Fibroblast growth factor stimulates angiotensin converting enzyme expression in vascular smooth muscle cells. Possible mediator of the response to vascular injury.

Angiotensin converting enzyme (ACE) activity contributes to the vascular response to injury because ACE inhibition limits neointima formation in rat carotid arteries after balloon injury. To investigate the mechanisms by which ACE may contribute to vascular smooth muscle cell (VSMC) proliferation, we studied expression of ACE in vivo after injury and in vitro after growth factor stimulation. ACE activity 14 d after injury was increased 3.6-fold in the injured vessel. ACE expression, measured by immunohistochemistry, became apparent at 7 d in the neointima and at 14 d was primarily in the most luminal neointimal cells. To characterize hormones that induce ACE in vivo, cultured VSMC were exposed to steroids and growth factors. Among steroids, only glucocorticoids stimulated ACE expression with an 8.0 +/- 2.1-fold increase in activity and a 6.5-fold increase in mRNA (30 nM dexamethasone for 72 h). Among growth factors tested, only fibroblast growth factor (FGF) stimulated ACE expression (4.2 +/- 0.7-fold increase in activity and 1.6-fold increase in mRNA in response to 10 ng/ml FGF for 24 h). Dexamethasone and FGF were synergistic at the indicated concentrations inducing 50.6 +/- 12.4-fold and 32.5-fold increases in activity and mRNA expression, respectively. In addition, when porcine iliac arteries were transfected with recombinant FGF-1 (in the absence of injury), ACE expression increased in neointimal VSMC, to the same extent as injured, nontransfected arteries. The data suggest a temporal sequence for the response to injury in which FGF induces ACE, ACE generates angiotensin II, and angiotensin II stimulates VSMC growth in concert with FGF.

Glucocorticoids induce angiotensin-converting enzyme expression in vascular smooth muscle.

Angiotensin-converting enzyme (ACE) activity plays a central role in vessel growth and remodeling as shown by the fact that ACE inhibitors reduce neointimal proliferation after rat carotid injury. To investigate the mechanisms that regulate smooth muscle cell ACE expression, we studied the effects of steroids on ACE activity and mRNA in cultured rat aortic smooth muscle cells. ACE activity was present at low levels independent of growth state. In response to the glucocorticoid dexamethasone (100 nmol/L for 72 hours), ACE activity (hydrolysis of [3H]benzoyl-Phe-Ala-Pro) increased 10.1 +/- 3.1-fold. The increase in activity occurred within 12 hours and peaked after 72 hours of treatment. The increase in ACE activity was specific for glucocorticoids and paralleled their potency (dexamethasone > hydrocortisone = prednisolone). Dexamethasone increased the steady-state level of ACE mRNA in a concentration-dependent manner (21.4 +/- 0.4-fold at 100 nmol/L for 72 hours). Dexamethasone stimulation of ACE expression appeared to be due to both increased transcription and stabilization of ACE enzyme mRNA. This was suggested by the finding that dexamethasone stimulated nuclear run-on expression of ACE mRNA by only threefold, in contrast to the 21-fold increase in steady-state mRNA. These findings establish that ACE is a dynamically regulated enzyme in rat aortic smooth muscle cells. In addition, the present findings suggest an important role for stress steroids in the vascular response to injury in vivo.

Acute lymphoblastic leukemia with eosinophilia.

Acute lymphoblastic leukemia with eosinophilia is a rare but distinctive clinical entity. The eosinophilia in these patients can present before, concomitantly, or after the diagnosis of leukemia. Patients with this syndrome often suffer from the cardiovascular complications of severe eosinophilia, suffering excess morbidity and mortality as a result of their eosinophilia. Treatment of the eosinophilia in this syndrome consists of administration of induction chemotherapy, followed by prednisone and hydroxyurea if required for persistent eosinophilia. Eosinophilia often resolves with remission of leukemia, only to return at the time of relapse in a high percentage of cases. Patients with this syndrome characteristically have cytogenetic abnormalities involving the long arms of chromosomes 5 and 14. These cytogenetic abnormalities are not commonly seen in acute lymphoblastic leukemia and suggest that this syndrome may have a distinct pathophysiology and etiology. The affected region on chromosome 5 contains genes that control hematopoiesis, including eosinophilopoiesis. Further investigations into these cytogenetic abnormalities may provide insight into the etiology of the leukemia and eosinophilia characteristic of this syndrome.

Inhibition of host immunity by fluid and mononuclear cells from healing wounds.

