Triptolide attenuates pulmonary arterial hypertension and neointimal formation in rats

This paper reports the effect of triptolide (a diterpenoid triepoxide) on the development of monocrotaline (MCT)-induced pulmonary hypertension in pneumonectomized rats. Male Sprague- Dawley rats were injected with MCT (60 mg/kg) on Day 7 after left pneumonectomy. Rats received therapy from Day 5 to 35 with triptolide (0.25 mg/kg intraperitoneally, every other day, n = 10), or vehicle (0.1 ml of ethanol/cremophor intraperitoneally, every other day, n = 10). By Day 35, triptolide-treated rats demonstrated lower mean pulmonary arterial pressure (mPAP) than vehicle-treated rats (mPAP 21 +/- 3 versus 42 +/- 5 mm Hg, p < 0.001). Triptolide-treated rats also had significantly less right ventricular hypertrophy (RVH) and pulmonary arterial neointimal formation. In a rescue experiment, rats initiated therapy on Day 21. At Day 35, vehicle-treated rats (n = 4) had higher mPAP (40 +/- 9 mm Hg), greater RVH, and more severe pulmonary arterial neointimal formation than rats that received triptolide (0.25 mg/kg every other day, n = 7, mPAP 30 +/- 4 mm Hg) and rats that received triptolide (0.2 mg/kg daily, n = 7, mPAP 25 +/- 5 mm Hg, p < 0.01). In pneumonectomized rats that receive MCT, triptolide attenuates the development of pulmonary hypertension and RVH, and promotes regression of pulmonary arterial neointimal formation.

Characterization of Hoxa-10/Hoxa-11 transheterozygotes reveals functional redundancy and regulatory interactions

Hox genes show related sequences and overlapping expression domains that often reflect functional redundancy as well as a common evolutionary origin. To accurately define their functions, it has become necessary to compare phenotypes of mice with single and multiple Hox gene mutations. Here, we focus on two Abd-B-type genes, Hoxa-10 and Hoxa-11, which are coexpressed in developing vertebrae, limbs, and reproductive tracts. To assess possible functional redundancy between these two genes, Hoxa-10/Hoxa-11 transheterozygotes were produced by genetic intercrosses and analyzed. This compound mutation resulted in synergistic defects in transheterozygous limbs and reproductive tracts, but not in vertebrae. In the forelimb, distal radial/ulnar thickening and pisiform/triangular carpal fusion were observed in 35 and 21% of transheterozygotes, respectively, but were effectively absent in Hoxa-10 and Hoxa-11 +/- forelimbs. In the hindlimb, distal tibial/fibular thickening and loss of tibial/fibular fusion were observed in >80% of transheterozygotes but in no Hoxa-10 or Hoxa-11 +/- hindlimbs, and all transheterozygotes displayed reduced medial patellar sesamoids, compared to modest incidences in Hoxa-10 and Hoxa-11 +/- mutants. Furthermore, while the reproductive tracts of Hoxa-10 and Hoxa-11 single heterozygous mutants of both sexes were primarily unaffected, male transheterozygotes displayed cryptorchidism and abnormal tortuosity of the ductus deferens, and female transheterozygotes exhibited abnormal uterotubal junctions and narrowing of the uterus. In addition we observed that the targeted mutations of Hoxa-10 and Hoxa-11 each affected the expression of the other gene in the developing prevertebra and reproductive tracts. These results provide a measure of the functional redundancy of Hoxa-10 and Hoxa-11 and a deeper understanding of the phenotypes resulting in the single mutants and help elucidate the regulatory interactions between these two genes.

Abdominal B (AbdB) Hoxa genes: regulation in adult uterus by estrogen and progesterone and repression in müllerian duct by the synthetic estrogen diethylstilbestrol (DES)

Mice deficient for the Abdominal B (AbdB) Hox gene Hoxa-10 exhibit reduced fertility due to defects in implantation. During the peri-implantation period Hoxa-10 is sequentially expressed in the uterine epithelium and stroma. These observations, combined with the stringent regulation of uterine implantation by ovarian steroids, prompted us to test whether estrogen and progesterone directly regulate the expression of Hoxa-10 and other AbdB Hoxa genes. Here we show that Hoxa-10 expression in the adult uterus is strongly activated by progesterone. This activation is blocked by the progesterone receptor antagonist RU486 and is independent of new protein synthesis. In addition, Hoxa-10 expression is repressed by estrogen in a protein synthesis-independent manner. Analysis of adjacent AbdB Hoxa genes reveals that Hoxa-9 and a-11 are also activated in a colinear fashion by progesterone but differentially regulated by estrogen. These results suggest that the regulation of AbdB Hox gene expression in the adult uterus by ovarian steroids is a property related to position within the cluster, mediated by the direct action of estrogen and progesterone receptors upon these genes. We next examined whether the embryonic expression of Hoxa10 is regulable by hormonal factors. Previous work has demonstrated that perinatal administration of the synthetic estrogen diethylstilbestrol (DES) to mice and humans produces uterine, cervical, and oviductal malformations. Certain of these phenotypes resemble those in Hoxa-10 knockout mice, suggesting that Hoxa-10 gene expression might be repressed by DES during reproductive tract morphogenesis. Exposure of the developing female reproductive tract to DES, either in vivo or in organ culture, represses the expression of Hoxa-10 in the Müllerian duct. Thus, these data not only establish a direct link between ovarian steroids and AbdB Hoxa gene expression in the adult uterus, but also provide a potential mechanism for the teratogenic effects of DES on the developing reproductive tract.

