Alveolar macrophages and emphysema in surfactant protein-D-deficient mice

Abstract:   Surfactant protein-D (SP-D) is a member of the collectin family of collagenous proteins with lectin activity. SP-D is expressed in numerous tissues, primarily in type II alveolar cells in the periphery of the lung. SP-D plays an important role in host defense of the lung. To evaluate the importance of SP-D in vivo , transgenic mice lacking SP-D (SP-D-/- mice) have been generated. Lipid accumulation and airspace enlargement were observed in the lungs of SP-D-/- mice within 3 weeks after birth, and progressed with advancing age. Airspace enlargement and abnormalities in elastin fibers supported the concept that SP-D was required to inhibit destruction of the alveoli. Alveolar macrophages from SP-D-/- mice produced more H₂O₂ and matrix metalloproteinases (MMP)-2, -9, and -12 compared with wild-type mice. In vitro studies demonstrated that oxidants derived in part from NADPH oxidase enhanced NF-κB activation and MMP production in alveolar macrophages from SP-D-/- mice. A specific inhibitor of NF-κB reduced MMP production by alveolar macrophages from SP-D-/- mice. Taken together, these data demonstrated oxidant-dependent activation of NF-κB and enhanced MMP expression by alveolar macrophages from SP-D-/- mice, a process likely to mediate airspace remodeling caused by SP-D deficiency. SP-D plays a critical role in regulating alveolar macrophage activation, oxidant production, and MMP activity that may influence the pathogenesis of various pulmonary disorders.     

The critical role of hematopoietic cells in lipopolysaccharide-induced airway inflammation

Rapid and selective recruitment of neutrophils into the airspace in response to LPS facilitates the clearance of bacterial pathogens. However, neutrophil infiltration can also participate in the development and progression of environmental airway disease. Previous data have revealed that Toll-like receptor 4 (tlr4) is required for neutrophil recruitment to the lung after either inhaled or systemically administrated LPS from Escherichia coli. Although many cell types express tlr4, endothelial cell expression of tlr4 is specifically required to sequester neutrophils in the lung in response to systemic endotoxin. To identify the cell types requiring trl4 expression for neutrophil recruitment after inhaled LPS, we generated chimeric mice separately expressing tlr4 on either hematopoietic cells or on structural lung cells. Neutrophil recruitment into the airspace was completely restored in tlr4-deficient mice receiving wild-type bone marrow. By contrast, wild-type animals receiving tlr4-deficient marrow had dramatically reduced neutrophil recruitment. Moreover, adoptive transfer of wild-type alveolar macrophages also restored the ability of tlr4-deficient recipient mice to recruit neutrophils to the lung. These data demonstrate the critical role of hematopoietic cells and alveolar macrophages in initiating LPS-induced neutrophil recruitment from the vascular space to the airspace.     

Sex differences in response to steroids in preterm sheep lungs are not explained by glucocorticoid receptor number or binding affinity.

We recently reported that prenatal glucocorticoid therapy is less effective at promoting an improvement in lung function in male than in female sheep. This observation, and the higher incidence of respiratory distress syndrome in human males, suggests that the male fetal lung may be less responsive to glucocorticoids than is the female fetal lung. Since glucocorticoids are known to exert their effects via specific cytoplasmic glucocorticoid receptors (GR), we hypothesized that there may be sexual dimorphism in either the number or binding affinity of lung GR. To test the hypothesis, binding of dexamethasone (a synthetic glucocorticoid, 0.5-40 nM) by cytosolic fractions of male (n = 16) and female (n = 16) fetal sheep lung was measured at 125 days gestation (term = 148 days). Scatchard analysis of dexamethasone binding showed that the total number of GR (Bmax) did not significantly differ between male (346 +/- 42 fmol/mg protein) and female (277 +/- 23 fmol/mg protein) fetuses. The measured binding affinity (Kd) in male fetal lungs (6.85 +/- 0.43 nM) was not significantly different from that in females (8.46 +/- 1.02 nM). In conclusion, this study suggests that sex differences in fetal sheep lung responses to glucocorticoid therapy are not due to differences in the number or binding affinity of lung GR.     

