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Biomedical subjects

Stephen J Hopkins

Publications and source records attributed to Stephen J Hopkins.

13 recordsLinked to original sources
PubMed2006

Variability of the systemic acute phase response after ischemic stroke.

Despite apparent relationships between ischemic stroke and the acute phase response (APR), considerable variation in the APR exists between individuals. We therefore performed post-hoc analysis of individual APR profiles in 31 patients with ischemic stroke in relation to volume of brain infarction. Patients with ischemic stroke had serial blood samples taken within 12 h, and up to 12 months of symptom onset, for analysis of plasma C-reactive protein (CRP) and interleukin-6 (IL-6). Computed tomography (CT) brain infarct volume was measured at 5 to 7 days (median 23.9 cm(3)). An increase in plasma CRP after the admission sample was evident in 94% of patients by day 5 to 7 (median increase 558% of admission value). CRP response, assessed as area under the curve between admission and day 5 to 7, correlated strongly (r=0.62, p<0.001) with CT infarct volume. Those with greater infarct volumes had more evidence of infection, either prior to or during the first week after stroke. The pattern of response was similar for IL-6, although only 77% showed an increase in plasma IL-6 after the admission sample (median increase 148% of admission value). These data suggest that, although infection and other factors may contribute to systemic inflammation, the extent of acute brain injury after ischemic stroke is a major factor influencing the magnitude and variability of the APR.

Acute-Phase Reaction↗
PubMed2006

Comparison of 'real-time' and immunometric RT-PCR: RNA interference of reverse transcriptase-PCR.

We measured interleukin-6 (IL-6) mRNA in whole blood, using an immunometric reverse transcriptase-polymerase chain reaction (IRT-PCR) method and 'real-time' RT-PCR using the Roche LightCycler. Both methods showed similar precision, in terms of inter- and intra-assay variation, where a lower total RNA concentration was used at a relatively high ratio of (IL-6) mRNA to total RNA. However, the 'real-time' RT-PCR method showed a greater loss of accuracy at higher concentrations of total RNA.

Humans↗
PubMed2005

Variability of bacterial translocation in the absence of intestinal mucosal damage following injury and the influence of interleukin-6.

Bacterial translocation and intestinal mucosal damage have been reported as potentially clinically important sequelae of injury. Evidence that endogenous interleukin-6 (IL-6) is able to protect against infection, and that orally administered IL-6 could prevent bacterial translocation and mucosal damage following haemorrhage, led us to evaluate the impact of injury on the intestinal mucosa and the role of endogenous IL-6. Normal and IL-6-deficient (IL-6-/-) mice were subjected to haemorrhage of increasing severity, hind limb ischaemia, or both. Mucosal integrity and bacterial translocation to the liver, spleen and mesenteric lymph nodes (MLN) were examined after 16 h. Bacterial translocation to each of these tissues was observed in unoperated animals. The more severe haemorrhage procedures, and hind limb ischaemia, increased bacterial translocation to the liver significantly in most experiments with normal mice. The IL-6-/- mice survived the most severe haemorrhage procedure less well (p = 0.0015), although increased bacterial translocation was not seen. There was no clear evidence of mucosal damage, or bacterial translocation to spleen and mesenteric lymph nodes, in either normal or IL-6-/- mice. Intestinal IgA concentrations were the same in IL-6-/- mice and controls. These data demonstrate that increased bacterial translocation can be observed following severe injury, but that neither bacterial translocation nor severe injury are inevitably associated with morphological damage to the intestinal mucosa, and endogenous IL-6 is more likely to promote bacterial translocation than protect the gut.

Journal Article↗
PubMed2005

Evaluation of C-reactive protein measurement for assessing the risk and prognosis in ischemic stroke: a statement for health care professionals from the CRP Pooling Project members.

