Altered mitochondrial respiration in peripheral blood mononuclear cells of post-acute sequelae of SARS-CoV-2 infection, 2024, Dirajlal-Fargo et al.

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Altered mitochondrial respiration in peripheral blood mononuclear cells of post-acute sequelae of SARS-CoV-2 infection
Dirajlal-Fargo; Maison; Durieux; Andrukhiv; Funderburg; Ailstock; Gerschenson; Mccomsey

Peripheral blood mononuclear cells (PBMC) mitochondrial respiration was measured ex vivo from participants without a history of COVID (n=19), with a history of COVID and full recovery (n= 20), and with PASC (n=20). Mean mitochondrial basal respiration, ATP-linked respiration, maximal respiration, spare respiration capacity, ATP-linked respiration, and non-mitochondrial respiration were highest in COVID+ PASC+ (p≤0.04).

Every unit increase in non-mitochondrial respiration, ATP-linked respiration, basal respiration, spare respiration capacity, and maximal respiration increased the predicted odds of PASC between 1% and 6%.

Mitochondrial dysfunction in PBMCs may be contributing to the etiology of PASC.

Link | PDF (Mitochondrion)

 

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Figure 4: Comparison of Mitochondrial Respiration between COVID-, COVID+ No PASC, and COVID+ PASC+.

This figure represents the results of the MitoStress experiment. A) A representative trace of mitochondrial respiration and the differences between COVID+PASC+ (pink), COVID+ No PASC (blue), and COVID- (black). The traces are obtained using an XFe96 analyzer and Mito Stress Test Kit that utilizes oligomycin (orange), FCCP (green), rotenone, and antimycin A (yellow) sequentially to calculate basal respiration, ATP-linked respiration, proton leak, maximal respiration, spare capacity, and non-mitochondrial oxygen consumption. A generalized linear model was used to compare the groups, and the results are shown for B) basal respiration, C) maximal respiration, D) ATP-linked respiration, E) spare respiratory capacity, and F) non-mitochondrial respiration.

 

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Selected, abridged quotes from discussion —

To our knowledge, this study is the first ex vivo study to evaluate the effects of mitochondrial function and demonstrate altered function in PBMCs among PASC.

Compared to COVID+ no PASC, the proportion of respiration linked to ATP-linked respiration was significantly higher among PASC. Increases in basal respiration, ATP-linked respiration, maximal respiration, spare respiratory capacity, and non-mitochondrial respiration were associated with increases in the likelihood of PASC. Glycolysis, as measured by ECAR, was not different among the participants. These findings suggest that the energetic needs of PASC PBMC are greater than COVID+ no PASC and COVID- PBMC.

our findings that mitochondria in PASC PBMC exhibit increased oxygen consumption could explain the discoveries of lactic acidosis and impaired fatty acid oxidation in PASC persons during physical activity. As the elevated oxygen consumption in the blood would reduce the amount of oxygen available for muscles. This anaerobic environment would increase muscular glycolysis, produce more lactic acid, and impair mitochondrial dependent lipid catabolism.

circulating antigens could stimulate monocytes to produce an omnipresent state of inflammation, requiring increased ATP-linked respiration and leading to the symptoms of PASC. Yet, we did not observe increased inflammation, gut permeability, or monocyte activation markers in PASC systemically in the plasma or serum.

hematopoietic stem/progenitor cells (HSC) highly express ACE2 and TMPRSS2, making them susceptible to SARS-CoV-2 during the initial infection. [...] Additionally, SARS-CoV-2 RNA has been detected in the bone marrow of post-mortem samples. PBMC lack ACE2 receptor expression and do not support productive SARSCoV-2 infection but generate a monocyte-accentuated immune response upon stimulation with SARSCoV-2 [...] findings of altered mitochondrial function in PBMC support the residual reservoir and immune dysregulation theories of PASC pathogenesis

In combination, these understandings lead to a probable second hypothesis from this work: that reservoirs of viral RNA and proteins in HSC, upon HSC differentiation, remain in PBMC and lead to altered PBMC mitochondrial function through immune activation, sustained inflammation, and the symptoms seen in PASC. Thus, the longevity of PASC would be relative to the extent of HSC viral infiltration

 

[SNT Gatchaman]

cf An Isolated Complex V Inefficiency and Dysregulated Mitochondrial Function in Immortalized Lymphocytes from ME/CFS Patients (2020, International Journal of Molecular Sciences). That paper used EBV-immortalised lymphoblastoid cells and went in-depth into the components of the ETC, suggesting wide-scale compensations for impaired ATP production by complex V. This paper looks to be smaller in scale and doesn't focus on the components of the ETC, but does look to me to have some similar findings.

the proportion of respiration linked to ATP-linked respiration was significantly higher among PASC.

mitochondrial respiratory capacity in ME/CFS lymphoblasts is upregulated, perhaps in response to inefficient ATP synthesis by Complex V.

We conclude that mean basal respiration, ATP-linked respiration, maximal respiration, spare respiratory capacity, proton leak, non-mitochondrial respiration are highest in PASC PBMC.

The inefficiency of ATP synthesis by Complex V means that basal respiration rates by ME/CFS lymphoblast mitochondria would also be reduced, were it not for the compensatory upregulation of their respiratory complex levels. This allows them to maintain normal ATP synthesis rates and, as observed, is accompanied by increased respiratory capacity of the electron transport chain (mostly Complex I activity), supported by an increased use of the proton gradient to drive mitochondrial protein import and other mitochondrial membrane transport processes (the “proton leak”).

Glycolysis, as measured by ECAR, was not different among the participants.

To investigate glycolysis in intact ME/CFS lymphoblasts, we modified and implemented an optimized Seahorse assay to assess real-time glycolytic production of lactate in live cells by measuring the extracellular acidification rate (ECAR) of the medium. We found no difference between ME/CFS and control cells in glycolytic rate, reserve or capacity

I didn't see any ME/CFS literature referenced and I don't think it was even mentioned, though they report that 75% of the patients had fatigue, 55% PEM, 65% orthostatic intolerance.

@DMissa previously you have commented on the importance of cell type, handling, timing of evaluation etc, so I don't know how this study should be viewed in comparison. These were "generic" PBMCs, frozen and shipped from Ohio to Hawaii.

Blood was obtained from each subject in a fasting state defined as nothing by mouth except water for ≥12 h prior to the blood draw and was collected in EDTA vacutainer tubes. PBMCs were isolated over a Ficoll-Paque and washed three times with phosphate-buffered saline (PBS). [...] Cells were then viably cryopreserved [...]. Cells were shipped from University Hospitals Cleveland Medical Center to the University of Hawaii on dry ice and kept in a liquid nitrogen dewar until assayed. Cell count and viability were determined [...]. Complete blood count (CBC) and differential were obtained in real-time at the local CLIA-certified laboratory at University Hospitals Cleveland Medical Center, Cleveland, Ohio for measurement of total lymphocyte and monocyte count.