Ingegerd Söderström

Up-regulation of cytokines and chemokines predates the onset of rheumatoid arthritis

OBJECTIVE To identify whether cytokines, cytokine-related factors, and chemokines are up-regulated prior to the development of rheumatoid arthritis (RA). METHODS A nested case-control study was performed in 86 individuals who had donated blood samples before experiencing any symptoms of disease (pre-patients) and 256 matched control subjects (1:3 ratio). In 69 of the pre-patients, blood samples were also obtained at the time of the diagnosis of RA. The plasma levels of 30 cytokines, related factors, and chemokines were measured using a multiplex system. RESULTS The levels of several of the cytokines, cytokine receptors, and chemokines were significantly increased in individuals before disease onset compared with the levels in control subjects; i.e., those representing signs of general immune activation (interleukin-1beta [IL-1beta], IL-2, IL-6, IL-1 receptor antagonist, and tumor necrosis factor), activation of Th1 cells (interferon-gamma, IL-12), Th2 cells (IL-4, eotaxin), Treg cells (IL-10), bone marrow-derived factors (IL-7, granulocyte-macrophage colony-stimulating factor, and granulocyte colony-stimulating factor), as well as chemokines (monocyte chemotactic protein 1 and macrophage inflammatory protein 1alpha). The levels were particularly increased in anti-cyclic citrullinated peptide antibody- and rheumatoid factor-positive individuals, and the concentration of most of these increased further after disease onset. The concentration of IL-17 in individuals before disease onset was significantly higher than that in patients after disease onset. Individuals in whom RA subsequently developed were discriminated from control subjects mainly by the presence of Th1 cells, Th2 cells, and Treg cell-related cytokines, while chemokines, stromal cell-derived cytokines, and angiogenic-related markers separated patients after the development of RA from individuals before the onset of RA. CONCLUSION Individuals in whom RA later developed had significantly increased levels of several cytokines, cytokine-related factors, and chemokines representing the adaptive immune system (Th1, Th2, and Treg cell-related factors); after disease onset, the involvement and activation of the immune system was more general and widespread.

Environmental enrichment reverses learning impairment in the Morris water maze after focal cerebral ischemia in rats

Cognitive impairment is common after ischemic stroke. In rodent stroke models using occlusion of the middle cerebral artery (MCA) this is reflected by impaired spatial memory associated with the size of the ischemic lesion. Housing in an enriched environment enhances brain plasticity and improves recovery of sensorimotor functions after experimental stroke in rats. In this study we report that postischemic housing in an enriched environment also attenuates the long‐term spatial memory impairment after MCA occlusion and extinguishes the association between spatial memory and infarct volume. An enriched environment did not significantly alter the expression of selected neuronal plasticity‐associated genes 1 month after MCA occlusion, indicating that most of the adaptive changes induced by an enriched environment have already occurred at this time point. We conclude that the attenuated memory impairment induced by environmental enrichment after MCA occlusion provides a useful model for further studies on the neurobiological mechanisms of recovery of cognitive functions after ischemic stroke.

Mineralocorticoid receptor expression and increased survival following neuronal injury.

Glucocorticoids, acting via the mineralocorticoid receptor, are required for granule neuronal survival in the rat dentate gyrus. Whether this mineralocorticoid receptor‐mediated neuroprotective effect has more general applicability is unknown. Here we report increased mineralocorticoid receptor expression in rat hippocampal and cortical neurons exposed in vitro to low levels of staurosporine and in rat hippocampal pyramidal neurons exposed in vivo to hypothermic transient global ischaemia. In both the cell culture system and the in vivo system increased mineralocorticoid receptor expression is associated with increased neuronal survival, and this increase is reversed by mineralocorticoid receptor antagonism. Modulation of mineralocorticoid receptor gene expression may therefore be an important target for reduction of brain injury in conditions caused by cerebral ischaemia including brain damage following cardiac arrest and stroke.

The association of interleukin-18 genotype and serum levels with metabolic risk factors for cardiovascular disease.

OBJECTIVE Circulating levels of interleukin (IL)-18 are associated with the metabolic syndrome and risk for the development of cardiovascular disease (CVD). This study investigated the association between the circulating IL-18 levels and the -137 G/C polymorphism within the IL-18 gene with metabolic risk factors for CVD in normal-weight and obese black South African women. METHODS Blood pressure (BP), body composition (dual-energy X-ray absorptiometer), visceral adiposity (computerized tomography), as well as fasting glucose, insulin, lipid profile, IL-18 levels, and IL-18 genotype were measured in 104 normal-weight (body mass index (BMI) < or = 25 kg/m2) and 124 obese (BMI > or = 30 kg/m2) black South African women. RESULTS Subjects with a GC genotype (23%) had a greater mean arterial pressure (MAP, 90.6+/-11.1 vs 85.5+/-10.3 mmHg, P<0.001) than the subjects with the GG genotype. Serum IL-18 levels were not associated with IL-18 genotype (P=0.985); however, they significantly correlated with percentage of body fat (r=0.25, P<0.001), visceral adiposity (r=0.32, P<0.001), MAP (r=0.22, P=0.001), HOMA-IR (r=0.33, P<0.001), fasting insulin (r=0.25, P<0.001), triglyceride (r=0.16, P<0.05), and high-density lipoprotein-cholesterol (r=-0.14, P<0.05) levels, after adjusting for age and body fatness. CONCLUSIONS We show for the first time that the GC genotype of the IL-18 -137 G/C polymorphism and the circulating IL-18 levels are independently associated with raised BP. Moreover, fasting IL-18 levels are associated with the other metabolic risk factors for CVD in normal-weight and obese black South African women.

