A 2-day cardiopulmonary exercise test in chronic fatigue syndrome patients who were exposed to humidifier disinfectants, 2023, Leem et al

[Andy]

Abstract

Some survivors of humidifier disinfectants (HDs) complain of chronic, inexplicable fatigue, and post-exertional malaise (PEM). Two-day cardiopulmonary exercise tests (CPETs) performed 24 hours apart (2-day CPET protocol) are increasingly employed to evaluate PEM and related disabilities among individuals with chronic fatigue syndrome (CFS). The purpose of this study was to assess the reproducibility of CPET variables in individuals who had been exposed to HD and to show that 2-day CPET is an objective means of differentiating between fatigue conditions in people with CFS symptoms who have been exposed to HDs.

Twenty-nine HD survivors with CFS symptoms were enrolled in this study. To document and assess PEM in CFS, a 2-day CPET was conducted to measure baseline functional capacity (CPET1) and provoke PEM. Twenty-four hours later, a second CPET assessed changes in related variables, focusing on PEM effects on functional capacity. This CPET also measured changes in energy production and physiological function, objectively documenting PEM effects.

In the 2-day CPET, the peak oxygen consumption (VO2peak), VO2 at ventilatory threshold (VO2@VT), time to reach VO2peak, and time to reach VO2@VT were significantly decreased (p<0.001). The peak O2 pulse and O2 pulse at VT also decreased significantly (p<0.001). A 6-minute walk test revealed significantly decreased distance (p<0.01). This is the first study to conduct a 2-day consecutive CPET in previously exposed HD participants with CFS symptoms. Our results confirm previous work that demonstrated abnormal responses to PEM in CFS patients. Therefore, a 2-day CPET is an objective measure to differentiate fatigue conditions in people with CFS symptoms who have been exposed to HDs.

Open access, https://www.eaht.org/journal/view.php?doi=10.5620/eaht.2022033

 

[Peter T]

Interesting that this seems to involve a well documented group of ME/CFS cases not triggered by a viral infection.

Introduction

From 1994 to 2011, humidifier disinfectants (HDs), known to contain various harmful chemicals were used in Korea to prevent microbial growth in humidifier water tanks [1]. Approximately four million people have been exposed to HDs. Following an epidemic outbreak of interstitial lung disease characterized by spontaneous air leakage, rapid progression, and high mortality, HD inhalation was eventually identified as a major respiratory toxicant in 2011 [1,2]. Although fatal lung damage was initially reported, further investigations revealed that the damage was not limited to the lungs; systemic damage also occurred [3,4]. Among individuals with exposure to HDs, although a lung disease was not evident, some complained of chronic fatigue and post-exertional malaise (PEM) compared to healthy individuals. This condition presents a significant challenge for individuals to acquire and maintain employment, including normal activities of daily living.

… … …

Participants

Twenty-nine participants with a history of HD exposure and reported CFS symptoms were recruited from specialist clinics and support groups in South Korea. All participants were aged 18–65 years. CFS was diagnosed based on the Fukuda criteria [16]. For the 2-day CPET, participants whose cardiovascular status was determined to be “high-risk” were excluded, based on official guidelines for cardiovascular disease risk assessment [17]. Participants with comorbidities or orthopedic limitations that would affect their ability to complete a maximum treadmill test were excluded.

… … …

 

[Hutan]

The test-retest VO2peak and VO2@VT decrements in this study were considerably greater than the <7% variability, which has been reported consistently in healthy individuals [10,11]. Our data revealed a substantial decrease of 16.4% in the test-retest VO2@VT. This is consistent with the results of previous studies by VanNess et al. [6] (~26%), Keller et al. [9] (~16%), and Van Campen et al. [12,13] (~22%).

Oxidative stress and membrane-disrupting actions of polyhexamethylene guanidine phosphate (PHMG-p), which is one of the main toxic components in HDs, have been detected in smooth muscle cells, nerve tissues, and peripheral blood mononuclear cells [23–25]. Considering the spread of harmful chemicals of HDs from the lungs to the entire body, the toxic effects of PHMG-p are mainly attributable to mitochondrial dysfunction in various cell types [24,25]. Although the detailed mechanisms and etiology underlying CFS remain unclear, some evidence suggests that metabolic dysfunction caused by mitochondrial abnormalities could play a role [26–28]. Though we didn’t evaluate the mechanism of CFS in this study, mitochondrial dysfunction which was provoked by toxic materials in HDs could be a possible cause of CFS symptoms. Larger studies to evaluate the mechanism of CFS in HDs survivors are warranted.