Upregulation of alveolar epithelial active Na+ transport is dependent on beta2-adrenergic receptor signaling

Alveolar epithelial beta-adrenergic receptor (betaAR) activation accelerates active Na+ transport in lung epithelial cells in vitro and speeds alveolar edema resolution in human lung tissue and normal and injured animal lungs. Whether these receptors are essential for alveolar fluid clearance (AFC) or if other mechanisms are sufficient to regulate active transport is unknown. In this study, we report that mice with no beta1- or beta2-adrenergic receptors (beta1AR-/-/beta2AR-/-) have reduced distal lung Na,K-ATPase function and diminished basal and amiloride-sensitive AFC. Total lung water content in these animals was not different from wild-type controls, suggesting that betaAR signaling may not be required for alveolar fluid homeostasis in uninjured lungs. Comparison of isoproterenol-sensitive AFC in mice with beta1- but not beta2-adrenergic receptors to beta1AR-/-/beta2AR-/- mice indicates that the beta2AR mediates the bulk of beta-adrenergic-sensitive alveolar active Na+ transport. To test the necessity of betaAR signaling in acute lung injury, beta1AR-/-/beta2AR-/-, beta1AR+/+/beta2AR-/-, and beta1AR+/+/beta2AR+/+ mice were exposed to 100% oxygen for up to 204 hours. beta1AR-/-/beta2AR-/- and beta1AR+/+/beta2AR-/- mice had more lung water and worse survival from this form of acute lung injury than wild-type controls. Adenoviral-mediated rescue of beta2-adrenergic receptor (beta2AR) function into the alveolar epithelium of beta1AR-/-/beta2AR-/- and beta1AR+/+/beta2AR-/- mice normalized distal lung beta2AR function, alveolar epithelial active Na+ transport, and survival from hyperoxia. These findings indicate that betaAR signaling may not be necessary for basal AFC, and that beta2AR is essential for the adaptive physiological response needed to clear excess fluid from the alveolar airspace of normal and injured lungs.     

Follistatin-like 1 (Fstl1) is a bone morphogenetic protein (BMP) 4 signaling antagonist in controlling mouse lung development

Lung morphogenesis is a well orchestrated, tightly regulated process through several molecular pathways, including TGF-β/bone morphogenetic protein (BMP) signaling. Alteration of these signaling pathways leads to lung malformation. We investigated the role of Follistatin-like 1 (Fstl1), a secreted follistatin-module-containing glycoprotein, in lung development. Deletion of Fstl1 in mice led to postnatal lethality as a result of respiratory failure. Analysis of the mutant phenotype showed that Fstl1 is essential for tracheal cartilage formation and alveolar maturation. Deletion of the Fstl1 gene resulted in malformed tracheal rings manifested as discontinued rings and reduced ring number. Fstl1-deficient mice displayed septal hypercellularity and end-expiratory atelectasis, which were associated with impaired differentiation of distal alveolar epithelial cells and insufficient production of mature surfactant proteins. Mechanistically, Fstl1 interacted directly with BMP4, negatively regulated BMP4/Smad1/5/8 signaling, and inhibited BMP4-induced surfactant gene expression. Reducing BMP signaling activity by Noggin rescued pulmonary atelectasis of Fstl1-deficient mice. Therefore, we provide in vivo and in vitro evidence to demonstrate that Fstl1 modulates lung development and alveolar maturation, in part, through BMP4 signaling.     

SIRT1减弱对脂多糖致急性呼吸窘迫综合征小鼠的促炎作用

目的探讨SIRT1对脂多糖(LPS)诱导的急性呼吸窘迫综合征(ARDS)小鼠炎症反应的作用及其机制。方法采用SIRT1基因敲减小鼠SIRT1~(+/-)与野生型小鼠,qRT-PCR,Western Blot检测两种小鼠肺组织中的相关基因表达差异。两种小鼠用LPS腹腔注射法造模,同时设生理盐水对照组,观察肺组织病理形态学变化,测定肺湿干比(W/D比),BCA法测定支气管肺泡灌洗液(BALF)中总蛋白浓度,ELISA法测定BALF及血浆中炎症因子TNF-α、IL-6的含量,Western Blot检测肺组织p-p38MAPK、p38MAPK、p-ATF2的表达变化。结果与野生型小鼠相比,SIRT1~(+/-)肺组织中SIRT1在mRNA表达和蛋白表达均显著降低,差异有统计学意义(P0.01)。LPS致ARDS后,两种小鼠病理形态学观察均表现为肺组织炎症细胞浸润,肺泡结构破坏,间质水肿,肺泡间隔增厚,而SIRT1~(+/-)小鼠肺组织破坏更严重。在SIRT1~(+/-)小鼠中,肺W/D比值,BALF中总蛋白浓度,BALF及血浆中炎症因子肿瘤坏死因子-α(TNF-α)、白细胞介素-6(IL-6)的含量,均明显高于野生型小鼠(P0.05),肺组织p-p38MAPK/p38MAPK、p-ATF2的表达增加也更显著(P0.05)。结论 SIRT1基因在LPS致伤ARDS小鼠的炎症进程中起着非常重要的作用,其机制可能与Sirt1诱导的p38 MAPK-p-ATF2信号通路的活化增强有关。     