Mechanisms of reduced fertility in Hoxa-10 mutant mice: uterine homeosis and loss of maternal Hoxa-10 expression

The establishment of a receptive uterine environment is critical for embryonic survival and implantation. One gene that is expressed in the uterus during the peri-implantation period in mice and is required for female fertility is the homeobox gene Hoxa-10. Here we characterize the peri-implantation defects in Hoxa-10 mutant females and investigate functions of Hoxa-10 in the uterine anlage during morphogenesis and in the adult uterus during pregnancy. Examination of pregnancy in Hoxa-10 mutant females has revealed failure of implantation as well as resorption of embryos in the early postimplantation period. Morphologic analysis of the mutant uterus has demonstrated homeotic transformation of the proximal 25% into oviduct. Histology and molecular markers confirm this anterior transformation. Furthermore, in situ hybridization shows that this region coincides with the anterior limit of embryonic Hoxa-10 expression in the urogenital ducts and a parallel transformation is observed in Hoxa-10 mutant males at the junction of the epididymis and ductus deferens. Female fertility could be compromised by either the homeotic transformation or the absence of Hoxa-10 function in the adult during pregnancy. To distinguish between these two potential mechanisms of infertility, wildtype blastocysts were transferred into mutant uteri distal to the transformed region on day 2.5 of pseudopregnancy. This procedure did not rescue the phenotype, suggesting that adult uterine expression of Hoxa-10 is required during pregnancy. Moreover, when implantation was experimentally delayed, homozygous uteri were able to support survival of blastocysts comparable to wild-type controls, indicating that the requirement for Hoxa-10 is intrinsic to implantation. While expression of LIF and HB-EGF appears unaffected in the mutant uteri, a decrease is observed in the intensity and number of blue dye reactions, an indicator of increased vascular permeability in response to implantation. In addition, mutant uteri exhibited decreased decidualization in response to artificial stimuli. These results show that Hoxa-10 is required during morphogenesis for proper patterning of the reproductive tract and in the adult uterus for peri-implantation events.

Pulmonary capillary pressure measurement from pulmonary artery occlusion pressure decay profile analysis in sheep

Pulmonary capillary pressure (Ppc), the major factor responsible for pulmonary edema, cannot be directly measured in intact subjects but may be estimated by analysis of the pressure decay profile after pulmonary artery catheter balloon inflation. We compared three different methods of pulmonary artery occlusion pressure (Ppao) decay profile analysis to estimates of Ppc derived from lymph flow measurements in halothane-anesthesized sheep. The relationship between Ppc and lymph flow was first determined by increasing Ppc by left atrial balloon inflation, and was then used to determine Ppc during pulmonary hypertension produced by infusion of a thromboxane analog. All three methods of Ppao decay profile analysis demonstrated a correlation with Ppc estimated from lymph flow. However, the method using a single exponential analysis significantly overestimated Ppc, and none of the methods reliably estimated changes in the longitudinal distribution of pulmonary vascular resistance during pulmonary hypertension. These results suggest that Ppao decay profile analysis as currently performed has limited application.

The expression pattern of the murine Hoxa-10 gene and the sequence recognition of its homeodomain reveal specific properties of Abdominal B-like genes

Homeobox genes of the Abdominal B (AbdB) family constitute a distinct subset of vertebrate Hox genes. Analysis of the murine Hoxa-10 gene, one member of this family, revealed several properties specific to this class. Two transcripts of Hoxa-10, a10-1 and a10-2, encode homeodomain proteins of 55 kDa (399 amino acids) and 16 kDa (96 amino acids), respectively. These proteins have identical homeodomains and C-terminal regions encoded by a common 3' exon but differ significantly in the sizes of their N-terminal regions because of the usage of alternative 5' exons. The 5' exon of the a10-2 form is also present in transcripts of Hoxa-9, the next 3' gene, indicating that splicing can occur between adjacent AbdB Hox genes within a cluster. Both Hoxa-10 transcripts demonstrated identical patterns of expression in the posterior body and proximal limb bud, differentiating them from AbdB morphogenetic and regulatory transcripts and suggesting a role with other AbdB Hox genes in the patterning of these structures. Finally, a binding site selection identified the sequence AA(A/T)TTTTATTAC as the Hoxa-10 homeodomain consensus binding site, with a TTAT core sequence. Preferential recognition of a TTAT core therefore differentiates the AbdB class from Antennapedia (Antp) class gene products which bind a TAAT core. Thus, in vertebrates, structural similarities, coordinate transcriptional regulation, sites of expression, and binding site preferences all serve to distinguish AbdB from Antp Hox genes.