BACKGROUND AND PURPOSE: Several studies have shown, in different populations, that modest elevation of plasma C-reactive protein (CRP) in the range seen in apparently healthy individuals is a strong predictor of future vascular events. Elevated plasma CRP concentrations are also associated with an increased risk of cerebrovascular events and an increased risk of fatal and nonfatal cardiovascular events in ischemic stroke patients. These epidemiological and clinical observations suggest that determination of plasma CRP concentrations could be used as an adjunct for risk assessment in primary and secondary prevention of cerebrovascular disease and be of prognostic value. The aim of this review is to summarize the evidence for CRP as an independent predictor of cerebrovascular events in at-risk individuals and ischemic stroke patients and to consider its usefulness in evaluating prognosis after stroke. SUMMARY OF REVIEW: CRP fulfils most of the requirements of a new risk and prognostic predictor, but several issues await further confirmation and clarification before this marker can be included in the routine evaluation of stroke patients and subjects at risk for cerebrovascular disease. Potentially important associations have been established between elevated plasma CRP concentrations and increased efficacy of established therapies, particularly lipid-lowering therapy with statins. CONCLUSIONS: At present, there is not sufficient evidence to recommend measurement of CRP in the routine evaluation of cerebrovascular disease risk in primary prevention, because there is insufficient evidence as to whether early detection, or intervention based on detection, improves health outcomes, although shared risk of cardiovascular disease indicates this may be of value. In secondary prevention of stroke, elevated CRP adds to existing prognostic markers, but it remains to be established whether specific therapeutic options can be derived from this.

Aged↗
PubMed2004

Peak plasma interleukin-6 and other peripheral markers of inflammation in the first week of ischaemic stroke correlate with brain infarct volume, stroke severity and long-term outcome.

BACKGROUND: Cerebral ischaemia initiates an inflammatory response in the brain and periphery. We assessed the relationship between peak values of plasma interleukin-6 (IL-6) in the first week after ischaemic stroke, with measures of stroke severity and outcome. METHODS: Thirty-seven patients with ischaemic stroke were prospectively recruited. Plasma IL-6, and other markers of peripheral inflammation, were measured at pre-determined timepoints in the first week after stroke onset. Primary analyses were the association between peak plasma IL-6 concentration with both modified Rankin score (mRS) at 3 months and computed tomography (CT) brain infarct volume. RESULTS: Peak plasma IL-6 concentration correlated significantly (p < 0.001) with CT brain infarct volume (r = 0.75) and mRS at 3 months (r = 0.72). It correlated similarly with clinical outcome at 12 months or stroke severity. Strong associations were also noted between either peak plasma C-reactive protein (CRP) concentration or white blood cell (WBC) count, and all outcome measures. CONCLUSIONS: These data provide evidence that the magnitude of the peripheral inflammatory response is related to the severity of acute ischaemic stroke, and clinical outcome.

Aged↗
PubMed2003

Simple, quantitative measurement of cytokine gene expression using an immunometric reverse transcriptase-polymerase chain reaction.

We have developed a novel system to quantify mRNA, using a coupled reverse transcriptase-polymerase chain reaction (RT-PCR) with RNA standards and an immunometric optical readout. Biotinylated RT-PCR products were captured onto avidin-coated microplates and hybridised to a dinitrophenol (DNP)-labelled oligonucleotide probe. Enzyme-linked anti-DNP antibodies were used to detect the product via a colorimetric enzyme assay. Unknown mRNA samples were quantified by interpolating the signal on a standard curve generated from dilutions of RNA (cRNA) standards for interleukin-6 (IL-6), tumour necrosis factor-alpha (TNFalpha), IL-1beta and actin mRNA. The assay for IL-6 mRNA was able to discriminate between samples with a two- to fourfold difference in concentration, had an intra-assay coefficient of variation (CV) of 17% and an inter-assay CV of 24%. The method was used to quantify IL-6 mRNA, relative to expression of IL-6 protein and biological activity, in human blood that had been activated by endotoxin. The IL-6 mRNA could be detected 1 h after endotoxin addition and peaked at 4 h. This paralleled the increase in protein production that followed approximately 1 h later.

Cell Line↗
PubMed2003

An early and sustained peripheral inflammatory response in acute ischaemic stroke: relationships with infection and atherosclerosis.