Circadian rise in maternal glucocorticoid prevents pulmonary dysplasia in fetal mice with adrenal insufficiency

The hypothalamic-pituitary-adrenal (HPA) axis, including hypothalamic corticotropin-releasing hormone (CRH) and pituitary corticotropin, is one of the first endocrine systems to develop during fetal life, probably because glucocorticoid secretion is necessary for the maturation of many essential fetal organs. Consistent with this, pregnant mice with an inactivating mutation in the Crh gene deliver CRH-deficient offspring that die at birth with dysplastic lungs, which can be prevented by prenatal maternal glucocorticoid treatment. But children lacking the ability to synthesize cortisol (because of various genetic defects in adrenal gland development or steroidogenesis) are not born with respiratory insufficiency or abnormal lung development, suggesting that the transfer of maternal glucocorticoid across the placenta might promote fetal organ maturation in the absence of fetal glucocorticoid production. We used pregnant mice with a normal HPA axis carrying fetuses with CRH deficiency to characterize the relative contributions of the fetal and maternal adrenal to the activity of the fetal HPA axis, and related these findings to fetal lung development. We found that in the presence of fetal adrenal insufficiency, normal fetal lung development is maintained by the transfer of maternal glucocorticoid to the fetus, specifically during the circadian peak in maternal glucocorticoid secretion.     

Neonatal exposure to 65% oxygen durably impairs lung architecture and breathing pattern in adult mice

STUDY OBJECTIVE: To test the hypothesis that exposure to hyperoxia during the postnatal period of rapid alveolar multiplication by septation would cause permanent impairments, even with moderate levels of hyperoxia. DESIGN: We exposed mouse pups to 65% O(2) (hyperoxic mice) or normoxia (normoxic mice) during their first postnatal month, and we analyzed lung histology, pulmonary mechanics, blood gas, and breathing pattern during normoxia or in response to chemical stimuli in adulthood, when they reached 7 to 8 months of postnatal age. RESULTS: Hyperoxic mice had fewer and larger alveoli than normoxic mice (number of alveoli per unit surface area of parenchyma, 266 +/- 62/mm(2) vs 578 +/- 77/mm(2), p < 0.0001) [mean +/- SD], the cause being impaired alveolarization (radial alveolar count, 5.8 +/- 0.2 in hyperoxic mice vs 10.5 +/- 0.5 in normoxic mice, p < 0.0001). Respiratory system compliance was higher in hyperoxic mice (0.098 +/- 0.006 mL/cm H(2)O) than in normoxic mice (0.064 +/- 0.006 mL/cm H(2)O, p < 0.016). Baseline tidal volume (VT) and breath duration (TTOT]) measured noninvasively by whole-body plethysmography were larger in hyperoxic mice than in normoxic mice (VT, + 15%, p < 0.01; TTOT, + 12%, p < 0.01). Despite these impairments, blood gas, baseline minute ventilation E, and E responses to hypoxia and hypercapnia were normal in hyperoxic mice, compared with normoxic mice. CONCLUSION: Hyperoxic exposure during lung septation in mice may cause irreversible lung injury and breathing pattern abnormalities in adulthood at O(2) concentrations lower than previously thought. However, ventilatory function and body growth were preserved, and ventilatory function showed no major abnormalities, at least at rest, despite early oxygen-induced injuries.     

