Plasma neuropeptide Y: a biomarker for symptom severity in chronic fatigue syndrome

BACKGROUND

Chronic fatigue syndrome (CFS) is a complex, multi-symptom illness with a multisystem pathogenesis involving alterations in the nervous, endocrine and immune systems.Abnormalities in stress responses have been identified as potential triggers or mediators of CFS symptoms. This study focused on the stress mediator neuropeptide Y (NPY). We hypothesized that NPY would be a useful biomarker for CFS.

METHODS

The CFS patients (n = 93) were from the Chronic Fatigue and Related Disorders Clinic at the University of Miami and met the 1994 case definition of Fukuda and colleagues. Healthy sedentary controls (n = 100)) were from NIH or VA funded studies. Another fatiguing, multi-symptom illness, Gulf War Illness (GWI), was also compared to CFS. We measured NPY in plasma using a radioimmunoassay (RIA). Psychometric measures, available for a subset of CFS patients included: Perceived Stress Scale, Profile of Mood States, ATQ Positive & Negative Self-Talk Scores, the COPE, the Beck Depression Inventory, Fatigue Symptom Inventory, Cognitive Capacity Screening Examination, Medical Outcomes Survey Short Form-36, and the Quality of Life Scale.

RESULTS

Plasma NPY was elevated in CFS subjects, compared to controls (p = .000) and to GWI cases (p = .000). Receiver operating characteristics (ROC) curve analyses indicated that the predictive ability of plasma NPY to distinguish CFS patients from healthy controls and from GWI was significantly better than chance alone. In 42 patients with CFS, plasma NPY had significant correlations (<0.05) with perceived stress, depression, anger/hostility, confusion, negative thoughts, positive thoughts, general health, and cognitive status. In each case the correlation (+ or -) was in the anticipated direction.

CONCLUSIONS

This study is the first in the CFS literature to report that plasma NPY is elevated compared to healthy controls and to a fatigued comparison group, GWI patients. The significant correlations of NPY with stress, negative mood, general health, depression and cognitive function strongly suggest that this peptide be considered as a biomarker to distinguish subsets of CFS.

Biomarkers in chronic fatigue syndrome: evaluation of natural killer cell function and dipeptidyl peptidase IV/CD26

BACKGROUND

Chronic Fatigue Syndrome (CFS) studies from our laboratory and others described decreased natural killer cell cytotoxicity (NKCC) and elevated proportion of lymphocytes expressing the activation marker, dipeptidyl peptidase IV (DPPIV) also known as CD26. However, neither these assays nor other laboratory tests are widely accepted for the diagnosis or prognosis of CFS. This study sought to determine if NKCC or DPPIV/CD26 have diagnostic accuracy for CFS.

METHODS/RESULTS

Subjects included female and male CFS cases and healthy controls. NK cell function was measured with a bioassay, using K562 cells and (51)Cr release. Lymphocyte associated DPPIV/CD26 was assayed by qualitative and quantitative flow cytometry. Serum DPPIV/CD26 was measured by ELISA. Analysis by receiver operating characteristic (ROC) curve assessed biomarker potential. Cytotoxic function of NK cells for 176 CFS subjects was significantly lower than in the 230 controls. According to ROC analysis, NKCC was a good predictor of CFS status. There was no significant difference in NK cell counts between cases and controls. Percent CD2+ lymphocytes (T cells and NK cells) positive for DPPIV/C26 was elevated in CFS cases, but there was a decrease in the number of molecules (rMol) of DPPIV/C26 expressed on T cells and NK cells and a decrease in the soluble form of the enzyme in serum. Analyses by ROC curves indicated that all three measurements of DPPIV/CD26 demonstrated potential as biomarkers for CFS. None of the DPPIV/C26 assays were significantly correlated with NKCC.

CONCLUSIONS

By ROC analysis, NKCC and three methods of measuring DPPIV/C26 examined in this study had potential as biomarkers for CFS. Of these, NKCC, %CD2+CD26+ lymphocytes and rMol CD26/CD2+ lymphocyte, required flow cytometry, fresh blood and access to a high complexity laboratory. Soluble DPPIV/C26 in serum is done with a standard ELISA assay, or with other soluble factors in a multiplex type of ELISA. Dipeptidyl peptidase IV on lymphocytes or in serum was not predictive of NKCC suggesting that these should be considered as non-redundant biomarkers. Abnormalities in DPPIV/CD26 and in NK cell function have particular relevance to the possible role of infection in the initiation and/or the persistence of CFS.

