Use of ab initio calculations to predict the biological potency of carboxylesterase inhibitors

Carboxylesterases are important enzymes responsible for the hydrolysis and metabolism of numerous pharmaceuticals and xenobiotics. These enzymes are potently inhibited by trifluoromethyl ketone containing (TFK) inhibitors. We demonstrated that the ketone hydration state was affected by the surrounding chemical moieties and was related to inhibitor potency, with inhibitors that favored the gem-diol conformation exhibiting greater potency. Ab initio calculations were performed to determine the energy of hydration of the ketone, and the values were correlated with esterase inhibition data for a series of carboxylesterase inhibitors. This system was examined in three different mammalian models (human liver microsomes, murine liver microsomes, and commercial porcine liver esterase) and in an insect enzyme preparation (juvenile hormone esterase). In all cases, the extent of ketone hydration was strongly correlated with biological potency. Our results showed a very strong correlation with the extent of hydration, accounting for 94% of activity for human liver microsome esterase inhibition (p < 0.01). The atomic charge on the carbon atom of the carbonyl group in the TFK also strongly correlated with inhibitor potency, accounting for 94% of inhibition activity in human liver microsomes (p < 0.01). In addition, we provide crystallographic evidence of intramolecular hydrogen bonding in sulfur-containing inhibitors and relate these data to gem-diol formation. This study provides insight into the mechanism of carboxylesterase inhibition and raises the possibility that inhibitors that too strongly favor the gem-diol configuration have decreased potency due to low rate of ketone formation.     

Comparison of skin stripping, in vitro release, and skin blanching response methods to measure dose response and similarity of triamcinolone acetonide cream strengths from two manufactured sources

The collective studies compare in vitro drug release, in vivo skin stripping, and skin blanching response methods for dose responsiveness and bioequivalence assessment of triamcinolone acetonide cream products, as a function of application duration, drug concentration, and manufacturer source. Commercially available triamcinolone acetonide creams (0.025%, 0.1%, and 0.5%) from two manufacturers were evaluated in vitro for rate and extent of drug release across synthetic membranes and in vivo for rate, extent, and variability of drug uptake into human stratum corneum and skin blanching response in human forearm skin. Data demonstrate that increasing triamcinolone acetonide cream concentration applied increased the rate and extent of drug released in vitro as well as the extent of drug uptake and skin blanching response in human skin in vivo. No difference (p < 0.05) between the two sources of 0.1% or 0.5% creams was measured by the skin stripping or skin blanching response methods. Dermatopharmacokinetic analysis of triamcinonide acetonide in vivo is therefore dose responsive to drug concentration applied and application duration and agrees with in vivo skin blanching results. Data support the use of dermatopharmacokinetic methods for bioequivalence and bioavailability assessment of topical drug products.     

Post-traumatic stress disorder in children and adolescents: epidemiology, diagnosis and treatment options

Post-traumatic stress disorder (PTSD) is a common psychiatric condition in childhood and adolescence. Rates vary widely depending upon the type of trauma exposure. Interpersonal traumas, such as rape or physical abuse, are more likely to result in PTSD than exposure to natural or technological disaster. Clinical presentations are exceedingly complex and children with PTSD are at increased risk of having comorbid psychiatric diagnoses. Because of its complexity and frequent occurrence with other disorders, assessment of PTSD necessitates a broad-based evaluation utilizing multiple informations and structured instruments specific to the symptoms of PTSD in youth. Cognitive-behavioral therapy (CBT) is the treatment of first choice. Pharmacological agents for PTSD treatment have received little empirical investigation in childhood. Pharmacological treatment is used to target disabling symptoms of the disorder, which limit psychotherapy or life functioning, by helping children to tolerate working through distressful material in therapy and life. Pharmacological treatment should be based on a stepwise approach utilizing broad spectrum medications such as the selective serotonin reuptake inhibitors as first-line agents. Comorbid conditions should be identified and treated with appropriate medication or psychosocial interventions. Treatment algorithms are provided to guide rational medication strategies for children and adolescents with PTSD, subsyndromal PTSD, and in PTSD that is comorbid with other psychiatric conditions of childhood. Reduction in even one debilitating symptom of PTSD can improve a child's overall functioning across multiple domains.     