Cathepsin K deficiency aggravates lung injury in hyperoxia-exposed newborn mice

Cathepsin K (CatK) is a potent collagenase and elastase and may be involved in the development of neonatal bronchopulmonary dysplasia. The authors evaluated the effects of CatK deletion on neonatal lung development and response to prolonged hyperoxic challenge. CatK deficiency resulted in thinner alveolar walls than wild-type littermates on postnatal day (PN) 7. However, no morphological difference could be detected between CatK-deficient and control groups on PN 14. Exposure to 90% oxygen for 7 days after birth caused intensive CatK expression in the bronchial epithelium and alveolar macrophages of wild-type mice. Hyperoxia caused fatal respiratory distress in both groups of mice. However, whereas ～20% of wild-type mice survived for 2 weeks in hyperoxia, all CatK-deficient mice died within the first 9 postnatal days. Hyperoxia-exposed lungs of CatK-deficient mice contained high number of macrophages and multinucleated giant cells and had increased content of reduced glutathione, indicating intensified pulmonary oxidative stress. These results suggest that CatK is involved in pulmonary development and it may be an important host-defence protease in the oxygen-stressed newborn lung.     

Igf2 deficiency results in delayed lung development at the end of gestation

IGF-II is a polypeptide hormone with structural homology to insulin and IGF-I. IGF-II plays an important role in fetal growth as mice with targeted disruption of the IGF-II gene (Igf2) exhibit severe growth retardation. The role of IGFs in the fetal lung has been suggested by several studies, including those that have identified IGF mRNA expression, and that of their receptors and binding proteins in the lungs at different stages of development. In this study, we used mice carrying a null mutation of Igf2 (Igf2-/- mice) to determine whether the absence of IGF-II had any effect in fetal lung maturation. Our results showed that the lungs of Igf2-/- fetuses had thicker alveolar septae and poorly organized alveoli when compared with those of Igf2+/+ on d 17.5 and 18.5 of gestation. These morphological alterations may be the result of exposure to lower levels of glucocorticoids because plasma corticosterone levels were significantly lower in Igf2-/- mothers compared with wild-type controls. In support of this, fetuses from homozygous knockout matings, where mothers were treated with 15 microg/ml corticosterone, and Igf2-/- fetuses obtained from heterozygous matings had similar lung histology to those of wild-type fetuses. Finally, we found that IGF-I and SP-B mRNA levels were up-regulated in the lungs of Igf2-/- fetuses at the end of gestation. This study suggests that Igf2 plays an important role in the development of the fetal lung and may affect fetal lung maturation by regulating maternal factors, such as corticosterone levels, during pregnancy.     

Decreased hypothalamic and adrenal angiotensin II receptor expression and adrenomedullary catecholamines in transgenic mice with impaired glucocorticoid receptor function

In transgenic mice expressing an antisense mRNA against the glucocorticoid receptor (GR), which partially blocks GR expression, impaired glucocorticoid feedback efficacy is accompanied by reduced hypothalamic corticotropin-releasing hormone (CRH) and vasopressin (AVP) activity and reduced peripheral sympathetic tone, indications of a shift in the balance of hypothalamic CRH and sympathetic regulation. As angiotensin II (Ang II) regulates CRH, AVP and sympathetic activity, we studied the expression of Ang II receptors in the hypothalamus and adrenal gland of GR transgenic and wild-type mice, adrenal catecholamines and mRNA for their rate-limiting enzyme, tyrosine hydroxylase (TH). We found that transgenic mice expressed significantly less numbers of Ang II AT(1) receptors in the hypothalamic paraventricular nucleus and median eminence, lower numbers of AT(2) receptors in supraoptic and paraventricular nuclei and lower numbers of AT(2) receptors in the adrenal medulla when compared with wild-type controls. The expression of TH mRNA and the concentration of adrenomedullary epinephrine and norepinephrine were also lower in transgenic mice when compared with wild-type controls. Decreased hypothalamic and adrenal Ang II receptor stimulation as a result of decreased GR expression may explain the decreased hypothalamic CRH and AVP and decreased adrenomedullary and sympathetic activities in this model.     

Similarities and dissimilarities of branching and septation during lung development

The lungs of small premature babies are at a developmental stage of finalizing their airway tree by a process called branching morphogenesis, and of creating terminal gas exchange units by a mechanism called septation. If the branching process is disturbed, the lung has a propensity to be hypoplastic. If septation is impaired, the terminal gas exchange units, the alveoli, tend to be enlarged and reduced in number, an entity known as bronchopulmonary dysplasia. Here, we review current knowledge of key molecules influencing branching and septation. In particular, we discuss the molecular similarities and dissimilarities between the two processes of airspace enlargement. Understanding of the molecular mechanisms regulating branching and septation may provide perinatologists with targets for improving lung growth and maturation.     

