ANALYSIS OF MITOCHONDRIAL DNA CYTOCHROME-B (CYB) and ATPase-6 GENE MUTATIONS IN COVID-19 PATIENTS

Whole mitogenome sequencing uncovers a relation between mitochondrial heteroplasmy and leprosy severity

BACKGROUND

In recent years, the mitochondria/immune system interaction has been proposed, so that variants of mitochondrial genome and levels of heteroplasmy might deregulate important metabolic processes in fighting infections, such as leprosy.

METHODS

We sequenced the whole mitochondrial genome to investigate variants and heteroplasmy levels, considering patients with different clinical forms of leprosy and household contacts. After sequencing, a specific pipeline was used for preparation and bioinformatics analysis to select heteroplasmic variants.

RESULTS

We found 116 variants in at least two of the subtypes of the case group (Borderline Tuberculoid, Borderline Lepromatous, Lepromatous), suggesting a possible clinical significance to these variants. Notably, 15 variants were exclusively found in these three clinical forms, of which five variants stand out for being missense (m.3791T > C in MT-ND1, m.5317C > A in MT-ND2, m.8545G > A in MT-ATP8, m.9044T > C in MT-ATP6 and m.15837T > C in MT-CYB). In addition, we found 26 variants shared only by leprosy poles, of which two are characterized as missense (m.4248T > C in MT-ND1 and m.8027G > A in MT-CO2).

CONCLUSION

We found a significant number of variants and heteroplasmy levels in the leprosy patients from our cohort, as well as six genes that may influence leprosy susceptibility, suggesting for the first time that the mitogenome might be involved with the leprosy process, distinction of clinical forms and severity. Thus, future studies are needed to help understand the genetic consequences of these variants.

Possible Pathogenesis and Prevention of Long COVID: SARS-CoV-2-Induced Mitochondrial Disorder

Patients who have recovered from coronavirus disease 2019 (COVID-19) infection may experience chronic fatigue when exercising, despite no obvious heart or lung abnormalities. The present lack of effective treatments makes managing long COVID a major challenge. One of the underlying mechanisms of long COVID may be mitochondrial dysfunction. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections can alter the mitochondria responsible for energy production in cells. This alteration leads to mitochondrial dysfunction which, in turn, increases oxidative stress. Ultimately, this results in a loss of mitochondrial integrity and cell death. Moreover, viral proteins can bind to mitochondrial complexes, disrupting mitochondrial function and causing the immune cells to over-react. This over-reaction leads to inflammation and potentially long COVID symptoms. It is important to note that the roles of mitochondrial damage and inflammatory responses caused by SARS-CoV-2 in the development of long COVID are still being elucidated. Targeting mitochondrial function may provide promising new clinical approaches for long-COVID patients; however, further studies are needed to evaluate the safety and efficacy of such approaches.

"Mitochondrial pathogenic mutations and metabolic alterations associated with COVID-19 disease severity"

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) caused global pandemic and drastically affected the humankind. Mitochondrial mutations have been found to be associated with several respiratory diseases. Missense mutation and pathogenic mitochondrial variants might unveil the potential involvement of the mitochondrial genome in coronavirus disease 2019 (COVID-19) pathogenesis. The present study aims to elucidate the role of mitochondrial DNA (mtDNA) mutations, mitochondrial haplogroup, and energy metabolism in disease severity. The study was performed on 58 subjects comprising COVID-19-positive (n = 42) and negative (n = 16) individuals. COVID-19-positive subjects were further categorized into severe deceased (SD), severe recovered (SR), moderate (Mo), and mild (Mi) patients, while COVID-19-negative subjects were healthy control (HC) for the study. High throughput next-generation sequencing was done to investigate mtDNA mutations and haplogroups. The computational approach was applied to study the effect of mtDNA mutations on protein secondary structure. Real time polymerase chain reaction was used for mtDNA copy number determination and mitochondrial function parameters were also analyzed. We found 15 mtDNA mutations in MT-ND5, MT-ND4, MT-ND2, and MT-COI genes uniquely associated with COVID-19 severity affecting the secondary structure of proteins in COVID-19-positive subjects. Haplogroup analysis suggests that mtDNA haplogroups M3d1a and W3a1b might be potentially associated with COVID-19 pathophysiology. The mitochondrial function parameters were significantly altered in severe patients (SD and SR; p < 0.05). No significant relationship was found between mtDNA mutations and oxidative stress markers (p > 0.05). The study highlights the importance of mitochondrial reprogramming in COVID-19 patients and may provide a feasible approach toward finding a path for therapeutic interventions to COVID-19 disease.

