The Ginsenoside Rg1 Rescues Mitochondrial Disorders in Aristolochic Acid-Induced Nephropathic Mice

Chronic exposure to aristolochic acid (AA) leads to renal interstitial fibrosis and nephropathy. In this study, we aimed to investigate the renoprotective effects of Panax ginseng extract (GE) and ginsenoside saponin (GS) on AA-induced nephropathy (AAN) in mice. Eighty female C3H/He mice were randomly divided into eight groups, including normal; AA (3 μg/mL for 56 days); AA with GE (125, 250, or 500 mg/kg/d for 14 days); and AA with important GE ingredients, Rg1, Rb1, or Rd (5 mg/kg/d for 14 days). Compared with the AA group, renal injuries were significantly decreased in the GE (250 mg/kg/d), Rb1, and Rg1 treatment groups. Rg1 exhibited the best renoprotection among all GS-treated groups. There were 24 peaks significantly altered among normal, AA, and AA + Rg1 groups, and four mitochondrial proteins were identified, including acyl-CoA synthetase medium-chain family member 2, upregulated during skeletal muscle growth 5 (Usmg5), mitochondrial aconitase 2 (ACO2), and cytochrome c oxidase subunit Va preprotein (COX5a). We demonstrated for the first time that the AAN mechanism and renoprotective effects of Rg1 are associated with expression of mitochondrial proteins, especially ACO2, Usmg5, and COX5a.

Dominant ACO2 mutations are a frequent cause of isolated optic atrophy

Biallelic mutations in ACO2, encoding the mitochondrial aconitase 2, have been identified in individuals with neurodegenerative syndromes, including infantile cerebellar retinal degeneration and recessive optic neuropathies (locus OPA9). By screening European cohorts of individuals with genetically unsolved inherited optic neuropathies, we identified 61 cases harboring variants in ACO2, among whom 50 carried dominant mutations, emphasizing for the first time the important contribution of ACO2 monoallelic pathogenic variants to dominant optic atrophy. Analysis of the ophthalmological and clinical data revealed that recessive cases are affected more severely than dominant cases, while not significantly earlier. In addition, 27% of the recessive cases and 11% of the dominant cases manifested with extraocular features in addition to optic atrophy. In silico analyses of ACO2 variants predicted their deleterious impacts on ACO2 biophysical properties. Skin derived fibroblasts from patients harboring dominant and recessive ACO2 mutations revealed a reduction of ACO2 abundance and enzymatic activity, and the impairment of the mitochondrial respiration using citrate and pyruvate as substrates, while the addition of other Krebs cycle intermediates restored a normal respiration, suggesting a possible short-cut adaptation of the tricarboxylic citric acid cycle. Analysis of the mitochondrial genome abundance disclosed a significant reduction of the mitochondrial DNA amount in all ACO2 fibroblasts. Overall, our data position ACO2 as the third most frequently mutated gene in autosomal inherited optic neuropathies, after OPA1 and WFS1, and emphasize the crucial involvement of the first steps of the Krebs cycle in the maintenance and survival of retinal ganglion cells. By screening European cohorts of individuals with genetically unsolved inherited optic neuropathies, Charif et al. report 61 new cases harboring variants in ACO2, among whom 50 with dominant mutations, emphasizing for the first time the important contribution of ACO2 monoallelic pathogenic variants to dominant optic atrophy.

TAMI-17. RELATIONSHIP BETWEEN IRON METABOLISM, IMMUNE CELL INFILTRATION AND SEX-BASED SURVIVAL DIFFERENCES IN GLIOMAS

Iron plays a central role in cellular metabolism, both in normal cellular functioning and in tumorigenesis. Recent evidence has shown sex-based survival differences in glioblastoma (GBM) may be related to differential expression of metabolism genes. We previously reported the iron regulating gene, HFE, was shown to have a sex-based survival impact in both low-grade gliomas and GBM. We additionally found that females with low HFE expressing tumors have significantly higher survival than males in GBM. To evaluate the relationship between iron gene expression and sex-based survival differences in GBM, we analyzed TCGA GBM gene expression and clinical data. We first analyzed the impact of iron genes on sex-based survival. In addition to HFE, FTL, TFRC, TF, and SLC39A8 (ZIP8), also showed sex-based survival differences. We then compared correlations of HFE and other iron genes to identify whether male and female GBMs differ in iron regulation and metabolism. HFE expression is significantly positively correlated with HMOX1, SLC25A28, SLC11A2, FTH1, HAMP, and TFR2 only in females. Alternatively, HFE expression is negatively correlated with ACO2 (mitochondrial aconitase) in males and ACO1 (cytoplasmic aconitase) in females. We noted that the expression of certain iron genes was highly associated with immune cell infiltration based on sex. TFR2, LRP1, and XIST expression were negatively correlated with low immune cell infiltration in females, but not males. Alternatively, in males, SLC11A2, ACO2, FOXO1, HIF1a, and HAMP genes were negatively correlated with immune infiltration. This suggests that differences in iron regulation between males and females may be contributing to differences in immune function and subsequent survival in GBM. These data suggest that the iron signature of a tumor reflects and possibly drives the metabolic and immune landscape of the tumor microenvironment thereby directly impacting survival differences between male and female GBMs.

SINEUP non-coding RNAs rescue defective frataxin expression and activity in a cellular model of Friedreich's Ataxia

Friedreich's ataxia (FRDA) is an untreatable disorder with neuro- and cardio-degenerative progression. This monogenic disease is caused by the hyper-expansion of naturally occurring GAA repeats in the first intron of the FXN gene, encoding for frataxin, a protein implicated in the biogenesis of iron-sulfur clusters. As the genetic defect interferes with FXN transcription, FRDA patients express a normal frataxin protein but at insufficient levels. Thus, current therapeutic strategies are mostly aimed to restore physiological FXN expression. We have previously described SINEUPs, natural and synthetic antisense long non-coding RNAs, which promote translation of partially overlapping mRNAs through the activity of an embedded SINEB2 domain. Here, by in vitro screening, we have identified a number of SINEUPs targeting human FXN mRNA and capable to up-regulate frataxin protein to physiological amounts acting at the post-transcriptional level. Furthermore, FXN-specific SINEUPs promote the recovery of disease-associated mitochondrial aconitase defects in FRDA-derived cells. In summary, we provide evidence that SINEUPs may be the first gene-specific therapeutic approach to activate FXN translation in FRDA and, more broadly, a novel scalable platform to develop new RNA-based therapies for haploinsufficient diseases.