Severe trauma impairs host immunity, which in turn renders the host susceptible to infection often terminating in death. This impairment occurs 7 to 14 days after injury, a time when wound healing is at its maximum. We examined the interactions of wound healing to host immunity by studying the in vitro and in vivo immune effects of wound components (i.e., wound fluid [WF] and wound mononuclear cells [WMNC]). Lewis male rats (RT-1(1] weighing 300 to 350 gm underwent 7 cm dorsal skin incisions and subcutaneous placement of polyvinyl alcohol sponges. At 7 and 10 days after wounding, sponges were removed and WF was separated from the cellular elements. The cell suspension was purified to contain 80% to 90% WMNC. Ten percent WF from 7- and 10-day-old wounds inhibits normal thymic lymphocyte blastogenesis to concanavalin A and phytohemagglutinin. Addition of 5 X 10(4) WMNC leads to similar inhibition. WF and WMNC from 10-day-old wounds also inhibit in vitro allogeneic responses tested in one way MLR of Lewis splenocytes with inactivated ACI (RT-1a) spleen cells by 75% to 96% and 85% to 98%, respectively. The inhibitory action of WF is heat resistant (56 degrees C for 30 minutes) and noncytotoxic. In vivo allogeneic responses, tested by grafting ACI skin onto Lewis recipients, were inhibited by intraperitoneal administration of 10-day-old WF (p less than 0.01). We conclude that WF contains factor(s) that inhibit in vitro and in vivo immune responses. WMNC exhibits the same action, suggesting that they may be the source of the WF inhibitory factor(s). These findings may explain host immunosuppression after severe trauma.

Adrenal insufficiency--an unusual cause of shock in postoperative patients.

OBJECTIVE: To remind physicians that adrenal insufficiency can cause postoperative shock and that the manifestations are difficult to distinguish from those of sepsis. METHODS: We present detailed case reports of three patients who had hyperdynamic shock in the surgical intensive-care unit and describe their response to the cosyntropin stimulation test. RESULTS: All three patients were diagnosed as having adrenal insufficiency with use of the cosyntropin stimulation test. Two of the three patients rapidly recovered; however, because of delay in the diagnosis of adrenal insufficiency, the third patient succumbed to multisystem organ failure. CONCLUSION: The cases presented highlight the need to exclude adrenal insufficiency as a possible cause of hyperdynamic circulatory shock, particularly when no clear-cut diagnosis exists. Early recognition of adrenal insufficiency is important and can result in reversal of shock and prevention of death. Adrenal insufficiency can be diagnosed through screening random cortisol levels and by use of the cosyntropin stimulation test. Patients in addisonian crisis often respond to the first dose of glucocorticoid with dramatic improvement in blood pressure and systemic vascular resistance. Administration of glucocorticoid can thus lead to improved organ perfusion and recovery of organ function. Delays in diagnosis and treatment of acute hypoadrenalism can have a fatal outcome.

Diagnosis of main-stem pulmonary thromboemboli by transesophageal echocardiography.

The aim of this report is to describe the usefulness of transesophageal echocardiography in the diagnosis of pulmonary emboli. A biplane transesophageal probe was used to examine the pulmonary artery in multiple views in three patients with suspected pulmonary emboli. The diagnosis of pulmonary emboli was made by transesophageal echocardiography in each of three patients when an echodense, circular or linear mass was seen in more than one view of the main or right pulmonary artery. In conclusion, our findings, coupled with previous case reports, suggest that transesophageal echocardiography should be considered in all critically ill patients with suspected pulmonary emboli.

Fluid shear stress stimulates platelet-derived growth factor expression in endothelial cells.

Fluid flow and the associated shear stress play a critical role in vascular growth and remodeling. Recent data suggest that increased endothelial cell expression of platelet-derived growth factor (PDGF) A- and B-chain by flow may participate in these events. In the present study, we examined the mechanism for flow-induced PDGF expression, focusing on protein kinase C (PKC). Bovine aortic endothelial cells were exposed to flow (shear stress = 30 dyn/cm2) in a parallel-plate flow chamber. Increases in PDGF B-chain, but not PDGF A-chain, were observed within 3 h, maximal within 6 h (13-fold increase), and sustained for 24 h. PKC appeared to be involved because phorbol 12-myristate 13-acetate induced PDGF B-chain mRNA. Activation of PKC alone, however, was insufficient to induce PDGF mRNA because the selective PKC activator, 1-oleoyl-2-acetyl-sn-glycerol, did not induce PDGF expression. A PKC-independent pathway was suggested by the fact that inhibition of PKC (downregulation with phorbol 12,13-dibutyrate or exposure to staurosporine) failed to block PMA or flow-induced PDGF B-chain expression. These results demonstrate flow-induced PDGF B-chain expression in endothelial cells that appears to be mediated, in part, by a PKC-independent pathway.