Loss of glucocorticoid receptor function in the pituitary results in early postnatal lethality

Glucocorticoid action in the brain is mediated by the glucocorticoid receptor (GR) and the mineralocorticoid receptor, thereby affecting physiological processes such as neurogenesis, synaptic plasticity, and neuroendocrine control. To examine GR function in the regulation of the hypothalamic-pituitary-adrenal axis, we generated GR mutant mice that are homozygous for a conditional GR allele and heterozygous for a transgene that expresses the Cre recombinase under control of the regulatory elements of the mouse calcium/calmodulin-dependent protein kinase IIalpha gene, resulting in Cre-mediated recombination in the brain and pituitary. The GR mutants die about 1 wk after birth and display a fulminant increase in plasma corticosterone as well as a severe histopathological phenotype. To assess in which time frame targeting of the pituitary occurs during embryonic development, we used a transgenic line expressing an inducible CreER(T2) fusion protein under the control of the regulatory elements of the calcium/calmodulin-dependent protein kinase IIalpha gene. Cre reporter data show that pituitary targeting occurred during embryonic development at the time when glucocorticoid synthesis starts.     

Differential effect of dexamethasone and hydrocortisone on alveolar growth in rat pups

Glucocorticoids are widely used in perinatology, since they decrease the incidence of respiratory distress syndrome and chronic lung disease. However, evidence is now increasing that their use in this age group may result in impaired alveolar lung growth and general development. The aim of this study was to determine whether a low dose of hydrocortisone (1 mg/kg/day for 11 days) was deleterious to lung growth in rat pups, as compared to an equivalent dose of dexamethasone. While both dexamethasone and hydrocortisone increased alveolar diameter with thinning of the interairspace walls, only dexamethasone reduced the overall internal surface area of the lung available for respiratory exchange. Changes were more marked with dexamethasone as compared to hydrocortisone, which did not appear to affect alveolar septation.In conclusion, a prolonged course of low-dose hydrocortisone may be deleterious for alveolar lung growth in rat pups, but the changes are less marked than those caused by dexamethasone.     

Altered stability of pulmonary surfactant in SP-C-deficient mice

The surfactant protein C (SP-C) gene encodes an extremely hydrophobic, 4-kDa peptide produced by alveolar epithelial cells in the lung. To discern the role of SP-C in lung function, SP-C-deficient (-/-) mice were produced. The SP-C (-/-) mice were viable at birth and grew normally to adulthood without apparent pulmonary abnormalities. SP-C mRNA was not detected in the lungs of SP-C (-/-) mice, nor was mature SP-C protein detected by Western blot of alveolar lavage from SP-C (-/-) mice. The levels of the other surfactant proteins (A, B, D) in alveolar lavage were comparable to those in wild-type mice. Surfactant pool sizes, surfactant synthesis, and lung morphology were similar in SP-C (-/-) and SP-C (+/+) mice. Lamellar bodies were present in SP-C (-/-) type II cells, and tubular myelin was present in the alveolar lumen. Lung mechanics studies demonstrated abnormalities in lung hysteresivity (a term used to reflect the mechanical coupling between energy dissipative forces and tissue-elastic properties) at low, positive-end, expiratory pressures. The stability of captive bubbles with surfactant from the SP-C (-/-) mice was decreased significantly, indicating that SP-C plays a role in the stabilization of surfactant at low lung volumes, a condition that may accompany respiratory distress syndrome in infants and adults.     

Soluble beta-galactoside specific lectin is developmentally regulated in lungs of neonatal black mice and beige mice.

The beige mouse, a mutant of the C57 black mouse, is best known as a model of the Chediak-Higashi syndrome. Recently, it was found that alveolar maturation in neonatal beige mice is impaired, resulting in abnormally large alveoli. In guinea pigs, hamsters, and rats there is an elevated activity of a soluble, beta-galactoside-binding lectin in lungs at the age when alveolar maturation is in progress. Our present studies were done to find out if the temporal relationship between elevated lectin activity and alveolar maturation also occurs in mice and, further, if the impaired alveolar maturation in beige mice might be linked to the lectin. We found that the temporal relationship between lectin activity and alveolar maturation is also present in black and beige mice, with a peak in specific lectin activity occurring at about 8 days after birth. We also found that the major lectin purified from black or beige mice has essentially the same subunit molecular weight, isoelectric point, and amino acid composition. In conclusion, we found nothing abnormal about the lectin or its developmental regulation that can explain the impaired alveolar maturation in neonatal beige mice. The results do not rule out the possibility of an important role for the lectin in normal lung development or the possibility that some aspect of function or localization of the lectin or its ligands, not related to total lung lectin hemagglutinating activity, may be altered in the beige mouse.     