We also observed a statistically significant test-retest decrease in peak O2 pulse of 4.9%, indicating a compromised oxygen delivery in CFS participants following PEM induction. O2 pulse, a surrogate measure for stroke volume and arteriovenous oxygen content difference, is an important index of cardiac function [30]. It is also a stable and reproducible measure over time in young athletes [31] and adult non-athletes [32]. Previous studies by Vermeulen et al. [8] and Keller et al. [9] found a significant decrease in maximal O2pulse and O2pulse at VT in patients with CFS. Additionally, they reported a lower arteriovenous oxygen content difference (determined non-invasively based on VO2 and cardiac output) and attributed these findings to lower muscular O2 extraction during exercise in CFS [33]. While it is unknown how alterations in oxygen delivery/utilization occur during a subsequent CPET in CFS patients, these results do suggest that the decrease in maximal O2pulse may partly explain the mitochondrial abnormalities suspected in CFS.

 

[Hutan]

About PHMG-p, one of the toxins in the humidifier disinfectants:
Polyhexamethylene guanidine phosphate-induced ROS-mediated DNA damage caused cell cycle arrest and apoptosis in lung epithelial cells

Polyhexamethylene guanidine phosphate (PHMG-p) is an active ingredient of humidifier disinfectants and causes severe lung injury resulting in pulmonary fibrosis. Current evidence indicates that pulmonary fibrosis is initiated as a result of epithelial damage, which can lead to an inflammatory response and fibrotic cell infiltration; however, the toxic mechanism of PHMG-p on the epithelium is still unknown. In this study, the toxic response of PHMG-p on human lung epithelial cells was evaluated, and its mechanisms associated with reactive oxygen species (ROS), DNA damage, and its relationship with p53 activation were investigated. The toxic responses of epithelial cells were assessed by flow cytometry analysis and western blot analysis. The results revealed that PHMG-p induced G1/S arrest and apoptosis in A549 cells. Interestingly, p53 was activated by PHMG-p treatment and p53 knockdown suppressed PHMG-p-induced apoptosis and cell cycle arrest. PHMG-p promoted ROS generation and consequently increased the expression of DNA damage markers such as ATM and H2AX phosphorylation. The antioxidant N-acetylcysteine reduced the expression of phosphorylated ATM and H2AX, and the ATM inhibitor, caffeine, inhibited p53 activation. Taken together, our results demonstrate that PHMG-p triggered G1/S arrest and apoptosis through the ROS/ATM/p53 pathway in lung epithelial cells.

 

[forestglip]

Although fatal lung damage was initially reported, further investigations revealed that the damage was not limited to the lungs; systemic damage also occurred [3,4]. Among individuals with exposure to HDs [humidifier disinfectants], although a lung disease was not evident, some complained of chronic fatigue and post-exertional malaise (PEM) compared to healthy individuals.

None of the sources about HDs in the intro where they discuss a potential link even mention CFS or PEM. (Edit: Seems to be based on a survey mentioned in reference 25.)

They didn’t recruit based on if the CFS symptoms came after HD exposure, as far as I can tell:

Twenty-nine participants with a history of HD exposure and reported CFS symptoms were recruited from specialist clinics and support groups in South Korea.

They make it clear they are testing in people who had CFS symptoms and also have been exposed to HDs, and don't say one preceded or caused the other:

Therefore, a 2-day CPET is an objective measure to differentiate fatigue conditions in people with CFS symptoms who have been exposed to HDs.

Edit: Though reference 25 says this:

According to a recent survey [9], the high prevalence of symptoms or chronic diseases, such as ophthalmologic diseases, nasal diseases, cardiovascular disease, chronic fatigue, attention-deficit/hyperactivity disorder (ADHD), and developmental disorders, may be related to HDs.

They're basing it on this survey:

Korean Society of Epidemiology Household survey for the victims due to humidifier disinfectants. 2020

But I can't find that online.

 

[Hutan]

They didn’t recruit based on if the CFS symptoms came after HD exposure, as far as I can tell:

Yes, good point. These researchers could have had an exclusion criteria for anyone who had CFS symptoms before humidifier disinfectant exposure, and perhaps they did, but they don't report it.

Even so, because the exposure to humidifier disinfectant probably occurred over a long time, if someone developed (ME)/CFS as a result of some other cause, they might still attribute it to humidifier disinfectant. That would be particularly likely if the onset did not clearly follow an infection, if HD illness had a higher profile than CFS, and if it looked as though people with HD illness might be receiving support of some sort. We've seen something like that with Long Covid. Long Covid is much better known and more accepted. And so people who have developed ME/CFS since 2020 are likely to self-identify as having Long Covid.

The authors appear to be careful throughout their paper to not say that their participants have CFS caused by exposure to HD, so perhaps they too had some concerns about this issue.

