OVA-induced airway hyperresponsiveness alters murine heart rate variability and body temperature

Altered autonomic (ANS) tone in chronic respiratory disease is implicated as a factor in cardiovascular co-morbidities, yet no studies address its impact on cardiovascular function in the presence of murine allergic airway (AW) hyperresponsiveness (AHR). Since antigen (Ag)-induced AHR is used to model allergic asthma (in which ANS alterations have been reported), we performed a pilot study to assess measurement feasibility of, as well as the impact of allergic sensitization to ovalbumin (OVA) on, heart rate variability (HRV) in a murine model. Heart rate (HR), body temperature (T_B), and time- and frequency-domain HRV analyses, a reflection of ANS control, were obtained in chronically instrumented mice (telemetry) before, during and for 22 h after OVA or saline aerosolization in sensitized (OVA) or Alum adjuvant control exposed animals. OVA mice diverged significantly from Alum mice with respect to change in HR during aerosol challenge (P < 0.001, Two-Way ANOVA; HR max change Ctrl = +80 ± 10 bpm vs. OVA = +1 ± 23 bpm, mean ± SEM), and displayed elevated HR during the subsequent dark cycle (P = 0.006). Sensitization decreased the T_B during aerosol challenge (P < 0.001). Sensitized mice had decreased HRV prior to challenge (SDNN: P = 0.038; Low frequency (LF) power: P = 0.021; Low/high Frequency (HF) power: P = 0.042), and increased HRV during Ag challenge (RMSSD: P = 0.047; pNN6: P = 0.039). Sensitized mice displayed decreased HRV subsequent to OVA challenge, primarily in the dark cycle (RMSSD: P = 0.018; pNN6: P ≤ 0.001; LF: P ≤ 0.001; HF: P = 0.040; LF/HF: P ≤ 0.001). We conclude that implanted telemetry technology is an effective method to assess the ANS impact of allergic sensitization. Preliminary results show mild sensitization is associated with reduced HRV and a suppression of the acute T_B-response to OVA challenge. This approach to assess altered ANS control in the acute OVA model may also be beneficial in chronic AHR models.

Vascular defects in gain-of-function fps/fes transgenic mice correlate with PDGF- and VEGF-induced activation of mutant Fps/Fes kinase in endothelial cells

BACKGROUND

Fps/Fes is a cytoplasmic tyrosine kinase that is abundantly expressed in the myeloid, endothelial, epithelial, neuronal and platelet lineages. Genetic manipulation in mice has uncovered potential roles for this kinase in hematopoiesis, innate immunity, inflammation and angiogenesis.

OBJECTIVE

We have utilized a genetic approach to explore the role of Fps/Fes in angiogenesis.

METHODS

A hypervascular line of mice generated by expression of a 'gain-of-function' human fps/fes transgene (fps(MF)) encoding a myristoylated variant of Fps (MFps) was used in these studies. The hypervascular phenotype of this line was extensively characterized by intravital microscopy and biochemical approaches.

RESULTS

fps(MF) mice exhibited 1.6-1.7-fold increases in vascularity which was attributable to increases in the number of secondary vessels. Vessels were larger, exhibited varicosities and disorganized patterning, and were found to have defects in histamine-induced permeability. Biochemical characterization of endothelial cell (EC) lines derived from fps(MF) mice revealed that MFps was hypersensitive to activation by vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF).

CONCLUSIONS

MFps mediates enhanced sensitization to VEGF and PDGF signaling in ECs. We propose that this hypersensitization contributes to excessive angiogenic signaling and that this underlies the observed hypervascular phenotype of fps(MF) mice. These phenotypes recapitulate important aspects of the vascular defects observed in both VEGF and angiopoietin-1 transgenic mice. The fps/fes proto-oncogene product therefore represents a novel player in the regulation of angiogenesis, and the fps(MF) line of mice constitutes a unique new murine model for the study of this process.