IQGAP2 functions as a GTP-dependent effector protein in thrombin-induced platelet cytoskeletal reorganization

Human blood platelets are anucleate cells whose response to extracellular stimuli results in actin cytoskeleton rearrangements, thereby providing the critical initial step in the regulation of hemostasis. The serine protease alpha-thrombin, known to activate platelets by cleavage of a family of protease-activated receptors (PARs), is the most potent physiologic activator of human platelets, though downstream effector proteins uniquely linked to platelet cytoskeletal actin polymerization remain largely uncharacterized. The gene encoding the putative rac1/cdc42 effector protein IQGAP2 was identified within the PAR gene cluster at 5q13, flanked telomeric by PAR1 and encompassing PAR3. Immunofluorescence microscopy demonstrated IQGAP2 expression in filopodial extensions of activated platelets and colocalized with F-actin in lamellipodia and filopodia of IQGAP2-transfected COS1 cells. Platelet activation by alpha-thrombin, but not saturating concentrations of fibrillar collagen or adenosine 5'-diphosphate, uniquely assemble an IQGAP2/arp2/3-actin cytoplasmic complex, an association regulated by guanosine triphosphate rac1 ([GTP]rac1) but not by [GTP]cdc42. Likewise, only thrombin-activated platelets resulted in rapid translocation of IQGAP2 to the platelet cytoskeleton. These observations identify a physiologic scaffolding function for IQGAP2 and establish the presence of a functional genomic unit in humans uniquely evolved to regulate thrombin-induced platelet cytoskeletal actin reorganization.     

High-dose immune suppression and autologous hematopoietic stem cell transplantation in refractory Crohn disease

Two patients with severe Crohn disease, defined by a Crohn Disease Activity Index (CDAI) higher than 250 despite anti-tumor necrosis factor alpha (TNF-alpha), were treated by intense immune suppression and autologous hematopoietic stem cell transplantation (HSCT). Stem cells were mobilized from the peripheral blood using cyclophosphamide (2.0 g/m2) and granulocyte colony-stimulating factor (G-CSF; 5 micro g/kg/d), enriched ex vivo by CD34+ selection, and reinfused after immune conditioning with cyclophosphamide (200 mg/kg) and equine anti-thymocyte globulin (ATG; 90 mg/kg). Patients have remained in remission (CDAI < 100) for 1 year since HSCT. We conclude that further HSCT studies for severe Crohn disease appear warranted.     

The role of P-selectin in the immune destruction of platelets

Antibody-mediated platelet destruction is a poorly understood process, although several lines of evidence suggest that Fcgamma receptor (FcgammaR)-expressing splenic macrophages may be involved. In this study, chemiluminescence (CL) was used to measure the in vitro metabolic response of human monocytes to platelets sensitized with a human immunoglobulin (Ig)G1 recombinant antihuman platelet antigen-1a (anti-HPA-1a) antibody (B2G1; P-hrIgG1). CL responses were inhibited, but not abrogated, in the presence of 10 micro g/ml human IgG or murine IgG2a, suggesting that FcgammaRI was principally involved. Experiments to determine the effect of Fab fragments to FcgammaRII found that CL responses to P-hrIgG1 were significantly enhanced, indicating that crosslinking of monocyte FcgammaRII by platelet-bound hIgG may modulate concomitant activation by FcgammaRI. Several observations suggested that the CL responses to P-IgG were dependent on the activation of resting platelets during their co-culture with monocytes and their subsequent P-selectin-mediated adhesion. First, the magnitude of the CL response was related to the level of P-selectin expression following platelet activation with alpha-thrombin. Second, CL responses were inhibited in the presence of antibodies that block the binding of P-selectin to P-selectin glycoprotein ligand-1 but not when platelets were pretreated and then washed. Third, the addition of anti-HPA-1a to monocytes from HPA-1a-negative donors preincubated with HPA-1a-positive platelets resulted in rapid CL responses. Finally, PGI2 inhibited the CL response to resting P-hrIgG1. Thus, evidence is presented that the interaction of human monocytes with P-hrIgG1 is mediated by FcgammaRI, modulated via FcgammaRII, and enhanced by the presence of P-selectin on the platelet membrane.     

Psychotic depression and mortality

OBJECTIVE: Major depressive disorder is associated with elevated mortality rates that increase with the severity of depression. The authors hypothesized that patients with psychotic depression would have higher mortality rates than patients with nonpsychotic depression. METHOD: Survival analytic techniques were used to compare the vital status of 61 patients with psychotic major depression with that of 59 patients with nonpsychotic major depression up to 15 years after hospital admission. Medical status was assessed with the Cumulative Illness Rating Scale. Dexamethasone suppression test (DST) data were available for 101 patients. RESULTS: The mortality rate for subjects with psychotic depression was significantly greater than that for those with nonpsychotic depression, with 41% versus 20%, respectively, dying within 15 years after hospital admission. A proportional hazards model with age and medical status entered as covariates confirmed a significantly higher mortality rate in patients with psychotic depression (hazards ratio=2.31). A positive DST result was associated with psychotic depression but was not related to vital status. CONCLUSIONS: Patients with psychotic depression have a two-fold greater risk of death than do patients with severe, nonpsychotic major depression.