Hyperinsulinemia Enhances Hepatic Expression of the Fatty Acid Transporter Cd36 and Provokes Hepatosteatosis and Hepatic Insulin Resistance

Background: Enhanced hepatic expression of the fatty acid transporter Cd36 correlates with liver fat accumulation, hepatosteatosis, insulin resistance, and hyperinsulinemia. Results: Insulin increases hepatic Cd36 expression in a Pparγ-dependent manner. Conclusion: Hyperinsulinemia stimulates hepatic Cd36 expression, which correlates with the development of hepatosteatosis, hepatic insulin resistance, and dysglycemia. Significance: Hyperinsulinemia contributes to the development of hepatosteatosis and insulin resistance. Hepatosteatosis is associated with the development of both hepatic insulin resistance and Type 2 diabetes. Hepatic expression of Cd36, a fatty acid transporter, is enhanced in obese and diabetic murine models and human nonalcoholic fatty liver disease, and thus it correlates with hyperinsulinemia, steatosis, and insulin resistance. Here, we have explored the effect of hyperinsulinemia on hepatic Cd36 expression, development of hepatosteatosis, insulin resistance, and dysglycemia. A 3-week sucrose-enriched diet was sufficient to provoke hyperinsulinemia, hepatosteatosis, hepatic insulin resistance, and dysglycemia in CBA/J mice. The development of hepatic steatosis and insulin resistance in CBA/J mice on a sucrose-enriched diet was paralleled by increased hepatic expression of the transcription factor Pparγ and its target gene Cd36 whereas that of genes implicated in lipogenesis, fatty acid oxidation, and VLDL secretion was unaltered. Additionally, we demonstrate that insulin, in a Pparγ-dependent manner, is sufficient to directly increase Cd36 expression in perfused livers and isolated hepatocytes. Mouse strains that display low insulin levels, i.e. C57BL6/J, and/or lack hepatic Pparγ, i.e. C3H/HeN, do not develop hepatic steatosis, insulin resistance, or dysglycemia on a sucrose-enriched diet, suggesting that elevated insulin levels, via enhanced CD36 expression, provoke fatty liver development that in turn leads to hepatic insulin resistance and dysglycemia. Thus, our data provide evidence for a direct role for hyperinsulinemia in stimulating hepatic Cd36 expression and thus the development of hepatosteatosis, hepatic insulin resistance, and dysglycemia.

Depot- and ethnic-specific differences in the relationship between adipose tissue inflammation and insulin sensitivity

Objective  It is unclear whether there are differences in inflammatory gene expression between abdominal and gluteal subcutaneous adipose tissue (SAT), and between black and white women. We therefore tested the hypotheses that SAT inflammatory gene expression is greater in the abdominal compared to the gluteal depot, and SAT inflammatory gene expression is associated with differential insulin sensitivity (SI) in black and white women.

Estrogen Reduces 11β-Hydroxysteroid Dehydrogenase Type 1 in Liver and Visceral, but Not Subcutaneous, Adipose Tissue in Rats

Following menopause, body fat is redistributed from peripheral to central depots. This may be linked to the age related decrease in estrogen levels. We hypothesized that estrogen supplementation could counteract this fat redistribution through tissue‐specific modulation of glucocorticoid exposure. We measured fat depot masses and the expression and activity of the glucocorticoid‐activating enzyme 11β‐hydroxysteroid dehydrogenase type 1 (11βHSD1) in fat and liver of ovariectomized female rats treated with or without 17β‐estradiol. 11βHSD1 converts inert cortisone, or 11‐dehydrocorticosterone in rats into active cortisol and corticosterone. Estradiol‐treated rats gained less weight and had significantly lower visceral adipose tissue weight than nontreated rats (P < 0.01); subcutaneous adipose weight was unaltered. In addition, 11βHSD1 activity/expression was downregulated in liver and visceral, but not subcutaneous, fat of estradiol‐treated rats (P < 0.001 for both). This downregulation altered the balance of 11βHSD1 expression and activity between adipose tissue depots, with higher levels in subcutaneous than visceral adipose tissue of estradiol‐treated animals (P < 0.05 for both), opposite the pattern in ovariectomized rats not treated with estradiol (P < 0.001 for mRNA expression). Thus, estrogen modulates fat distribution, at least in part, through effects on tissue‐specific glucocorticoid metabolism, suggesting that estrogen replacement therapy could influence obesity related morbidity in postmenopausal women.