Longitudinal distribution of pulmonary vascular resistance after endotoxin administration in sheep

BACKGROUND AND METHODS

Pulmonary hypertension may increase pulmonary capillary pressure and exacerbate pulmonary edema in acute respiratory failure. The effects of pulmonary hypertension on pulmonary capillary pressure depend on the longitudinal distribution of pulmonary vascular resistance. Since pulmonary hypertension occurs during acute respiratory failure, we hypothesized that acute respiratory failure may produce time-dependent changes in the longitudinal distribution of pulmonary vascular resistance. Therefore, we measured pulmonary capillary pressure and the longitudinal distribution of pulmonary vascular resistance in an animal model of acute respiratory failure. Escherichia coli endotoxin (2.5 to 5.0 micrograms/kg) was administered over a 1-hr period in eight anesthetized sheep. Pulmonary and systemic hemodynamics, including pulmonary artery occlusion pressure (PAOP), pulmonary capillary pressure, and the longitudinal distribution of pulmonary vascular resistance, were measured over the next 5 hrs. Pulmonary capillary pressure was estimated by analysis of the pressure decay following pulmonary artery balloon inflation.

RESULTS

Endotoxin administration resulted in sustained pulmonary hypertension for the subsequent 5 hrs of the study. Pulmonary capillary pressure was increased 7 mm Hg above baseline at 0.5 and 0.75 hrs during the infusion of endotoxin but returned to baseline values at 1.5 hrs. Despite sustained pulmonary hypertension, pulmonary capillary pressure remained at baseline values for the duration of the study. Similar to pulmonary capillary pressure, pulmonary venous (or postcapillary) resistance was increased approximately four-fold over baseline at 0.5 and 0.75 hrs after initiating endotoxin administration, but returned to baseline values by the end of endotoxin administration and remained at baseline values throughout the remainder of the study. In contrast, pulmonary arterial (or precapillary) resistance remained at values approximately three times baseline during the infusion and throughout the duration of the study.

CONCLUSIONS

In this experimental model of acute respiratory failure, the effects of endotoxin on the longitudinal distribution of pulmonary vascular resistance are time-dependent. If these data from animals can be extrapolated to humans, we speculate that the importance of pulmonary venoconstriction in exacerbating pulmonary edema may vary over time in patients with acute respiratory failure.

A thromboxane analog increases pulmonary capillary pressure but not permeability in the perfused rabbit lung

Thromboxane has been implicated as a mediator of pulmonary hypertension and pulmonary edema in acute respiratory failure. Pulmonary edema may result from increased pulmonary capillary hydrostatic pressure or from increased pulmonary vascular permeability. We therefore studied the effects of a stable thromboxane analog, U46619, on these two parameters in the perfused rabbit lung. Pulmonary capillary pressure was measured by the double vascular occlusion method, and pulmonary vascular permeability was estimated by measurement of the pulmonary fluid filtration coefficient (Kf). U46619 infusion produced pulmonary hypertension and lung weight gain; increased both the arterial (precapillary) and venous (postcapillary) components of pulmonary vascular resistance; and increased pulmonary capillary pressure from 4.7 +/- 0.5 to 9.0 +/- 0.7 mmHg (P less than 0.01). The isogravimetric pressure (equivalent to the capillary pressure corresponding to no lung weight gain) was 4.0 +/- 0.4 mmHg before U46619 and 4.6 +/- 0.4 mmHg during U46619. Therefore, U46619 significantly increased capillary pressure above isogravimetric pressure and resulted in the development of pulmonary edema. U46619 did not affect vascular permeability as measured by Kf. We conclude that pulmonary venoconstriction resulting in increased pulmonary capillary hydrostatic pressure is the major mechanism by which thromboxane produces pulmonary edema in isolated lungs.

Effect of hyperglycemia on neuronal changes in a rabbit model of focal cerebral ischemia

In clinical medicine, cerebral ischemia is frequently due to a focal, rather than global, insult. The effect of hyperglycemia in focal cerebral ischemia is not well defined. We studied the effect of hyperglycemia on neuropathologic changes in a rabbit model of focal cerebral ischemia. Rabbits were randomized to receive saline (n = 12) or glucose (n = 12) infusions. The left anterior cerebral and left internal carotid arteries were clipped after the infusion began. After 6 hours of occlusion, the area of severe ischemic neuronal damage in the left neocortex and striatum on two standard sections of brain was calculated and expressed as a percentage of the total area of the left cortex or striatum. The mean +/- SEM cortical area of severe ischemic neuronal damage was 22.1 +/- 2.8% in the glucose-treated rabbits and 34.0 +/- 4.6% in the saline-treated rabbits (p less than 0.05). The cortical area of severe ischemic neuronal damage was inversely correlated with plasma glucose concentration at the time of arterial clipping (p less than 0.05). We conclude that hyperglycemia is associated with decreased histologic neuronal injury in this model of focal cerebral ischemia and may be protective when cerebral ischemia occurs from a focal insult.