Glucocorticoids and oxidative stress

Resolution of neutrophilic inflammation by H2O2 in antigen-induced arthritis

OBJECTIVE

Neutrophil accumulation contributes to the pathogenesis of rheumatoid arthritis. This study was undertaken to examine the ability of H2O2 to influence neutrophilic inflammation in a model of antigen-induced arthritis (AIA) in mice.

METHODS

AIA was induced by administration of antigen into the knee joints of previously immunized mice. Neutrophil accumulation was measured by counting neutrophils in the synovial cavity and assaying myeloperoxidase activity in the tissue surrounding the mouse knee joint. Apoptosis was determined by morphologic and molecular techniques. The role of H2O2 was studied using mice that do not produce reactive oxygen species (gp91phox-/- mice) and drugs that enhance the generation or enhance the degradation of H2O2.

RESULTS

Antigen challenge of immunized mice induced neutrophil accumulation that peaked at 12-24 hours after challenge. H2O2 production peaked at 24 hours, after which time, the inflammation resolved. Neutrophil recruitment was similar in wild-type and gp91phox-/- mice, but there was delayed resolution in gp91phox-/- mice or after administration of catalase. In contrast, administration of H2O2 or superoxide dismutase (SOD) resolved neutrophilic inflammation. The resolution of inflammation induced by SOD or H2O2 was accompanied by an increase in the number of apoptotic neutrophils. Apoptosis was associated with an increase in Bax and caspase 3 cleavage and was secondary to phosphatidylinositol 3-kinase (PI3K)/Akt activation.

CONCLUSION

Our findings indicate that levels of H2O2 increase during neutrophil influx and are necessary for the natural resolution of neutrophilic inflammation. Mechanistically, enhanced levels of H2O2 (endogenous or exogenous) inhibit p-Akt/NF-κB and induce apoptosis of migrated neutrophils. Modulation of H2O2 production may represent a novel strategy for controlling neutrophilic inflammation in the joints.

Knockout of the vascular endothelial glucocorticoid receptor abrogates dexamethasone-induced hypertension

BACKGROUND

Glucocorticoid-mediated hypertension is incompletely understood. Recent studies have suggested the primary mechanism of this form of hypertension may be through the effects of glucocorticoids on vascular tissues and not to excess sodium and water re-absorption as traditionally believed.

OBJECTIVE

The goal of this study was to better understand the role of the vasculature in the generation and maintenance of glucocorticoid-mediated hypertension.

METHODS

We created a mouse model with a tissue-specific knockout of the glucocorticoid receptor in the vascular endothelium.

RESULTS

We show that these mice are relatively resistant to dexamethasone-induced hypertension. After 1 week of dexamethasone treatment, control animals have a mean blood pressure (BP) increase of 13.1 mmHg, whereas knockout animals have only a 2.7 mmHg increase (P < 0.001). Interestingly, the knockout mice have slightly elevated baseline BP compared with the controls (112.2 ± 2.5 vs. 104.6 ± 1.2 mmHg, P = 0.04), a finding which is not entirely explained by our data. Furthermore, we demonstrate that the knockout resistance arterioles have a decreased contractile response to dexamethasone with only 6.6% contraction in knockout vessels compared with 13.4% contraction in control vessels (P = 0.034). Finally, we show that in contrast to control animals, the knockout animals are able to recover a significant portion of their normal circadian BP rhythm, suggesting that the vascular endothelial glucocorticoid receptor may function as a peripheral circadian clock.

CONCLUSION

Our study highlights the importance of the vascular endothelial glucocorticoid receptor in several fundamental physiologic processes, namely BP homeostasis and circadian rhythm.