Female pseudohermaphroditism caused by a novel homozygous missense mutation of the GR gene

Familial glucocorticoid resistance is characterized by increased cortisol secretion without clinical evidence of hypercortisolism, but with manifestations of androgen and mineralocorticoid excess. This condition is mainly caused by mutations of the GR gene that cause inadequate transduction of the glucocorticoid signal in glucocorticoid target tissues. The clinical features of glucocorticoid resistance in females include hirsutism, acne, male pattern baldness, oligomenorrhea, and oligoanovulation. We describe here a new phenotype, female pseudohermaphroditism and severe hypokalemia, caused by a homozygous inactivating mutation of the GR gene. The proband was born with ambiguous genitalia from consanguineous parents and was mistreated as a 21-hydroxylase deficiency case since the age of 5 yr. She had very high levels of plasma ACTH (759 pg/ml or 167 pmol/liter) and high levels of cortisol (28-54 microg/dl or 772-1490 nmol/liter), androstenedione (5-14 ng/ml or 17-48 nmol/liter), T (174-235 ng/dl or 7-8 nmol/liter), and 17-hydroxyprogesterone (8-12 ng/ml or 24-36 nmol/liter). Her cortisol and 17-hydroxyprogesterone levels were not compatible with the diagnosis of classic congenital adrenal hyperplasia; furthermore, cortisol was not properly suppressed after dexamethasone administration (28 microg/d or 772 nmol/liter). Her laboratory evaluation indicated a diagnosis of glucocorticoid resistance. To investigate this puzzling clinical and biochemical picture, we analyzed both GR and CYP21 genes. Indeed, a homozygous T to C substitution at nucleotide 1844 in exon 5 of the GR gene was identified in the patient that caused a valine to alanine substitution at amino acid 571 in the ligand domain of the receptor. Her parents and an older sister were heterozygous for this mutation. A whole Epstein-Barr virus-transformed cell dexamethasone-binding assay revealed that this Ala(571) mutant had a 6-fold reduction in binding affinity compared with the wild-type receptor. In a functional assay using mouse mammary tumor virus promoter-driven luciferase reporter gene, the mutant receptor displayed 10- to 50-fold less trans-activation activity than the wild-type receptor. In addition, a large heterozygous CYP21 conversion was identified in the patient and her father. In conclusion, we described the first case of female pseudohermaphroditism caused by a novel homozygous GR gene mutation. This phenotype indicates that pre- and postnatal virilization can occur in females with the glucocorticoid resistance syndrome.     

Common polymorphisms in the glucocorticoid receptor gene are associated with adrenocortical responses to psychosocial stress

Chronic dysregulation of hypothalamus-pituitary-adrenal axis activity is related to several stress-related disorders. Evidence suggests that polymorphisms in the glucocorticoid receptor (GR) gene may have an impact on this neuroendocrine system. In the present investigation, 112 healthy males were studied to estimate the impact of three GR gene polymorphisms (BclI RFLP, N363S, ER22/23EK) on cortisol and ACTH responses to psychosocial stress (Trier Social Stress Test) and pharmacological stimulation (1 microg ACTH(1-24), 0.5 mg dexamethasone). Because only four ER22/23EK heterozygotes were identified, these subjects were not statistically analyzed. Compared with subjects with the wild-type GR genotype (n = 36), 363S allele carriers (n = 10) showed significantly increased salivary cortisol responses to stress, whereas the BclI genotype GG (n = 18) was associated with a diminished cortisol response. BclI heterozygotes and homozygotes (GG) exhibited a trend toward lower ACTH responses, compared with wild-type subjects and 363S carriers. The cortisol response to ACTH(1-24) administration was not significantly different between genotypes. After dexamethasone ingestion, 363S carriers showed a trend toward an enhanced cortisol suppression. This is the first report documenting an impact of GR gene polymorphisms on cortisol (and perhaps ACTH) responses to psychosocial stress. These variants may contribute to the individual vulnerability for hypothalamus-pituitary-adrenal-related disorders.