Şizofreni hastalarında CYB mtDNA mutasyonları ve PI3K/AKT/mTOR sinyal yolağındaki genlerin ekspresyon durumu

Amaç: Bu çalışma, şizofreni hastalarında sitokrom b (CYB) mitokondriyal DNA (mtDNA) mutasyonlarını taramayı ve PI3K/AKT/mTOR sinyal yolağındaki genlerin mRNA ifadelerini analiz etmeyi amaçlamıştır. Gereç ve Yöntem: Bu çalışmada 44 şizofreni hastasından ve 41 sağlıklı bireyden DNA (hasta) ve RNA (hasta ve kontrol) izolasyonu için tam kan alındı. CYB mtDNA mutasyonları için örnekler PCR ile amplifiye edildi ve Sanger DNA dizi analiziyle tanımlandı. PIK3CA, AKT1 ve mTOR genlerinin mRNA ekspresyonu için RT-PCR ve 2-∆∆Ct metodu kullanıldı. Bulgular: Şizofreni hastalarında m.15326 A>G (43/44), m.15452 C>A (5/44), m.15078 A>G (3/44), m.14872 C>T (3/44) ve m.14798 T>C (3/44) en sık rastalanan CYB mtDNA mutasyonlarıydı. İn silico analizler, mutasyonların bir kısmının zararlı, hastalık yapıcı veya benign karakterle ilişkili olduğunu gösterdi. Şizofreni hastalarında PIK3CA, AKT1 ve mTOR genlerinin mRNA ekspresyonu sağlıklı bireylere göre anlamlı derecede yüksekti. PIK3CA ve AKT1 genleri arasında anlamlı orta şiddette pozitif bir korelasyon tespit edildi. Ayrıca ROC analizi ile PIK3CA, AKT1 ve mTOR genlerinin hasta grubunda iyi tanısal güce sahip olduğu belirlendi. ROC analizleri, özellikle PIK3CA'nın şizofreni hastaları için % 80 duyarlılık ve % 63,4 seçicilik ile önemli bir tanı değerine sahip olduğunu gösterdi. Sonuç: Şizofreni hastalarında hem CYB mtDNA mutasyon sıklığı hem de PIK3CA, AKT1 ve mTOR mRNA ekspresyon düzeyi sağlıklı bireylere göre daha yüksekti. Bu mekanizmaları daha geniş şizofreni popülasyonunda çalışmanın hastalığın tanı, tedavi veya prognozunda değerli olabileceğine inanıyoruz.

NSP4 and ORF9b of SARS-CoV-2 Induce Pro-Inflammatory Mitochondrial DNA Release in Inner Membrane-Derived Vesicles

Circulating cell-free mitochondrial DNA (cf-mtDNA) has been found in the plasma of severely ill COVID-19 patients and is now known as a strong predictor of mortality. However, the underlying mechanism of mtDNA release is unexplored. Here, we show a novel mechanism of SARS-CoV-2-mediated pro-inflammatory/pro-apoptotic mtDNA release and a rational therapeutic stem cell-based approach to mitigate these effects. We systematically screened the effects of 29 SARS-CoV-2 proteins on mitochondrial damage and cell death and found that NSP4 and ORF9b caused extensive mitochondrial structural changes, outer membrane macropore formation, and the release of inner membrane vesicles loaded with mtDNA. The macropore-forming ability of NSP4 was mediated through its interaction with BCL2 antagonist/killer (BAK), whereas ORF9b was found to inhibit the anti-apoptotic member of the BCL2 family protein myeloid cell leukemia-1 (MCL1) and induce inner membrane vesicle formation containing mtDNA. Knockdown of BAK and/or overexpression of MCL1 significantly reversed SARS-CoV-2-mediated mitochondrial damage. Therapeutically, we engineered human mesenchymal stem cells (MSCs) with a simultaneous knockdown of BAK and overexpression of MCL1 (MSCshBAK+MCL1) and named these cells IMAT-MSCs (intercellular mitochondrial transfer-assisted therapeutic MSCs). Upon co-culture with SARS-CoV-2-infected or NSP4/ORF9b-transduced airway epithelial cells, IMAT-MSCs displayed functional intercellular mitochondrial transfer (IMT) via tunneling nanotubes (TNTs). The mitochondrial donation by IMAT-MSCs attenuated the pro-inflammatory and pro-apoptotic mtDNA release from co-cultured epithelial cells. Our findings thus provide a new mechanistic basis for SARS-CoV-2-induced cell death and a novel therapeutic approach to engineering MSCs for the treatment of COVID-19.