Basic calcium phosphate crystal-induced Egr-1 expression stimulates mitogenesis in human fibroblasts

Previously, we have reported that basic calcium phosphate (BCP) crystals stimulate mitogenesis and synthesis of matrix metalloproteinases in cultured human foreskin and synovial fibroblasts. However, the detailed mechanisms involved are still unclear. In the present study, using RT-PCR and Egr-1 promoter analysis we showed that BCP crystals could stimulate early growth response gene Egr-1 transcription through a PKCalpha-dependent p44/p42 MAPK pathway. Using a retrovirus gene expression system (Clontech) to overexpress Egr-1 in human fibroblast BJ-1 cells resulted in promotion of mitogenesis measured either by MTT cell proliferation analysis or by direct cell counting. The results demonstrate that Egr-1 may play a key role in mediating BCP crystal-induced synovial fibroblast mitogenesis.

Induction of early growth response gene Egr2 by basic calcium phosphate crystals through a calcium-dependent protein kinase C-independent p44/42 mitogen-activated protein kinase pathway

Using the reverse transcriptase-polymerase chain reaction we examined the effect of basic calcium phosphate (BCP) crystals on the induction of the early growth response gene Egr2 transcription and the signal transduction pathway involved. The results showed that BCP crystals induced Egr2 transcription up to 8-fold, peaking at 24 h after treatment. The induction of Egr2 was confirmed by transient transfection assays using an Egr2 promoter/luciferase reporter construct and could be inhibited by the p44/42 mitogen-activated protein kinase (MAPK)-specific inhibitor U0126, or by calcium chelator TMB-8, but not by the SAPK2/p38 MAPK inhibitor SB202190 or by the protein kinase C inhibitor bisindolylmaleimide I (Bis-I). Using the Mercury Pathway Profiling System (Clontech, Palo Alto, Calif., USA) we further showed that induced Egr2 could stimulate the activities of several transcription factors that are associated with cell proliferation, such as c-fos, SRF and c-myc.

Regulation of Bcl-xL: a little bit of this and a little bit of STAT

The Bcl-2 family of proteins are key regulators of apoptosis. Bcl-xL, is an anti-apoptotic protein with a high degree of homology to Bcl-2; however, the signals that regulate Bcl-xL and Bcl-2 appear to be different. Levels of Bcl-xL, but not Bcl-2, are increased in response to various survival signals. Furthermore, an inverse correlation between the levels of Bcl-2 and Bcl-xL has been reported for a number of cancers. Although the precise molecules that control Bcl-xL activity are unclear, the STAT, Rel/NF-kappaB, and Ets transcription factor families have recently been reported to directly regulate the bcl-x gene. Activated Ras, integrin, vitronectin, and hepatocyte growth factor signaling cascades have also been linked to changes in Bcl-xL expression. Bcl-xL can also be affected by post-translational mechanisms. Here we review recent advances in identifying the signaling pathways and factors involved in regulation of the bcl-x gene.

Tetraaquabis[2-(4-pyridyl)ethanesulfonato-N]zinc(II)

The title compound, [Zn(C(7)H(8)NO(3)S)(2)(H(2)O)(4)], has an octahedral coordination around the central Zn atom composed of two axial N atoms from the pyridine ligands and four equatorial O atoms of water molecules, forming a monomeric centrosymmetric complex. The two Zn-N bond distances are 2.102 (3) A, while the four Zn-O bond distances range from 2.114 (2) to 2.167 (2) A. Packing is determined by hydrogen bonds formed by the water molecules. The sulfonate group does not take part in coordination to the Zn atom.