Lymphocyte participation in wound healing. Morphologic assessment using monoclonal antibodies.

To investigate lymphocyte participation in wound healing, the migration of T lymphocyte subsets into healing wounds and subcutaneously implanted polyvinyl alcohol sponges was studied. Frozen sections of 5-, 7-, and 10-day-old incisional wounds and sponges from Lewis rats were stained with mouse anti-rat monoclonal antibodies. Cellular staining to OX1 (all leucocyte), W3/25 (helper/effector T lymphocytes), and OX8 (suppressor/cytotoxic T lymphocytes) was quantitated in two arbitrarily defined areas based on maximal cellular infiltration: the superficial wound, down to and including the papillary dermis, and the deep wound, the reticular dermis. Five-day wounds were significantly more cellular than 10-day wounds in the deep portion (p less than 0.05) and somewhat more cellular in the superficial section (p less than 0.10). Approximately 2:1 W3/25 to OX8 ratios were noted for wound strips on all days. At 5 and 10 days there are twice as many W3/25 and OX8 labeled cells in the deep wound as in the superficial portion. At 7 days there is a peak in surface W3/25 and OX8 lymphocytes, whereas the deep population remains constant. Seven- and 10-day sponge granulomas demonstrate ratios similar to the wound strips (5-day sponge lymphocytic infiltration was insufficient to count). The data demonstrate that lymphocyte subpopulation participation in wound healing is a dynamic and distinctive process.

Bovine angiotensin converting enzyme cDNA cloning and regulation. Increased expression during endothelial cell growth arrest.

Angiotensin converting enzyme (ACE) is a zinc-containing dipeptidase that converts angiotensin I to angiotensin II, a powerful vasoconstrictor and smooth muscle growth factor. ACE activity has been shown to be dynamically regulated by hormones, ACE inhibitors, and endothelial cell growth state. To study how ACE expression is regulated, we isolated and sequenced the bovine ACE gene using both ACE-specific cDNA and genomic clones. Bovine ACE cDNA encodes a single polypeptide of 1,306 residues with a molecular mass of 150 kd. Bovine ACE is approximately 80% homologous to that of other species. It contains two homologous domains of equal size. Alignment of ACE sequences from bovine, human, mouse, and rabbit reveals that during evolution both domains have been highly conserved. We used the bovine ACE cDNA to study regulation of ACE gene expression during density-dependent growth arrest. As endothelial cells became growth-arrested (6 days after confluence), there was a 12-fold increase in ACE activity and a 90% decrease in DNA synthesis. Immunocytochemically detectable ACE markedly increased in growth-arrested cells. The increase in ACE was due to increased ACE gene expression, as assayed by RNase protection, which showed a 20-fold increase in ACE-specific mRNA. The present study shows that bovine ACE is highly regulated by endothelial cell growth state at the level of protein and mRNA expression. Such dynamic regulation may have important consequences for angiotensin II production during endothelial cell proliferation after arterial injury.

Intravenous hyperalimentation with high arginine levels improves wound healing and immune function.

The purpose of this study was to evaluate the effect of increased arginine levels in intravenous hyperalimentation (IVH) therapy on wound healing and thymic immune function. Groups of SD rats, 275-325 g, underwent placement of internal jugular catheter, 7-cm dorsal skin wounding, insertion of polyvinyl alcohol sponges subcutaneously, and closure of wounds with stainless-steel sutures. Twenty-four hours later, rats were started on IVH at a rate of 0.8-1 ml/100 g body wt/hr. All IVH solutions contained 20% dextrose, adequate amounts of minerals and vitamins, and two different amino acid mixtures: (A) Fre III (4.05 g ARG/liter) (n = 13); (B) experimental (7.50 g ARG/liter) (n = 11). Solutions were isonitrogenous, and contained similar amounts of essential amino acids. After 7 days of IVH, weight gain did not differ between the two groups; however, cumulative N balance was superior in group A. Wound healing was improved in group B as assessed by fresh wound strip breaking strength, fixed breaking strength, and the amount of reparative collagen deposition as assessed by the hydroxyproline content of the implanted sponges. Group B animals also had improved thymic function as assessed by thymic weight, the total number of thymic lymphocytes/gland and mitogenic reactivity of thymic lymphocytes to PHA and Con A. The experiments indicate that high arginine levels in IVH solutions improve wound healing and thymic immune function following injury.