Pseudomonas aeruginosa elastase disrupts the cortisol-binding activity of corticosteroid-binding globulin.

The serine protease inhibitor (SERPIN) family member corticosteroid-binding globulin (CBG) is the main carrier of glucocorticoids in plasma. Human CBG mediates the targeted release of cortisol at sites of inflammation through cleavage of its reactive center loop (RCL) by neutrophil elastase. The RCLs of SERPIN family members are targeted by diverse endogenous and exogenous proteases, including several bacterial proteases. We tested different bacteria for their ability to secrete proteases that disrupt CBG cortisol-binding activity, and characterized the responsible protease and site of CBG cleavage. Serum CBG integrity was assessed by Western blotting and cortisol-binding capacity assay. Effects of time, pH, temperature, and protease inhibitors were tested. Proteolytically active proteins from bacterial media were purified by fast protein liquid chromatography, and the active protease and CBG cleavage sites were identified by mass spectrometry. Among the bacteria tested, medium from Pseudomonas aeruginosa actively disrupted the cortisol-binding activity of CBG. This proteolytic activity was inhibited by zinc chelators and occurred most efficiently at pH 7 and elevated physiological temperature (ie, 41°C). Mass spectrometric analysis of a semi-purified fraction of P. aeruginosa media identified the virulence factor LasB as the responsible protease, and this was confirmed by assaying media from LasB-deficient P. aeruginosa. This metalloprotease cleaves the CBG RCL at a major site, distinct from that targeted by neutrophil elastase. Our results suggest that humoral responses to P. aeruginosa infection are influenced by this pathogen's ability to secrete a protease that promotes the release of the anti-inflammatory steroid, cortisol, from its plasma transport protein.

Prenatal SSRI exposure alters neonatal corticosteroid binding globulin, infant cortisol levels, and emerging HPA function.

BACKGROUND: Serotonin influences the development of the hypothalamic-pituitary-adrenal (HPA) system; therefore prenatal exposure to selective serotonin reuptake inhibitor antidepressants (SSRIs) may alter HPA axis development and function. To address this, prenatal exposure to SSRIs and maternal mood were examined in relation to neonatal and infant levels of cortisol and its binding protein, corticosteroid-binding globulin (CBG). METHODS: Serum cortisol and CBG levels were assayed from SSRI-exposed and non-exposed mothers and their neonates at delivery. Maternal mood symptoms were documented at 36 weeks gestation. To determine the long-term implications of changes in CBG, levels of salivary cortisol were assessed in infants at 3 months of age. RESULTS: Prenatal SSRI exposure significantly increased serum CBG levels in neonates after vaginal delivery (p ≤ 0.038), even when controlling for maternal depression. Neonatal serum cortisol levels did not vary with SSRI exposure or antenatal maternal mood, but were significantly higher following vaginal delivery (p ≤ 0.003). Neonatal serum CBG levels were associated with infant salivary levels of evening cortisol (p ≤ 0.051). In SSRI-exposed infants, increased levels of neonatal CBG predicted a smaller diurnal change in infant salivary cortisol (p ≤ 0.028), regardless of maternal depression. CONCLUSIONS: Prenatal SSRI exposure affects the developing HPA system by altering serum CBG levels in neonates and infant salivary cortisol levels. Further research is warranted on the long-term functional implications of the effect of prenatal SSRI exposure on fetal hepatic CBG gene expression and the developing HPA system.