Heme oxygenase-1 deficiency accelerates formation of arterial thrombosis through oxidative damage to the endothelium, which is rescued by inhaled carbon monoxide.

Heme oxygenase (HO)-1 (encoded by Hmox1) catalyzes the oxidative degradation of heme to biliverdin and carbon monoxide. HO-1 is induced during inflammation and oxidative stress to protect tissues from oxidative damage. Because intravascular thrombosis forms at sites of tissue inflammation, we hypothesized that HO-1 protects against arterial thrombosis during oxidant stress. To investigate the direct function of HO-1 on thrombosis, we used photochemical-induced vascular injury in Hmox1-/- and Hmox1+/+ mice. Hmox1-/- mice developed accelerated, occlusive arterial thrombus compared with Hmox1+/+ mice, and we detected several mechanisms accounting for this antithrombotic effect. First, endothelial cells in Hmox1-/- arteries were more susceptible to apoptosis and denudation, leading to platelet-rich microthrombi in the subendothelium. Second, tissue factor, von Willebrand Factor, and reactive oxygen species were significantly elevated in Hmox1-/- mice, consistent with endothelial cell damage and loss. Third, following transplantation of Hmox1-/- donor bone marrow into Hmox1+/+ recipients and subsequent vascular injury, we observed rapid arterial thrombosis compared with Hmox1+/+ mice receiving Hmox1+/+ bone marrow. Fourth, inhaled carbon monoxide and biliverdin administration rescued the prothrombotic phenotype in Hmox1-/- mice. Fifth, using a transcriptional analysis of arterial tissue, we found that HO-1 determined a transcriptional response to injury, with specific effects on cell cycle regulation, coagulation, thrombosis, and redox homeostasis. These data provide direct genetic evidence for a protective role of HO-1 against thrombosis and reactive oxygen species during vascular damage. Induction of HO-1 may be beneficial in the prevention of thrombosis associated with vascular oxidant stress and inflammation.

Pharmacokinetic bioequivalence of enfuvirtide using a needle-free device versus standard needle administration.

STUDY OBJECTIVES: To compare the relative bioavailability of enfuvirtide, a human immunodeficiency virus type 1 (HIV-1) fusion inhibitor, injected with the Biojector 2000 (B2000) needle-free device versus a 27-gauge half-inch needle-syringe; and to assess safety, tolerability, and patient preference for the two devices. DESIGN: Open-label, randomized, two-period crossover bioequivalence evaluation. SETTING: Clinical research center. PATIENTS: Twenty-seven adults with HIV-1 viral loads below 1000 copies/ml. INTERVENTION: Each patient received enfuvirtide 90 mg subcutaneously with the B2000 and with the needle-syringe, with a 1-week washout between treatments. MEASUREMENTS AND MAIN RESULTS: Twenty-six and 27 patients were included in the bioequivalence and safety analyses, respectively. Plasma enfuvirtide concentrations were measured at baseline and at several intervals after each injection. The B2000:needle-syringe ratios of maximum concentration (C(max)), area under the concentration-time curve from time zero extrapolated to infinity (AUC(0-infinity)), and AUC from time zero to tau (dosing interval) (AUC(0-tau)) served as criteria for bioequivalence determination. The two drug delivery systems were considered bioequivalent if the 90% confidence intervals (CIs) for the ratios were within 0.8-1.25. Safety and tolerability were evaluated based on documentation of adverse events, graded laboratory toxicities, and local injection-site reactions. Patient surveys provided feedback on device preference. Ratios of C(max), AUC(0-infinity), and AUC(0-tau) were 0.95 (90% CI 0.84-1.09), 0.99 (90% CI 0.93-1.05), and 0.99 (90% CI 0.93-1.05), respectively. The frequency of injection-site reactions was low, and severity was generally mild for both devices. Survey results showed 18 patients (69%) had a positive overall impression of the B2000 and 14 (54%) felt safer injecting with this device. Overall, 17 patients (65%) preferred the B2000 over the needle-syringe. CONCLUSION: Bioavailability of enfuvirtide with the B2000 and needle-syringe was equivalent based on C(max), AUC(0-tau), and AUC(0-infinity). Safety profiles and injection-site reactions were comparable between the devices, but patients preferred the B2000. Delivery of enfuvirtide with the B2000 is a feasible alternative to standard needle administration and warrants further evaluation.

A prospective clinical and pathological examination of injection site reactions with the HIV-1 fusion inhibitor enfuvirtide.

OBJECTIVE: Antiretroviral regimens containing the fusion inhibitor enfuvirtide (ENF) are associated with sustained viral suppression and immunological benefit. However, local injection site reactions (ISR) occur in the majority of patients. The aim of this study was to determine the pathogenesis of ISRs. METHODS: Injection sites were evaluated prospectively from 30 min up to 15-30 days post-injection in ENF-experienced (Cohort I) and ENF-naive patients (Cohort II) during the first 2 weeks of therapy. Four to five injections were given in rotating abdominal sites by a nurse using a standardized technique and were rigorously evaluated. RESULTS: Reactions were observed in 80-100% of patients; the majority of the reactions were mild to moderate, generally appeared within 24-48 h post-injection, and pain, induration and erythema were the most common clinical signs. Whereas most patients experienced ISRs, the overall prevalence in Cohort II was low (35% maximum). Punch biopsies of injection sites in Cohort I consisted primarily of mixed lymphocytic infiltrates with eosinophils and neutrophils. Injection vehicle (ENF buffer minus ENF) and reduced volume (2 x 0.5 ml ENF [45 mg] versus 1.0 ml [90 mg] ENF) were investigated in Cohort II. Fewer reactions appeared with vehicle and pain was absent with the smaller injection volume. Pathology was indistinguishable between ENF, vehicle and normal tissue in Cohort II patients. CONCLUSION: These results suggest that injection technique, injection volume and peptide may influence ISR to ENF.