Characterization of the p125 subunit of human DNA polymerase delta and its deletion mutants. Interaction with cyclin-dependent kinase-cyclins

The catalytic subunit of human DNA polymerase (pol) delta was overexpressed in an active, soluble form by the use of a baculovirus system in insect cells. The recombinant enzyme was separated from endogenous DNA polymerases by phosphocellulose, Mono Q-Sepharose, and single-stranded DNA-cellulose chromatography. Recombinant DNA pol delta was also purified by immunoaffinity chromatography. The enzymatic properties of the purified catalytic subunit were characterized. The enzyme was active and possessed both DNA polymerase and associated 3' to 5' exonuclease activities. NH2-terminal deletion mutants retained polymerase activity, whereas the core and COOH-terminal deletion mutants were devoid of any measurable activities. Coinfection of Sf9 cells with recombinant baculovirus vectors for pol delta and cyclin-dependent kinase (cdk)-cyclins followed by metabolic labeling with 32Pi showed that the recombinant catalytic subunit of pol delta could be hyperphosphorylated by G1 phase-specific cdk-cyclins. When cdk2 was coexpressed with pol delta in Sf9 cells, pol delta was found to coimmunoprecipitate with antibodies against cdk2. Experiments with deletion mutants of pol delta showed that the NH2-terminal region was essential for this interaction. Coimmunoprecipitation and Western blot experiments in Molt 4 cells confirmed the interaction in vivo. Preliminary experiments showed that phosphorylation of the catalytic subunit of pol delta by cdk2-cyclins had little or no effect on the specific activity of the enzyme.

[Effect of cGMP on calcium-activated potassium channels in primary cultured porcine coronary artery smooth muscle cells]

Guanosine 3',5'-cyclic monophosphate (cGMP) is capable of relaxing vascular smooth muscle through activating calcium-activated potassium channels (KCa channel) in the vascular smooth muscle cell membrane. But regarding the mechanism it is still under debate. In the present work the mechanism of the effect of cGMP on KCa channel in primary cultured porcine coronary artery smooth muscle cells using patch clamp technique was investigated. Experimental results showed that (1) different concentrations of 8-bromo-cGMP (0.25 mmol/L, 0.50 mmol/L, 1.00 mmol/L), serving as a membrane permeable analogue, could activate KCa channels, and (2) 1.00 mmol/L 8-bromo-cGMP could not activate such kind of channels in inside-out patch under the same condition. These results suggested that the activating effect of cGMP on KCa channels was indirect, being mediated by some intracellular process.

A conserved region in the amino terminus of DNA polymerase delta is involved in proliferating cell nuclear antigen binding

Synthetic peptides to selected sequences in human DNA polymerase delta (pol delta) were used to identify the region involved in the interaction of pol delta to proliferating cell nuclear antigen. Peptides corresponding to sequences in five regions in the amino terminus of human pol delta and three in the carboxyl terminus, which are conserved with the yeast homologs of pol delta, were tested. These studies showed that the peptide corresponding to the N2 region (residues 129-149) selectively and specifically inhibited the PCNA stimulation of pol delta. This inhibition was relieved by titration with excess PCNA. The identification of the N-2 region as being involved in PCNA binding was supported by studies that demonstrated that the N2 peptide could bind PCNA. Deletion mutants of pol delta expressed in Sf9 cells provided evidence that the binding region for PCNA was located in the first 182 residues of the amino terminus. These studies provide reasonable evidence that residues within the region 129-149 of pol delta are involved in the binding site for PCNA.

Regulation of human DNA polymerase delta during the cell cycle

The expression of polymerase delta (pol delta) during the cell cycle was studied in Molt 4 cells separated by counter-flow centrifugal elutriation. Northern blotting showed that pol delta mRNA levels increased by 3-fold at the G1/S border. Levels of pol delta protein determined by Western blotting also peaked at the G1/S border with qualitatively similar changes as the mRNA levels. Thus, pol delta gene expression appears to be regulated during the cell cycle at the transcriptional level. The mRNA half-life for pol delta was determined to be about 8 h and the protein half-life about 10 h. Parallel examination of the expression of proliferating cell nuclear antigen showed that the mRNA levels also increased about 2-fold at the G1/S border, while the protein levels of proliferating cell nuclear antigen increased steadily through the whole cell cycle period, and remained high at G2/M. Analysis of pol alpha expression showed qualitatively similar behavior as pol delta, but the magnitude of the changes were higher. Pulse labeling of cells metabolically arrested in G1,S, or G2/M with 32Pi showed that pol delta is a phosphoprotein and that it is most actively phosphorylated during the S phase.

