Differential Responses of the HPA Axis to Mild Blast Traumatic Brain Injury in Male and Female Mice

Traumatic brain injury (TBI) affects 10 million people worldwide, annually. TBI is linked to increased risk of psychiatric disorders. TBI, induced by explosive devices, has a unique phenotype. Over one-third of people exposed to blast-induced TBI (bTBI) have prolonged neuroendocrine deficits, shown by anterior pituitary dysfunction. Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis is linked to increased risk for psychiatric disorders. Not only is there limited information on how the HPA axis responds to mild bTBI (mbTBI), sex differences are understudied. We examined central and peripheral HPA axis reactivity, 7 to 10 days after mbTBI in male and female mice. Males exposed to mbTBI had increased restraint-induced serum corticosterone (CORT), but attenuated restraint-induced corticotropin-releasing factor (CRF)/c-Fos-immunoreactivity (ir) in the paraventricular nucleus of the hypothalamus (PVN). Females displayed an opposite response, with attenuated restraint-induced CORT and enhanced restraint-induced PVN CRF/c-Fos-ir. We examined potential mechanisms underlying this dysregulation and found that mbTBI did not affect pituitary (pro-opiomelanocortin and CRF receptor subtype 1) or adrenal (11β-hydroxylase, 11β-dehydrogenase 1, and melanocortin 2 receptor) gene expression. mbTBI did not alter mineralocorticoid or glucocorticoid gene expression in the PVN or relevant limbic structures. In females, but not males, mbTBI decreased c-Fos-ir in non-neuroendocrine (presumably preautonomic) CRF neurons in the PVN. Whereas we demonstrated a sex-dependent link to stress dysregulation of preautonomic neurons in females, we hypothesize that mbTBI may disrupt limbic pathways involved in HPA axis coordination in males. Overall, mbTBI altered the HPA axis in a sex-dependent manner, highlighting the importance of developing therapies to target individual strategies that males and females use to cope with mbTBI.

IFITM3 regulates fibrinogen endocytosis and platelet reactivity in nonviral sepsis

Platelets and megakaryocytes are critical players in immune responses. Recent reports suggest infection and inflammation alter the megakaryocyte and platelet transcriptome to induce altered platelet reactivity. We determined whether nonviral sepsis induces differential platelet gene expression and reactivity. Nonviral sepsis upregulated IFN-induced transmembrane protein 3 (IFITM3), an IFN-responsive gene that restricts viral replication. As IFITM3 has been linked to clathrin-mediated endocytosis, we determined whether IFITM3 promoted endocytosis of α-granule proteins. IFN stimulation enhanced fibrinogen endocytosis in megakaryocytes and platelets from Ifitm+/+ mice, but not Ifitm-/- mice. IFITM3 overexpression or deletion in megakaryocytes demonstrated IFITM3 was necessary and sufficient to regulate fibrinogen endocytosis. Mechanistically, IFITM3 interacted with clathrin and αIIb and altered their plasma membrane localization into lipid rafts. In vivo IFN administration increased fibrinogen endocytosis, platelet reactivity, and thrombosis in an IFITM-dependent manner. In contrast, Ifitm-/- mice were completely rescued from IFN-induced platelet hyperreactivity and thrombosis. During murine sepsis, platelets from Ifitm+/+ mice demonstrated increased fibrinogen content and platelet reactivity, which was dependent on IFN-α and IFITMs. Platelets from patients with nonviral sepsis had increases in platelet IFITM3 expression, fibrinogen content, and hyperreactivity. These data identify IFITM3 as a regulator of platelet endocytosis, hyperreactivity, and thrombosis during inflammatory stress.

Bioequivalence of two oral contraceptive drugs containing norethindrone and ethinyl estradiol

Two oral contraceptive drugs, Formulation A and Formulation B, both of similar hormonal content, were compared with each other to determine if they were bioequivalent. Both drugs contain 1 mg of norethindrone (NET) and 0.035 mg of ethinyl estradiol (EE). Application of an interval test for the ratio of the computed parameter means demonstrated equivalence for the two formulations with respect to the 0-24 hour area under the plasma level versus time curve (AUC24), the total area under the curve (AUCtot) and for the maximum plasma concentration (Cmax) for both ethinyl estradiol and norethindrone. The data support the hypothesis for bioequivalence of the two formulations with respect to total absorption.

Pharmacokinetics of norethindrone: effect of particle size

In 24 healthy women between the ages of 19 and 35 years who had not used oral contraceptive preparations for at least 60 days, it was found that the smaller the particle size of norethindrone (NET) administered, the higher was the plasma NET level obtained. Three different preparations having particle sizes of NET smaller than 250 microns, 44 microns or 10 microns were tested in a crossover pattern. The time required to reach maximum plasma concentration (Tmax) became shorter with decreasing particle size, 1.69 hr, 1.52 hr and 1.06 hr, respectively. As particle size was reduced, the maximum NET plasma concentration (Cmax) increased for the 3 different 1 mg NET preparations, i.e. 8.66 ng/ml, 10.53 ng/ml and 15.73 ng/ml. A trial with a 2 mg NET preparation made with NET utilizing the 44 microns same material displayed a Tmax similar to the 1 mg NET preparation having the same particle size while the Cmax reached a level of 17.56 ng/ml. The area under the plasma concentration versus time curve from 0-24 hrs and the extrapolated total area under the curve, increased with decreasing particle size. The use of a smaller particle size allows for more rapid dissolution or oral contraceptive tablets when measured in vitro; however, there is no evidence that such faster dissolution leads to a significant difference in efficacy. Oral contraceptive tablets have, since their inception, utilized both large and small NET particle size material in various preparations.

