Myosin IIB and F-actin control apical vacuolar morphology and histamine-induced trafficking of H-K-ATPase-containing tubulovesicles in gastric parietal cells.

Selective inhibitors of myosin or actin function and confocal microscopy were used to test the role of an actomyosin complex in controlling morphology, trafficking, and fusion of tubulovesicles (TV) containing H-K-ATPase with the apical secretory canaliculus (ASC) of primary-cultured rabbit gastric parietal cells. In resting cells, myosin IIB and IIC, ezrin, and F-actin were associated with ASC, whereas H-K-ATPase localized to intracellular TV. Histamine caused fusion of TV with ASC and subsequent expansion resulting from HCl and water secretion; F-actin and ezrin remained associated with ASC whereas myosin IIB and IIC appeared to dissociate from ASC and relocalize to the cytoplasm. ML-7 (inhibits myosin light chain kinase) caused ASC of resting cells to collapse and most myosin IIB, F-actin, and ezrin to dissociate from ASC. TV were unaffected by ML-7. Jasplakinolide (stabilizes F-actin) caused ASC to develop large blebs to which actin, myosin II, and ezrin, as well as tubulin, were prominently localized. When added prior to stimulation, ML-7 and jasplakinolide prevented normal histamine-stimulated transformations of ASC/TV and the cytoskeleton, but they did not affect cells that had been previously stimulated with histamine. These results indicate that dynamic pools of actomyosin are required for maintenance of ASC structure in resting cells and for trafficking of TV to ASC during histamine stimulation. However, the dynamic pools of actomyosin are not required once the histamine-stimulated transformation of TV/ASC and cytoskeleton has occurred. These results also show that vesicle trafficking in parietal cells shares mechanisms with similar processes in renal collecting duct cells, neuronal synapses, and skeletal muscle.

Estradiol to Androstenedione Ratios Moderate the Relationship between Neurological Injury Severity and Mortality Risk after Severe Traumatic Brain Injury.

Early declines in gonadotropin production, despite elevated serum estradiol, among some individuals with severe traumatic brain injury (TBI) suggests amplified systemic aromatization occurs post-injury. Our previous work identifies estradiol (E2) as a potent mortality marker. Androstenedione (A), a metabolic precursor to E2, estrone (E1), and testosterone (T), is a steroid hormone substrate for aromatization that has not been explored previously as a biomarker in TBI. Here, we evaluated serum A, E1, T, and E2 values for 82 subjects with severe TBI. Daily hormone values were calculated, and E2:A and E1:T ratios were generated and then averaged for days 0-3 post-injury. After data inspection, mean E2:A values were categorized as above (high aromatization) and below (low aromatization) the 50th percentile for 30-day mortality assessment using Kaplan-Meier survival analysis and a multivariable Cox proportional hazard model adjusting for age, and Glasgow Coma Scale (GCS) to predict 30-day mortality status. Daily serum T, E1, and E2 were graphed by E2:A category. Serum E1 and E2 significantly differed over time (p < 0.05); the high aromatization group had elevated levels and a significantly lower probability of survival within the first 30 days (p = 0.0274). Multivariable Cox regression showed a significant E2:A*GCS interaction (p = 0.0129), wherein GCS predicted mortality only among those in the low aromatization group. E2:A may be a useful mortality biomarker representing enhanced aromatization after TBI. E2:A ratios may represent non-neurological organ dysfunction after TBI and may be useful in defining injury subgroups in which GCS has variable capacity to serve as an accurate early prognostic marker.

Systemic Estrone Production and Injury-Induced Sex Hormone Steroidogenesis after Severe Traumatic Brain Injury: A Prognostic Indicator of Traumatic Brain Injury-Related Mortality.

Extensive pre-clinical studies suggest that sex steroids are neuroprotective in experimental traumatic brain injury (TBI). However, clinical trials involving sex hormone administration have not shown beneficial results, and our observational cohort studies show systemic estradiol (E2) production to be associated with adverse outcomes. Systemic E2 is produced via aromatization of testosterone (T) or reduction of estrone (E1). E1, also produced via aromatization of androstenedione (Andro) and is a marker of T-independent E2 production. We hypothesized that E1 would be (1) associated with TBI-related mortality, (2) the primary intermediate for E2 production, and (3) associated with adipose tissue-specific aromatase transcription. We assessed 100 subjects with severe TBI and 8 healthy controls. Serum levels were measured on days 0-3 post-TBI for key steroidogenic precursors (progesterone), aromatase pathway intermediates (E1, E2, T, Andro), and the adipose tissue-specific aromatase transcription factors cortisol, tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6). E1 was elevated after TBI versus controls. High E1 was associated with higher progesterone, cortisol, and IL-6 (p < 0.05). Multivariable logistic regression demonstrated that those in the highest E1 tertile had increased odds for mortality (adjusted OR = 5.656, 95% CI = 1.102-29.045, p = 0.038). Structural equation models show that early serum E2 production is largely T independent, occurring predominantly through E1 metabolism. Acute serum E1 functions as a mortality marker for TBI through aromatase-dependent E1 production and T-independent E2 production. Further work should evaluate risk factors for high E2 production and how systemic E2 and its key intermediate E1 contribute to the extracerebral consequences of severe TBI.