 

[Hutan]

That said, I do find the p53 activation reported to happen after exposure to PHMG-p (as reported in my post upthread) interesting. I don't know why the researchers in that study chose to investigate p53.

p53 and the associated TP53 have been mentioned a number of times in ME/CFS literature, although I'm not sure if it is consistently higher levels, or consistently more activated. Googling, I find this:

Although p53 keeps [cancer] cells from taking over, too much of the protein might cause trouble. In addition to stalling or killing cultured cells, the protein can send them into a zombielike state known as senescence, in which they permanently stop dividing but don't die.

Also this;

Dial 9-1-1 for p53: Mechanisms of p53 Activation by Cellular Stress

The tumor suppressor protein, p53, is part of the cell's emergency team that is called upon following cellular insult. How do cells sense DNA damage and other cellular stresses and what signal transduction pathways are used to alert p53? How is the resulting nuclear accumulation of p53 accomplished and what determines the outcome of p53 induction? Many posttranslational modifications of p53, such as phosphorylation, dephosphorylation, acetylation and ribosylation, have been shown to occur following cellular stress. Some of these modifications may activate the p53 protein, interfere with MDM2 binding and/or dictate cellular localization of p53. This review will focus on recent findings about how the p53 response may be activated following cellular stress.

Taken together, regulation of p53 transcription and translation may contribute to p53 accumulation following certain types of stresses. Moreover, the suppressive role of p53 on its own transcription and translation sets up an interesting negative feedback loop where accumulation of p53 following cellular stress would lead to the shutdown of both its own transcription and translation (Figure 6). This would ensure that the p53 response is turned off shortly after the damage responsible for triggering the response has been repaired.

Following cellular stresses that induce the activation of JNK, the JNK-mediated ubiquitylation and degradation of p53 are abolished [140]. Activated JNK actually phosphorylates p53 leading to the attenuation of the interaction between p53 and MDM2. Thus, kinases upstream of JNK may be critical regulators of p53 stability by controlling both JNK- and MDM2-mediated ubiquitylation of p53

What is different about the regulation of p53 in epithelial cells compared to fibroblasts [262–264]? How important are the inhibitory effects of p53 function by environmental pollutants such as arsenic [265] and cadmium [266] for human health?

More than 15,000 papers featuring p53 have been published since its discovery in 1979 [267–269]. About 10 papers are currently published daily. With this productivity in both basic and clinical research, there are good prospects that our further understanding of the regulation and function of p53 soon will lead to fruitful new efforts in both the prevention and treatment of cancer.

It's really complicated and still incompletely understood. Many things cause p53 to accumulate and be active, lots of cell stressors including viral infections, nitric oxide and hypoxia.

Perhaps just something to keep an eye out for.

 

[SNT Gatchaman]

Also the WASF3 study and findings came about due to investigation of a patient with a germline TP53 mutation causing Li-Fraumeni syndrome. Although WASF3 protein over-expression was thought to be unrelated.

Some other recent p53 papers on the to-read list —

p53 enables phospholipid headgroup scavenging (2024)
Jossie Yashinskie; Xianbing Zhu; Grace McGregor; Katrina Paras; Benjamin Jackson; Abigail Xie; Richard Koche; Christian Metallo; Lydia Finley

Changes in cell state are often accompanied by altered metabolic demands, and homeostasis depends on cells adapting to their changing needs. One major cell state change is senescence, which is associated with dramatic changes in cell metabolism, including increases in lipid metabolism, but how cells accommodate such alterations is poorly understood.

Here, we show that the transcription factor p53 enables recycling of the lipid headgroups required to meet the increased demand for membrane phospholipids during senescence. p53 activation increases supply of phosphoethanolamine (PEtn), an intermediate in the Kennedy pathway for de novo synthesis of phosphatidylethanolamine (PE), by transactivating genes involved in autophagy and lysosomal catabolism that enable membrane turnover.

Disruption of PEtn conversion to PE is well-tolerated in the absence of p53 but results in dramatic organelle remodeling and perturbs growth and gene expression following p53 activation. Consistently, CRISPR-Cas9-based genetic screens reveal that p53-activated cells preferentially depend on genes involved in lipid metabolism.

Together, these results reveal lipid headgroup recycling to be a homeostatic function of p53 that confers a cell-state specific metabolic vulnerability.


Link | PDF (Preprint: BioRxiv) [Open Access]


p53: A tale of complexity and context (2024)
Moshe Oren; Carol Prives

The story of p53 is illuminating. Despite widespread attention, the tumor-suppressive functions of wild-type p53 or the oncogenic activities of its cancer-associated mutants are still not fully understood, and our discoveries have not yet led to major therapeutic breakthroughs. There is still much to learn about this fascinating protein.


Link | PDF (Cell)