficient mitophagy trigger iron accumulation and reduce lifespan. To evaluate molecular effects of iron chelator drugs as a potential PD therapy, we assessed fibroblasts by global proteome profiles and targeted transcript analyses. In mouse cells, iron shortage decreased protein abundance for iron-binding nucleotide metabolism enzymes (prominently XDH and ferritin homolog RRM2). It also decreased the expression of factors with a role for nucleotide surveillance, which associate with iron-sulfur-clusters (ISC), and are important for growth and survival. This widespread effect included prominently Nthl1-Ppat-Bdh2, but also mitochondrial Glrx5-Nfu1-Bola1, cytosolic Aco1-Abce1-Tyw5, and nuclear Dna2-Elp3-Pold1-Prim2. Incidentally, upregulated Pink1-Prkn levels explained mitophagy induction, the downregulated expression of Slc25a28 suggested it to function in iron export. The impact of PINK1 mutations in mouse and patient cells was pronounced only after iron overload, causing hyperreactive expression of ribosomal surveillance factor Abce1 and of ferritin, despite ferritin translation being repressed by IRP1. This misregulation might be explained by the deficiency of the ISC-biogenesis factor GLRX5. Our systematic survey suggests mitochondrial ISC-biogenesis and post-transcriptional iron regulation to be important in the decision, whether organisms undergo PD pathogenesis or healthy aging.