Dolphin
Senior Member (Voting Rights)
Via Dr. Marc-Alexander Fluks
Source: University of Stavanger
Date: September 2, 2020
URL: https://uis.brage.unit.no/uis-xmlui/handle/11250/2675917
https://uis.brage.unit.no/uis-xmlui/bitstream/handle/11250/2675917/Kjetil_Baardsen_PhD.pdf
Interleukin-1beta, heat shock protein 90alpha, and hypocretin-1 in
chronic fatigue
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Kjetil Bardsen
- Department of Chemistry, Bioscience and Environmental Engineering,
Faculty of Science and Technology, University of Stavanger,
NO-4036 Stavanger, Norway
Abstract
Background
Fatigue, defined as an overwhelming sense of tiredness, lack of energy,
and feeling of exhaustion, is a phenomenon many people have experienced
in connection with infections such as influenza, Epstein-Barr virus,
etc. Fatigue is also common in cancer, neurological conditions like
multiple sclerosis, Parkinson's disease, and in chronic inflammatory and
autoimmune diseases such as rheumatoid arthritis, psoriasis, and others.
'Sickness behavior' observed in animals is a conceptual model for
understanding fatigue. In this model, infection or tissue damage is
followed by behavioral changes like social withdrawal, inactivity,
sleepiness, fatigue, and reduced food and water intake. The
proinflammatory cytokine interleukin (IL)-1beta produced during
activation of innate immune cells has a prominent role in mediating this
behavior. IL-1beta crosses the blood-brain barrier and in the brain
IL-1beta amplifies its own signaling by inducing microglia to produce
IL-1beta. In cerebral neurons IL-1beta signals through a receptor
complex including interleukin-1 receptor I (IL-1RI) and an alternative
IL-1 receptor accessory protein that does not mediate inflammation but
induce neuronal activation and sickness behavior.
The inflammatory response needs to be controlled and is therefore
downregulated in a timely manner not to run rampant. In addition,
cellular protection mechanisms are activated during inflammation and
tissue damage to preserve cellular life from reactive molecules that
kill pathogens. Some variants of heat shock proteins (HSPs) released
into the extracellular space could represent a defense mechanism of
cellular life that also influence fatigue mechanisms.
In addition, sleepiness and weariness are closely related to fatigue and
part of the sickness behavior response. Inflammation can alter sleep
patterns. The master regulator of sleep- and wakefulness, neuropeptide
hypocretin-1 (Hcrt1), could therefore have a role in fatigue generation.
Objectives
I) Investigate if mechanisms that protect cellular life and homeostasis
are involved in the generation of fatigue.
II) Develop a non-radioactive, sensitive and selective method for
measurement of Hcrt1 in cerebrospinal fluid (CSF).
III) Explore how IL-1beta and other selected molecules interact in
generation of fatigue, and to investigate a possible link between the
neuropeptide Hcrt1 and fatigue.
Methods
To explore mechanism of fatigue, a cohort of 71 patients with primary
Sjogren's syndrome were investigated. CSF samples where available from
49 patients. A method based on liquid chromatography coupled with tandem
mass spectrometry (LC-MS/MS) was developed for measurements of Hcrt1.
Hcrt1 was measured in CSF samples from 22 healthy subjects and 9
patients with narcolepsy type 1.
The clinical variables fatigue, depression and pain were scored using
the fatigue Visual Analogue Scale (fVAS), Beck Depression Inventory, and
the pain item of the Medical Outcome Survey short form 36, respectively.
ELISAs were used to measure HSP32, -60, -72, and -90alpha in plasma, and
in CSF to measure concentrations of IL-1Ra, IL-1RII, IL-6, and the
calcium binding protein S100B. Hcrt1 in CSF was measured using a
radioimmunoassay (RIA) method, in addition to a non-radioactive method
based on liquid chromatography coupled with tandem mass spectrometry.
Results were analyzed by non-parametric group comparisons, logistic
regression, univariate- and multiple regression, and principal component
analysis (PCA).
Results
Measures of HSP32, -60, -72, and -90alpha in plasma revealed that the
concentrations of HSP90alpha were significantly higher in pSS patients
with high fatigue versus low fatigue. A tendency toward higher
concentrations of HSP72 was observed in patients with high fatigue
compared to patients with low fatigue.
The LC-MS/MS method for Hcrt1 in CSF revealed much lower
concentrations in healthy subjects than what has previously been
published. Patients with narcolepsy type 1, a sleep disorder
characterized by low levels of Hcrt1 in CSF, also had lower levels of
Hcrt1 in CSF compared to previous published studies. The LC-MS/MS method
was compared to the commonly used RIA method. A Bland-Altman plot showed
agreement between the two methods.
Analysis of IL-1beta related proteins (IL-1Ra, IL-1RII, and S100B),
IL-6, and Hcrt1 in CSF demonstrated that IL-1Ra showed significant
association with fVAS scores together with the clinical variables BDI
scores and pain scores. The relationship of the biochemical variables
was explored in PCA, and two significant components appeared: Variables
related to IL-1beta activity dominated the first component while in the
second component there was a negative association between IL-6 and
Hcrt1. Fatigue was introduced as an additional variable in a second
model. In this PCA, fVAS scores were associated with the first component
as was the IL-1beta related variables. In addition, the second PCA model
revealed a third component that showed a negative relationship between
Hcrt1 and fatigue.
Conclusions:
I) HSP90alpha and to a lesser degree HSP72 in blood may possibly be
parts of a fatigue inducing mechanism.
II) The LC-MS/MS method with high selectivity and accuracy revealed
considerably lower levels of Hcrt1 in CSF than previously reported.
III) IL-1beta signaling is a primary driver in fatigue. Several other
proteins and molecules interact with IL-1beta in a complex network, in
which several cell types (neurons, microglia, and astrocytes) probably
participate.
IV) Hcrt1 also influences fatigue, but probably through another pathway
than the IL-1 route.
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