Bioequivalence of norethindrone and ethinyl estradiol for two different weight tablets with the same hormonal content

Two tablets of differing weights, 100 mg (A) and 50 mg (B), of an oral contraceptive drug (OC) were compared with each other and to a solution (C) of the same components. The composition of the OC consisted of 1 mg of norethindrone (NET) and 0.035 mg of ethinyl estradiol (EE2). Both tablets were shown to differ from the solution, which was more rapidly absorbed, but were not significantly different from each other. Formulation means for NET and EE2, for each of the two products, were similar. Application of an interval test for the ratio of computed parameters demonstrated equivalence of the two formulations with respect to 0-24 hr area under the curve (AUC24) and total area under the curve (AUC+o+) for both NET and EE2 and with respect to concentration maximum (Cmax) for EE2. The data support the hypothesis for bioequivalence of the two formulations with respect to total absorption.

Effect on fecal output of various dietary nitrogen sources in pig-tailed monkeys (Macaca nemestrina) fed fiber-free, semisynthetic diets

Fiber-free liquid diets containing isonitrogenous amounts of various dietary nitrogen sources were fed to five adult male pig-tailed monkeys (Macaca nemestrina) with a mean weight of approximately 10 kg. All liquid diets supplied 3.0 g N/DAY PER MONKEY AND MAINTAINED THE ANIMALS IN A POSTIVE NITROGEN BALANCE. Initial baseline fecal output data were obtained by feeding the animals a commercial solid monkey chow. The dietary nitrogen sources fed were a) egg white protein, b) an enzymatic hydrolysate of fish protein supplemented with L-amino acids to simulate the egg albumin pattern, c) a mixture of pure L-amino acids simulating the egg pattern, d) a casein hydrolysate supplemented with amino acids, and e) an amino acid mixture with Rose's pattern. Total fecal matter, dry fecal matter, percent of moisture, fecal nitrogen, lipids and ash were determined for a 10-day period for each experimental diet. A very significant difference (P smaller than 0.001) was noted between each liquid diet and the solid chow, but no significant differences were found between the various fiber-free liquid diets, pointing to the effect of fiber as a major factor affecting fecal output. Monkeys fed liquid diets excreted fecal matter with a mean of 12.9 g/day, of which 4.7 g/day was dry feces (fecal dry matter 28.5%). Fecal nitrogen was found to be 0.25 g, fecal lipids were 0.19 g, and fecal ash was 0.59 g/day per monkey, respectively.

Abstract 014: Interferon-induced Transmembrane 3 (IFITM3) on Megakaryocytes and Platelets Regulates Fibrinogen Endocytosis and Thrombosis During Inflammation

Introduction: IFITM3, an interferon (IFN) responsive gene, restricts pathogen replication through vesicular trafficking mechanisms. IFITM3 in megakaryocytes (MKs) and platelets has not been examined. We hypothesized that in MKs and platelets, IFITM3 regulates the endocytosis of pro-coagulant proteins, aggregation, and thrombosis.

Methods: the regulation of IFITM3 gene expression was determined in MKs and platelets under inflammatory stimuli. Fibrinogen (Fgn) endocytosis, a clathrin-mediated event requiring αIIbβ3, and transferrin endocytosis, a clathrin-mediated, αIIbβ3-independent event, were examined in stimulated MKs and platelets from wild type (WT) and Ifitm -/- mice (KO). Integrin αIIbβ3 activation, platelet aggregation, and thrombosis was determined in WT and Ifitm -/- mice upon IFNα-stimulation. Co-immunoprecipitation identified interaction partners for IFITM3. To establish human relevance, IFITM3 expression, Fgn content, and aggregation was measured in platelets from septic patients, where systemic IFNs are increased.

Results: IFNs significantly induced IFITM3 expression in MKs and platelets (p<0.001). Upregulation of IFITM3 by IFNs increased Fgn and transferrin endocytosis in MKs (2-fold vs. NT, p<0.05). Co-IP demonstrated a specific IFITM3 interaction between clathrin and αIIb. Upon IFN stimulation, IFITM3, clathrin, and αIIb shifted into lipid rafts. Increased Fgn endocytosis by IFNs enhanced platelet aggregation and accelerated death (~2-fold increased) due to platelet-dependent thrombosis (p<0.05 for all comparisons). In KO mice, enhanced Fgn endocytosis, platelet aggregation, and thrombosis to IFNs was completely prevented, demonstrating the necessity of IFITMs for these functional responses. Platelets from septic patients mirrored findings in mice with a ~20-fold increase in IFITM3 protein expression, with shifts into lipid rafts, compared to healthy controls (p<0.0001). Increased platelet IFITM3 expression was associated with greater platelet Fgn content and significant increases in platelet aggregation (20% increase, p<0.05).

Conclusions: Our data identify IFITM3 as a previously unknown regulator of MK and platelet endocytosis and thrombosis under inflammatory stimuli in humans and mice.