Calcium-independent contraction and sensitization of airway smooth muscle by p21-activated protein kinase

In Triton-skinned phasic ileal smooth muscle, constitutively active recombinant p21-activated kinase (PAK3) has been shown to induce Ca(2+)-independent contraction, which is accompanied by phosphorylation of caldesmon and desmin (Van Eyk JE, Arrell DK, Foster DB, Strauss JD, Heinonen TY, Furmaniak-Kazmierczak E, Cote GP, and Mak AS. J Biol Chem 273: 23433-23439, 1998). In the present study, we investigated whether PAK has a broad impact on smooth muscle in general by testing the hypothesis that PAK induces Ca(2+)-independent contractions and/or Ca(2+) sensitization in tonic airway smooth muscle and that the process is mediated via phosphorylation of caldesmon. In the absence of Ca(2+) (pCa > 9), constitutively active glutathione-S-transferase-murine PAK3 (GST-mPAK3) caused force generation of Triton-skinned canine tracheal smooth muscle (TSM) fibers to approximately 40% of the maximal force generated by Ca(2+) at pCa 4.4. In addition, GST-mPAK3 enhanced Ca(2+) sensitivity of contraction by increasing force generation by 80% at intermediate Ca(2+) concentrations (pCa 6.2), whereas it had no effect at pCa 4.4. Catalytically inactive GST-mPAK3(K297R) had no effect on force production. Using antibody against one of the PAK-phosphorylated sites (Ser(657)) on caldesmon, we showed that a basal level of phosphorylation of caldesmon occurs at this site in skinned TSM and that PAK-induced contraction was accompanied by a significant increase in the level of phosphorylation. Western blot analyses show that PAK1 is the predominant PAK isoform expressed in murine, rat, canine, and porcine TSM. We conclude that PAK causes Ca(2+)-independent contractions and produces Ca(2+) sensitization of skinned phasic and tonic smooth muscle, which involves an incremental increase in caldesmon phosphorylation.

Development of vitellogenin-ELISA, an in vivo bioassay, and identification of two vitellogenesis-inhibiting hormones of the tiger shrimp Penaeus monodon

A sandwich enzyme-linked immunosorbent assay (ELISA) for the quantification of vitellogenin in the hemolymph of Penaeus monodon is reported. Lipovitellin from the mature ovary was purified using hydroxylapatite column chromatography and used as the standard protein, which was serially diluted from 3336 to 6.51 microg and gave a linear plot. Sensitivity results showed ELISA was insensitive to samples that did not contain vitellogenin or lipovitellin. Specificity results showed the degree of the discrimination of the assay between positive samples (having vitellogenin or lipovitellin) and negative samples (devoid of vitellogenin or lipovitellin). Reproducibility studies showed that the intraassay coefficient of variation was 5.1% (n = 11) and the interassay coefficient of variation was 5.15% (n = 13). Separation of X-organ sinus gland peptides using a reversed phase column gave a total of 37 fractions. Two fractions were found to reduce the hemolymph vitellogenin concentration in a time-dependent manner and could be identified as vitellogenesis-inhibiting hormones I and II.

Role of vagal C-fiber afferents in the bronchomotor response to lactic acid in the newborn dog

We addressed the hypothesis that vagal C-fiber afferents and cyclooxygenase products are the mechanisms responsible for lactic acid (LA)-induced bronchoconstriction in the newborn dog. Perineural capsaicin and indomethacin were used to block conduction of vagal C fibers and production of cyclooxygenase products, respectively. Perineural capsaicin eliminated (85%) the increase in lung resistance (Rl; 45 ± 5.6%) due to capsaicin (25 μg/kg), whereas the increase in Rl (54 ± 6.9%) due to LA (0.4 mmol/kg) was only inhibited by 37 ± 4.7% ( P < 0.05). Atropine reduced LA-induced bronchoconstriction (42 ± 2.1%) by an amount similar to that obtained with perineural capsaicin. However, inhibition was significantly increased when atropine was combined with indomethacin (61 ± 2.7%; P < 0.05), implicating cyclooxygenase products in the LA-induced bronchoconstrictor response. We conclude that the mechanisms responsible for LA-induced bronchoconstriction in the newborn are 1) activation of vagal C-fibers, which, through projections to medullary respiratory centers, leads to activation of vagal cholinergic efferents; 2) production of cyclooxygenase products, which cause bronchoconstriction independent of medullary involvement; and 3) an unknown bronchoconstrictor mechanism, putatively tachykinin mediated. On the basis of our data, pharmaceutical targeting of pulmonary afferents would prevent multiple downstream mechanisms that lead to airway narrowing due to inflammatory lung disease.

