Co-Exposure of Cardiomyocytes to IFN-γ and TNF-α Induces Mitochondrial Dysfunction and Nitro-Oxidative Stress...., 2021, Nunes et al

[Andy]

Full title: Co-Exposure of Cardiomyocytes to IFN-γ and TNF-α Induces Mitochondrial Dysfunction and Nitro-Oxidative Stress: Implications for the Pathogenesis of Chronic Chagas Disease Cardiomyopathy

Infection by the protozoan Trypanosoma cruzi causes Chagas disease cardiomyopathy (CCC) and can lead to arrhythmia, heart failure and death. Chagas disease affects 8 million people worldwide, and chronic production of the cytokines IFN-γ and TNF-α by T cells together with mitochondrial dysfunction are important players for the poor prognosis of the disease. Mitochondria occupy 40% of the cardiomyocytes volume and produce 95% of cellular ATP that sustain the life-long cycles of heart contraction. As IFN-γ and TNF-α have been described to affect mitochondrial function, we hypothesized that IFN-γ and TNF-α are involved in the myocardial mitochondrial dysfunction observed in CCC patients.

In this study, we quantified markers of mitochondrial dysfunction and nitro-oxidative stress in CCC heart tissue and in IFN-γ/TNF-α-stimulated AC-16 human cardiomyocytes. We found that CCC myocardium displayed increased levels of nitro-oxidative stress and reduced mitochondrial DNA as compared with myocardial tissue from patients with dilated cardiomyopathy (DCM). IFN-γ/TNF-α treatment of AC-16 cardiomyocytes induced increased nitro-oxidative stress and decreased the mitochondrial membrane potential (ΔΨm).

We found that the STAT1/NF-κB/NOS2 axis is involved in the IFN-γ/TNF-α-induced decrease of ΔΨm in AC-16 cardiomyocytes. Furthermore, treatment with mitochondria-sparing agonists of AMPK, NRF2 and SIRT1 rescues ΔΨm in IFN-γ/TNF-α-stimulated cells. Proteomic and gene expression analyses revealed that IFN-γ/TNF-α-treated cells corroborate mitochondrial dysfunction, transmembrane potential of mitochondria, altered fatty acid metabolism and cardiac necrosis/cell death. Functional assays conducted on Seahorse respirometer showed that cytokine-stimulated cells display decreased glycolytic and mitochondrial ATP production, dependency of fatty acid oxidation as well as increased proton leak and non-mitochondrial oxygen consumption. Together, our results suggest that IFN-γ and TNF-α cause direct damage to cardiomyocytes’ mitochondria by promoting oxidative and nitrosative stress and impairing energy production pathways.

We hypothesize that treatment with agonists of AMPK, NRF2 and SIRT1 might be an approach to ameliorate the progression of Chagas disease cardiomyopathy.

Open access, https://www.frontiersin.org/articles/10.3389/fimmu.2021.755862/full

 

[Hutan]

Functional assays conducted on Seahorse respirometer showed that cytokine-stimulated cells display decreased glycolytic and mitochondrial ATP production, dependency of fatty acid oxidation as well as increased proton leak and non-mitochondrial oxygen consumption.

Thanks for posting Andy. I thought this was interesting, the findings seem similar to what I remember researchers have reported about the mitochondria of people with ME/CFS. I also remember someone, I think Ron Davis, reporting that the epigenetic profile of people with ME/CFS looked like that of people with trypanosomiasis.

Although I think there have been some reports of cardiomyopathy in people with ME/CFS, I don't think it's a common or consistent finding.

(This is a fast and loose post, based on half-remembered facts. I hope others will add more substance.)

 

[Hutan]

To investigate the role of IFN-γ and TNF-α on AC-16 cardiomyocytes, we stimulated the cells with several concentrations of IFN-γ and TNF-α and we measured the mitochondrial ΔΨm in a high content screening platform. This was performed to stablish the concentrations of the cytokines for subsequent analyses. We observed that IFN-γ impaired the ΔΨm of AC-16 48h after stimulation and this impairment was enhanced when IFN-γ was combined with TNF-α; TNF-α alone failed to cause statistically significant reductions in ΔΨm

It is not clear to me exactly what they are saying about the timeline here, but it seems that stimulation of the cells with IFN-y reduced mitochondrial membrane potential. This would result in the mitochondria not being able to produce energy. Maybe this would fit with PEM?