Blood Pressure and Left Ventricular Characteristics in Young Patients with Classical Congenital Adrenal Hyperplasia due to 21-Hydroxylase Deficiency

High steroid doses are often necessary in congenital adrenal hyperplasia (CAH) to suppress androgens and may increase blood pressure (BP). We evaluated 24-hour BP profile (ambBP), BP during exercise (excBP), and echocardiography in 20 young CAH patients. Systolic and diastolic BP during ambBP and excBP was normal in all patients. None presented myocardial hypertrophy. Nocturnal diastolic BP was affected by testosterone (P: .016, 95% CI: 0.002 to 0.021, β = 0.01). Left ventricular mass (LVM ) was affected by height SDS (P: .007, 95% CI: 2.67 to 14.17, β = 8.42), age (P: < .0001, 95% CI: 2.12 to 5.82, β = 3.97), and testosterone (P: .008, 95% CI: 0.01 to 0.09, β = 0.053). Left ventricular mass index (LVMI) correlated with BMI SDS (P: .044, 95% CI: 0.09 to 6.17, β = 3.13) and testosterone (P: .031, 95% CI: 0.002 to 0.035, β = 0.018). Hydrocortisone dose did not influence ambBP, excBP, or myocardial hypertrophy.

The effect of polyphenol-rich dark chocolate on fasting capillary whole blood glucose, total cholesterol, blood pressure and glucocorticoids in healthy overweight and obese subjects

Numerous studies indicate that polyphenol-rich chocolate reduces fasting blood glucose, blood pressure (BP) and total cholesterol in healthy individuals and hypertensives with or without glucose intolerance. The aim of the present study was to investigate the effect of two doses of polyphenol-rich dark chocolate (DC) on fasting capillary whole blood glucose, total cholesterol and BP and to examine whether improvements in these parameters are associated with changes in adrenocorticoid excretion in overweight and obese individuals. The study used a randomised, single-blind, cross-over design where fourteen overweight and obese subjects were randomised to either take 20 g DC with 500 mg polyphenols then 20 g DC with 1000 mg polyphenols or vice-versa. Participants followed each diet for 2 weeks separated by a 1-week washout period. It was observed that the 500 mg polyphenol dose was equally effective in reducing fasting blood glucose levels, systolic BP (SBP) and diastolic BP (DBP) as the 1000 mg polyphenol dose suggesting that a saturation effect might occur with increasing dose of polyphenols. There was also a trend towards a reduction in urinary free cortisone levels with both groups although it did not reach statistical significance. No changes in anthropometrical measurements were seen. We suggest that more research is required to investigate the mechanism(s) by which polyphenol-rich foods influence health.

Inverse association of cortisol serum levels with T-tau, P-tau 181 and P-tau 231 peptide levels and T-tau/Abeta 1-42 ratios in CSF in patients with mild Alzheimer's disease dementia

Hypercortisolemia and increased levels of hyperphosphorylated tau proteins in cerebrospinal fluid (CSF) are common features with pathogenic relevance in Alzheimer;s disease (AD). Experimental studies point to an influence of cortisol on Abeta and tau pathology in AD. Association of both parameters have not yet been described in a sample of AD patients. In the present study, serum levels of cortisol were determined in 26 patients with mild AD dementia and 20 age-matched healthy elderly controls by ELISA. In addition, we measured in AD patients CSF levels of cortisol, total tau (T-tau), tau phosphorylated at threonine 181 (P-tau 181), tau protein phosphorylated at threonine 231 (P-tau 231) and beta-Amyloid (Abeta) 1-42 and determined T-tau/Abeta 1-42 ratios in CSF. We found in AD patients significantly increased cortisol serum levels (551.4 +/- 146.1 nmol/l; P = 0.002) as compared to healthy controls (435.3 +/- 83.9 nmol/l). In AD patients, cortisol serum levels were significantly inversely correlated with T-tau (r = -0.496; P = 0.01), P-tau 181 (r = -0.558; P = 0.003) and P-tau 231 (-0.500; P = 0.009) protein levels and T-tau/Abeta 1-42 ratios (r = -0.450; P = 0.021) in CSF. In addition, cortisol serum levels showed a trend of positive correlation with Abeta 1-42 CSF levels (r = 0.386; P = 0.052). However, no significant correlations of cortisol serum with CSF levels as well as cortisol CSF levels with CSF biomarkers could be detected in AD patients. In conclusion, our results show that increased cortisol serum but not CSF levels are associated with minor signs of AD pathology in CSF, indicating a putative neuroprotective effect of moderately elevated cortisol serum levels in patients with mild AD dementia.