The relationship between the val158met catechol-O-methyltransferase (COMT) polymorphism and irritable bowel syndrome.

Background The catechol-O-methyltransferase (COMT) enzyme has a key function in the degradation of catecholamines and a functional polymorphism is val158met. The val/val genotype results in a three to fourfold higher enzymatic activity compared with the met/met genotype, with the val/met genotype exhibiting intermediate activity. Since pain syndromes as well as anxiety and depression are associated to low and high COMT activity respectively and these conditions are all associated with irritable bowel syndrome (IBS) we wanted for the first time to explore the relationship between the polymorphism and IBS. Methodology/Principal Findings 867 subjects (445 women) representative of the general population and 70 consecutively sampled patients with IBS (61 women) were genotyped for the val158met polymorphism and the IBS patients filled out the Hospital-Anxiety-and-Depression-Scale (HADS) questionnaire, and an IBS symptom diary. Results There was a significantly higher occurrence of the val/val genotype in patients compared with controls (30% vs 20%; Chi2 (1) 3.98; p = 0.046) and a trend toward a lower occurrence of the val/met genotype in IBS patients compared with controls (39% vs 49%; Chi2 (1) 2.89; p = 0.089). Within the IBS patients the val/val carriers exhibited significantly increased bowel frequency (2.6 vs 1.8 stools per day; Chi2 (1) 5.3; p = 0.03) and a smaller proportion of stools with incomplete defecation (41% vs 68%; Chi2 (1) 4.3; p = 0.04) compared with the rest (val/met+met/met carriers). The val/val carriers also showed a trend for a smaller proportion of hard stools (0% vs 15%; Chi2 (1) 3.2; p = 0.08) and a higher frequency of postprandial defecation (26% vs 21%; Chi2 (1) 3.0; p = 0.08). Conclusions/Significance In this study we found an association between the val/val genotype of the val158met COMT gene and IBS as well as to specific IBS related bowel pattern in IBS patients.

17β-estradiol and enriched environment accelerate cognitive recovery after focal brain ischemia

Cognitive impairments, including spatial memory and learning deficiencies, are common after ischemic stroke. Estrogen substitution improves cognitive functions in post‐menopausal women and ovariectomized rodents, partially through induction of neuroplasticity in the hippocampal formation. Post‐ischemic housing of male rats in an enriched environment (EE) improves functional outcome, without changing infarct volume. We hypothesized that 17β‐estradiol combined with an EE would accelerate cognitive recovery after focal brain ischemia in ovariectomized rats and that recovery would be related to altered expression of nerve growth factor‐induced gene (NGFI)‐A in the hippocampus. 17β‐estradiol or placebo pellets were implanted 6 h after transient middle cerebral artery occlusion. Two days later, rats were placed in an EE or a deprived environment (DE) for 6 weeks. At 5 weeks after middle cerebral artery occlusion, 17β‐estradiol‐treated rats housed in an EE showed improvements in cognitive function (i.e. shorter latency and path in the Morris water maze task) compared with placebo‐treated animals housed in an EE. Furthermore, beneficial effects on latency and path were observed when comparing EE‐housed vs. DE‐housed 17β‐estradiol‐treated rats. When comparing 17β‐estradiol‐treated EE‐housed rats vs. placebo‐treated DE‐housed rats, pronounced effects on latency and path were observed. Infarct volumes did not differ between groups. 17β‐estradiol‐treated EE‐housed rats had significantly higher NGFI‐A mRNA expression bilaterally in the cornu ammonis 1 region and in the ipsilateral dentate gyrus of the hippocampus, compared with placebo‐treated EE‐housed rats. In conclusion, 17β‐estradiol treatment combined with an EE improved recovery of cognitive function after experimental brain ischemia, putatively through the upregulation of NGFI‐A in hippocampal subregions.

Establishment and Characterization of RAG-2 Deficient Non-Obese Diabetic Mice

The authors have established a new immunodeficient mouse strain on the genetic background of the diabetes prone non‐obese diabetic (NOD) mouse. A deletion mutant of the RAG‐2 gene was back crossed 10 generations onto the NOD/Bom strain background. The homozygous NODrag−2−/− mice lack functionally mature B and T lymphocytes and do not develop insulitis or diabetes throughout life. In contrast, heterozygous NODrag−2+/− develop both insulitis and diabetes with an incidence similar to the wild type NOD mice. In transfer experiments, spleen cells from diabetic NOD donors were found to transfer disease to NODrag−2−/− recipients similar to what has been previously observed in transfer to irradiated NOD recipients or to immunodeficient NOD‐scid/scid mice. While resembling the recently established NOD‐scid/scid mice in many respects, the NODrag−2−/− mice represents an advantageous model for reconstitution of the pathogenesis of murine IDDM as it does not produce any endogenous, mature T or B lymphocytes.