Mechanisms of capsaicin- and lactic acid-induced bronchoconstriction in the newborn dog

1. Capsaicin activation of the pulmonary C fibre vanilloid receptor (VR1) evokes the pulmonary chemoreflex and reflex bronchoconstriction. Among potential endogenous ligands of C fibre afferents, lactic acid has been suggested as a promising candidate. We tested the hypotheses that (a) lactic acid behaves as a stimulant of C fibre receptors in the newborn dog to cause reflex bronchoconstriction, and (b) lactic acid causes reflex bronchoconstriction via the same pulmonary C fibre receptor mechanism as capsaicin using the competitive capsaicin/VR1 receptor antagonist capsazepine. 2. Right heart injection of lactic acid caused a significant increase (47 +/- 8.0 %) in lung resistance (RL) that was atropine sensitive (reduced by 75 %; P < 0.05), consistent with reflex activation of muscarinic efferents by stimulation of C fibre afferents. 3. Infusion of the competitive capsaicin antagonist capsazepine caused an 80 % reduction (P < 0.01) in the control bronchoconstrictor response (41 +/- 8.5 % increase in RL) to right heart injections of capsaicin. The effects of capsazepine are consistent with reversible blockade of the VR1 receptor to abolish C fibre-mediated reflex bronchoconstriction. 4. Lactic acid-evoked increases in RL were unaffected by VR1 blockade with capsazepine, consistent with a separate lactic acid-induced reflex mechanism. 5. We conclude that (a) putative stimulation of C fibres with lactic acid causes reflex bronchoconstriction in the newborn dog, (b) capsazepine reversibly antagonizes reflex bronchoconstriction elicited by right heart injection of capsaicin, presumably by attenuating capsaicin-induced activation of the C fibre 'capsaicin' receptor (VR1), and (c) capsazepine resistance of lactic acid-induced bronchoconstriction indicates that lactic acid evokes reflex bronchoconstriction by a separate mechanism, possibly via the acid-sensing ionic channel.

Quantitative densitometry of proteins stained with coomassie blue using a Hewlett Packard scanjet scanner and Scanplot software

In the present study we evaluated the performance of a software/scanner system that employed the Hewlett Packard (HP) ScanJet Plus and Scanplot Software for densitometric quantification of protein loads stained with Coomassie Brilliant Blue following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Gels with bovine serum albumin (BSA) standards, ranging from 0.125 to 10 micrograms, were scanned using reflectance densitometry with 127 microns step size in both the x and y directions and a resolution of 200 dots per inch. Densitometric volume was calculated for each protein band from scanner output in the tagged image file format (TIFF) by a customized software package, Scanplot V. 4.05 (Cunningham Engineering). Protein loads between 0.125 and 10.0 micrograms vs. volume were fit by a second-order regression: Volume = -0.58 x protein load2 + 16.82 x protein load + 7.87 (r = 0.991, p < 0.01). The same gels were scanned and quantified using a transmittance laser densitometer; densitometric volumes measured by both systems were highly correlated (r2 = 0.981, p < 0.01). Additional gels of BSA, smooth muscle myosin heavy chain (myosin), and actin displayed linear relationships between protein loads up to 4.0 micrograms and densitometric volume reflecting unique dye binding properties. We conclude that accurate and reproducible quantitative densitometry of SDS-PAGE can be performed using the HP ScanJet Plus scanner and Scanplot software.

Pulsatile release of immunoreactive luteinizing hormone (irLH) in hypophysectomized male rats

The concentration of plasma luteinizing hormone (LH) was monitored every minute by radioimmunoassay in male rats that were either hypophysectomized, or castrated and hypophysectomized. Castrated rats showed a pulsatile fluctuation of plasma immunoreactive LH (irLH) concentration with an elevated basal level, confirming previous work. The hypophysectomized and castrated hypophysectomized rats also showed pulsatile changes in plasma irLH concentration. This unexpected result indicates that ectopic irLH is not only actively released after hypophysectomy, but is released in pulses. The pulse interval was approximately 20 minutes for all 3 groups. The slope of the rate of decline of plasma irLH in the castrated rats is parallel to a theoretical disappearance rate of 5 min, while these slopes in the hypophysectomized and castrated hypophysectomized rats correspond to a 1 to 2-min disappearance rate. The difference in these slopes implies that the two irLH molecules may not be identical.