Central nervous system and peripheral inflammation is important in the responses to ischaemic stroke, and may also predispose to its development. We aimed to identify (1) the extent to which a peripheral inflammatory response is activated in patients following acute stroke, and (2) whether there was evidence for preexisting peripheral inflammation. Thirty-six patients with ischaemic stroke within 12 h of onset of symptoms had serial blood samples taken up to 12 months for analysis of markers of inflammation. Thirty-six control subjects, individually matched for age, sex and degree of atherosclerosis, were also studied. Median C-reactive protein (CRP) was elevated, relative to controls (2.08 mg/l), from admission (4.31 mg/l) (p</=0.001) until 3 months (2.90 mg/l) (p</=0.01), the greatest elevation occurring at 5-7 days (17.67 mg/l) (p</=0.001). Elevations were also seen in erythrocyte sedimentation rate (ESR) and white blood cell (WBC) count until 3 months. Median plasma IL-6 was also elevated, relative to controls (9 pg/ml), by 24 h after onset of symptoms (22 pg/ml) (p</=0.01), and remained elevated at 5-7 days (23 pg/ml) (p</=0.01), but not at 3 months. Less marked elevations in these markers were seen in patients without evidence of infection except for IL-6, which was not increased in the absence of infection. These data provide evidence of an early and sustained peripheral inflammatory response to acute ischaemic stroke in patients with or without evidence of infection. The very early increase in concentrations of inflammatory markers after stroke may either be induced by stroke itself, or may indicate a preexisting inflammatory condition in stroke patients which may contribute to the development of stroke.

Acute Disease↗
PubMed2003

Interleukin-6 is an afferent signal to the hypothalamo-pituitary-adrenal axis during local inflammation in mice.

The cytokines IL-1 and IL-6 are able to induce prostaglandin (PG)-dependent activation of the hypothalamo-pituitary-adrenal axis (HPAA) and are thought to play key roles in immune-neuroendocrine interactions during inflammation. The present study shows that inflammation induced by im injection of turpentine (TPS) in the hind limb of mice causes an increase in the plasma concentration of IL-6, but not that of IL-1 alpha or IL-1 beta, together with a prolonged (>18-h) activation of the HPAA. IL-6 plays a causal role in the TPS-induced elevation in HPAA activity, because the sustained (8-18 h) increases in 1) plasma corticosterone, 2) plasma ACTH, and 3) induction of c-Fos in the hypothalamic paraventricular nucleus are all markedly blunted in IL-6-deficient (IL-6(-/-)) mice. Peripheral administration of a neutralizing IL-6 antiserum inhibited the plasma corticosterone response of normal (C57BL/6) mice to hind limb inflammation to an extent similar to that seen in IL-6(-/-) mice, suggesting that the IL-6 responsible for the increased HPAA activity is produced, or acts, on the blood side of the blood-brain barrier. We also show that IL-6 in the circulation is induced almost exclusively at the local inflammatory site, where IL-1 beta is produced. Induction of IL-6 and activation of the HPAA are dependent upon prior activation of an IL-1 type I receptor, as both are inhibited in type I IL-1 receptor-deficient mice. Furthermore, hind limb inflammation induced cyclooxygenase-2 protein expression around the cerebrovasculature of normal (IL-6(+/+)), but not IL-6(-/-), mice. Based on these data, we propose that IL-6 is produced at the local inflammatory site under the control of IL-1 beta and is the circulating afferent signal that is in part responsible for elevated HPAA activity, possibly acting via eicosanoid production within the cerebrovasculature.

Animals↗
PubMed2002

Euglycemic hyperinsulinemia augments the cytokine and endocrine responses to endotoxin in humans.

Type 2 diabetes is associated with biochemical evidence of low-grade inflammation, and experimental studies have suggested that both insulin and glucose affect inflammatory responses. To determine the effect of in vivo changes in glucose availability and plasma insulin concentrations in humans, we administered 20 U/kg Escherichia coli lipopolysaccharide (LPS) or saline (control) to 14 subjects during a euglycemic hyperinsulinemic clamp (n = 6) or an infusion of sterile saline (n = 8). Parallel in vitro studies on human whole blood were undertaken to determine whether there was a direct effect of glucose, insulin, and leptin on proinflammatory cytokine production. Infusion of glucose and insulin significantly amplified and/or prolonged the cardiovascular, plasma interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and counterregulatory hormone responses to LPS, whereas the effects on fever, plasma norepinephrine concentrations, and oxygen consumption were unaffected. In vitro studies showed no modulation of LPS-stimulated IL-6 or TNF-alpha production by glucose, insulin, or leptin at physiologically relevant concentrations. Hyperinsulinemia indirectly enhances key components of the systemic inflammatory and stress responses in this human model of infection.