Bone marrow-derived immune cells regulate vascular disease through a p27(Kip1)-dependent mechanism.

The cyclin-dependent kinase inhibitors are key regulators of cell cycle progression. Although implicated in carcinogenesis, they inhibit the proliferation of a variety of normal cell types, and their role in diverse human diseases is not fully understood. Here, we report that p27(Kip1) plays a major role in cardiovascular disease through its effects on the proliferation of bone marrow-derived (BM-derived) immune cells that migrate into vascular lesions. Lesion formation after mechanical arterial injury was markedly increased in mice with homozygous deletion of p27(Kip1), characterized by prominent vascular infiltration by immune and inflammatory cells. Vascular occlusion was substantially increased when BM-derived cells from p27(-/-) mice repopulated vascular lesions induced by mechanical injury in p27(+/+) recipients, in contrast to p27(+/+) BM donors. To determine the contribution of immune cells to vascular injury, transplantation was performed with BM derived from RAG(-/-) and RAG(+/+) mice. RAG(+/+) BM markedly exacerbated vascular proliferative lesions compared with what was found in RAG(-/-) donors. Taken together, these findings suggest that vascular repair and regeneration is regulated by the proliferation of BM-derived hematopoietic and nonhematopoietic cells through a p27(Kip1)-dependent mechanism and that immune cells largely mediate these effects.

cAMP targeting of p38 MAP kinase inhibits thrombin-induced NF-kappaB activation and ICAM-1 expression in endothelial cells.

We investigated the mechanisms by which elevated intracellular cAMP concentration inhibits the thrombin-induced ICAM-1 expression in endothelial cells. Exposure of human umbilical vein endothelial cells to forskolin or dibutyryl cAMP, which increase intracellular cAMP by separate mechanisms, inhibited the thrombin-induced ICAM-1 expression. This effect of cAMP was secondary to inhibition of NF-kappaB activity, the key regulator of thrombin-induced ICAM-1 expression in endothelial cells. The action of cAMP occurred downstream of IkappaBalpha degradation and was independent of NF-kappaB binding to the ICAM-1 promoter. We observed that cAMP interfered with thrombin-induced phosphorylation of NF-kappaB p65 (RelA) subunit, a crucial event promoting the activation of the DNA-bound NF-kappaB. Because p38 MAPK can induce transcriptional activity of RelA/p65 without altering the DNA binding function of NF-kappaB, we addressed the possibility that cAMP antagonizes thrombin-induced NF-kappaB activity and ICAM-1 expression by preventing the activation of p38 MAPK. We observed that treating cells with forskolin blocked the activation of p38 MAPK, and inhibition of p38 MAPK interfered with phosphorylation of RelA/p65 induced by thrombin. Our data demonstrate that increased intracellular cAMP concentration in endothelial cells prevents thrombin-induced ICAM-1 expression by inhibiting p38 MAPK activation, which in turn prevents phosphorylation of RelA/p65 and transcriptional activity of the bound NF-kappaB.

Galpha(q) and Gbetagamma regulate PAR-1 signaling of thrombin-induced NF-kappaB activation and ICAM-1 transcription in endothelial cells.

As thrombin binding to the G protein-coupled proteinase activated receptor-1 (PAR-1) induces endothelial adhesivity to leukocytes through NF-kappaB activation and intercellular adhesion molecule-1 (ICAM-1) expression, we determined the signaling pathways mediating the response. Studies showed that the heterotrimeric G proteins, Galpha(q), and the Gbetagamma dimer were key determinants of the PAR-1 agonist peptide (TFLLRNPNDK)-induced NF-kappaB activation and ICAM-1 expression in endothelial cells. Cotransfection of RGS3T, a regulator of G-protein signaling that inhibits Galpha(q), or alpha-transducin (Galpha(t)), a scavenger of the Gbetagamma, markedly decreased NF-kappaB activity induced by PAR-1 activation. We determined the downstream signaling targets activated by Galpha(q) and Gbetagamma that mediate NF-kappaB activation. Expression of the kinase-defective protein kinase C (PKC)-delta mutant inhibited NF-kappaB activation induced by the constitutively active Galpha(q) mutant, but had no effect on NF-kappaB activity induced by Gbeta(1)gamma(2). In related experiments, NF-kappaB as well as ICAM-1 promoter activation induced by Gbeta(1)gamma(2) were inhibited by the expression of the dominant-negative mutant of 85-kDa regulatory subunit of PI 3-kinase; however, the expression of this mutant had no effect on the response induced by activated Galpha(q). Cotransfection of the catalytically inactive Akt mutant inhibited the NF-kappaB activation induced by the constitutively active PI 3-kinase mutant as well as that by the activated forms of Galpha(q) and PKC-delta. These results support a model in which ligation of PAR-1 induces NF-kappaB activation and ICAM-1 transcription by the engagement of parallel Galphaq/PKC-delta and Gbetagamma/PI3-kinase pathways that converge at Akt.