DNA polymerase delta is involved in the cellular response to UV damage in human cells

We have used antibodies specific for either polymerase delta (pol delta) or its accessory protein, proliferating cell nuclear antigen (PCNA), to demonstrate that they can markedly inhibit the capacity of HeLa nuclear extracts to effect repair of UV-damaged plasmid DNA. This provides the first unambiguous evidence for the involvement of pol delta in DNA repair synthesis. The mRNA levels of both pol delta and PCNA were significantly stimulated subsequent to UV irradiation of cultured cells, providing the first evidence that the cellular response to UV damage may involve regulation of pol delta and PCNA at the gene level. Thus, DNA polymerase delta and its accessory proteins, in addition to their function in replicative DNA synthesis, also function in DNA repair synthesis.

Precancerous gastric lesions in a population at high risk of stomach cancer

A population-based screening for detection of early cancers evaluated the prevalence of precancerous gastric lesions in an area in Shandong province, China, with one of the world's highest rates of stomach cancer. A total of 3433 residents aged 35 to 64 yr received gastroscopical examinations with biopsies taken from standard locations. Chronic atrophic gastritis was nearly universal; less than 2% of the population had biopsies showing entirely normal mucosa or only superficial gastritis. Intestinal metaplasia was the most advanced lesion for 33% and gastric dysplasia for 20%, although the prevalence of each increased significantly with age. Intestinal metaplasia and gastric dysplasia were detected throughout the stomach, but the lesions were more pronounced along the lesser curvature, especially in the angulus and antrum. There was no sex difference in rates of chronic atrophic gastritis, but males had a slightly higher prevalence of intestinal metaplasia, a 1.6-fold increase in dysplasia, and a 3-fold excess of gastric cancer. The data quantify the extensiveness of gastric lesions likely to be involved in the natural history of stomach cancer in this high-risk population.

Serum pepsinogens in relation to precancerous gastric lesions in a population at high risk for gastric cancer

Concentrations of serum pepsinogens (PG) I and II were determined for 3252 randomly selected adults who participated in a population-based gastroscopic screening in an area of China with one of the world's highest rates of gastric cancer. PG I and II concentrations in both sexes tended to be higher than reported in other countries, with levels generally higher among males than females. PG I tended to decrease and PG II to increase with age, but the most pronounced associations were between PG I:II ratios and gastric histology. Median PG I:II ratios monotonically declined from 9.1 to 7.2 to 5.7 to 5.4 to 3.8 among those with superficial gastritis, chronic atrophic gastritis, intestinal metaplasia, dysplasia, and stomach cancer, respectively. The prevalence of dysplasia was nearly 3 times greater among those with PG I:II ratios less than 3 compared with those whose PG I:II ratios were greater than 10. While average levels differed significantly among the histologic groups, the PG I:II ratios were neither sensitive nor specific markers of an individual's likelihood of advanced gastric lesions in this population.

Mechanism of activation of the Ca(2+)-activated K+ channel by cyclic AMP in cultured porcine coronary artery smooth muscle cells

Activation of the Ca(2+)-activated K+ channel (KCa-channel) by adenosine 3', 5'-cyclic monophosphate (cAMP) and cAMP-dependent protein kinase (A-kinase) in cultured smooth muscle cells from porcine coronary artery was investigated using the patch-clamp technique. In cell-attached patches, the KCa-channel was activated when forskolin (10 microM) was applied to the bath. In excised inside-out patches, application of 50 microM cAMP to the bath activated the KCa-channel in the presence of A-kinase (10 units/ml) and ATP (1 mM). In addition, the KCa-channel was activated directly by application of cAMP to the cytoplasmic side of the membrane in the absence of A-kinase. The activation by cAMP or by A-kinase required intracellular Ca2+, and was enhanced by increase of intracellular Ca2+. At a low concentration (3 x 10(-7) M) of Ca2+, more than 2 mM cAMP was required for activation of the KCa-channel, but with 10(-6) M Ca2+, 100 microM cAMP was sufficient for activation. These results suggest that there are two mechanisms of activation of the KCa-channel by cAMP: direct activation, and indirect activation via phosphorylation of the channel by A-kinase.