Adult↗
PubMed2002

Different photoperiods affect proliferation of lymphocytes but not expression of cellular, humoral, or innate immunity in hamsters.

In seasonal mammals, photoperiod change is associated with a suite of alterations in physiology. It has recently been proposed that the immune response is one of the systems regulated by changes in photoperiod, although this hypothesis has not been rigorously challenged by assays of functional immune responses. The aim of this study was to test the hypothesis that photoperiod modulates immune responsiveness in Syrian (Mesocricetus auratus) and Siberian (Phodopus sungorus) hamsters. Consistent with previously reported data, short-day-housed (SD) animals exhibited a significant increase in lymph node cell (LNC) numbers and increased cellular proliferation in response to the polyclonal mitogen concanavalin A compared to long-day-housed (LD) animals. In contrast, LNC numbers from intact or gonadectomized SD animals that had been sensitized with the antigen dinitrofluorobenzene (DNFB) exhibited a reduced ex vivo proliferative response and reduced production of interleukin-6 (IL-6) compared to LD animals. In vivo studies of the contact hypersensitivity response of animals that had previously been sensitized, and subsequently challenged, with DNFB were similar in SD and LD animals, as was the proliferative activity of LNC recovered from these animals. There were also no photoperiodic differences in the antidinitrophenyl antibody response of animals sensitized with DNFB, or the anti-sheep red blood cell (srbc) response of animals immunized with srbc. Furthermore, no differences could be detected in the activity of natural killer cells from spleens of LD and SD Siberian hamsters, or in lipopolysaccharide-induced IL-6 production by LD and SD Syrian hamsters in vivo. Thus, although photoperiod is able to influence factors regulating the gross number and non-antigen-specific proliferation of lymphocytes in seasonally breeding mammals, day length does not directly influence activation of an effective immune response. The authors conclude, therefore, that expression of the immune response is not directly modified or compromised by photoperiod in these seasonally breeding hamster species.

Animals↗
PubMed2001

Circulating tumour necrosis factor-alpha and interferon-gamma are detectable during acute and convalescent parvovirus B19 infection and are associated with prolonged and chronic fatigue.

To investigate whether cytokine responses may have a bearing on the symptoms and outcome of parvovirus B19 infection, circulating cytokines were measured during acute infection (n=51), follow-up of acute infection (n=39) and in normal healthy controls (n=50). At acute B19 virus infection (serum anti-B19 IgM-positive), patients ranged in age from 4 to 54 years, with a mean age of 28.2 years. The male:female ratio was 1:4.1 and symptoms were rash (n=15), arthralgia (n=31), fatigue (n=8), lymphadenopathy (n=4), foetal hydrops (n=3), transient aplastic crisis (n=2), neutropenia (n=2), myelodysplasia (n=1), thrombocytopenia (n=1) and pancytopenia (n=1). Of these patients, 39 were contacted after a follow-up period of 2-37 months (mean of 22.5 months). In comparison with normal controls, detectable IL-6 was associated with acute B19 virus infection (26%; P=0.0003), but not with follow-up (6%; P=0.16). Detection of interferon (IFN)-gamma was associated with acute B19 virus infection (67%; P<0.0001) and follow-up (67%; P<0.0001). Detection of tumour necrosis factor (TNF)-alpha was associated with acute B19 virus infection (49%; P<0.0001) and follow-up (56%; P<0.0001). IL-1beta was detected in acute infection (20%), but not at follow-up. At acute B19 virus infection, detection of serum/plasma IL-6 was associated with rheumatoid factor (P=0.038) and IFN-gamma (> or =7 pg/ml) was associated with fatigue in those patients of > or =15 years of age (P=0.022). At follow-up, fatigue was associated with IFN-gamma (> or =7 pg/ml) and/or TNF-alpha (> or =40 pg/ml) (P=0.0275). Prolonged upregulation of serum IFN-gamma and TNF-alpha appears to represent a consistent host response to symptomatic B19 virus infection.

Acute Disease↗