 

[Hutan]

Another study, 2011
Effects of Trypanosoma cruzi infection on myocardial morphology, single cardiomyocyte contractile function and exercise tolerance in rats

Few studies have evaluated exercise performance and the factors affecting functional capacity and exercise tolerance in patients with Chagas’ disease. Moreover, it is not known whether T. cruziinfection can also lead to changes in exercise tolerance in experimental animal models. The reduction of exercise tolerance in individuals with Chagas’ disease is multifactorial and is involved with pathological changes in several organs and tissues, such as peripheral nervous system, skeletal and cardiac muscles (Meiler et al. 1987; Montes de Oca et al. 2004). Moreover, previous studies indicated that atrial and ventricular mechanical and electrical abnormalities may have an important role in exercise intolerance in Chagas’ disease (Gallo et al. 1975; Mady et al. 2000; Lima et al. 2010). However, several aspects of the cellular and molecular basis of these changes remain to be clarified.

They infected rats with Chagas, and later had them run to exhaustion. 48 hours after the exercise, they took muscle cells and investigated their ability to contract.

The linear regression analysis showed a moderate and significant correlation between the amplitude of cell shortening in basal and ISO-stimulated conditions and the workload of IG and CG animals in the exercise tolerance protocol

So, the amount of exercise that a rat was exposed to helped to predict the reduction in the later capacity of the cell to contract. The authors suggest other factors may also be involved, such as nerve damage.

Our results confirmed our hypothesis that T. cruzi infection is able to impair myocardium morphology and single cardiomyocyte contractile function and influence negatively the exercise tolerance in the murine model investigated.

I find this interesting, because there are times when I cannot get my muscles to have power. I notice this most when walking up steps, especially when carrying bags of groceries. Sometimes I can walk up the steps easily, but often there is an extremely noticeable lack of power. I'm sure that this is a real effect and not the impact of my imagination. Because of the variability, I don't think it's a lack of fitness.

In addition, the chronotropic incompetence caused by changes in the sympathetic and parasympathetic tonus induced by an immune-mediated process has been recognized as one of the mechanisms capable of interfering with the capacity of the heart to increase heart rate in response to different stimuli, including physical exercise

The presence of inflammatory infiltrate and mast cells 9 weeks after infection with T. cruzi favour this hypothesis because the continuous production of cytokines and oxidant components by these cells in a chronic inflammatory process may be conducive to vascular dysfunction. Indeed, mechanisms such as endothelial dysfunction, persistence of T. cruziantigens and release of nitric oxide associated with the chronic inflammatory process have been implicated in vascular dilatation and dysfunction of Chagas’ disease

That study talks about how increased physical fitness in healthy individuals has been found to be associated with increased sensitivity and density of calcium ion channels, and that problems with calcium channels have been linked to exertion intolerance.

There's even mention of issues with adrenergic receptors which have been hypothesised about in ME/CFS.

Data exist to support the role of the immune system in pathological remodelling of cardiomyocyte contractility (Sterin-Borda et al. 1999; Chakraborti et al.2000; Afanasyeva et al. 2004), including Chagas’ disease (Roman-Campos et al. 2009). It has been demonstrated that in humans and experimental animals with Chagas’ disease, anti-β-adrenoreceptor antibodies produced during infection by T. cruzi can inhibit the signalling pathway triggered by these receptors (Sterin-Borda et al. 1999; Chakraborti et al. 2000). Under normal conditions, β-adrenergic pathways lead to the phosphorylation and inhibition of PLB, which reduces its activity on SERCA-2 and improves inotropic, lusitropic and chronotropic activity of cardiomyocytes (Afanasyeva et al.2004). However, direct allosteric inhibition of β-adrenoreceptors by autoantibodies or desensitization mediated by upregulation of β-adrenergic receptor kinase may impair cardiomyocyte contractile function because this receptor is the main signalling pathway that regulates cellular mechanics through adjustments in Ca2+ kinetics. Furthermore, inhibition of β signalling reduces the phosphorylation and activation of RyR2 and Ca2+ entry into the cell via the L-type current mediated by the Ca2+-induced Ca2+-release mechanism (Afanasyeva et al. 2004).