Poly-N-Acetyl Glucosamine (sNAG) Enhances Early Rotator Cuff Tendon Healing in a Rat Model.

Rotator cuff injuries frequently require surgical repairs which have a high failure rate. Biological augmentation has been utilized in an attempt to improve tendon repair. Poly-N-acetyl glucosamine (sNAG) polymer containing nanofibers has been shown to increase the rate for healing of venous leg ulcers. The purpose of this study was to investigate the healing and analgesic properties of sNAG in a rat rotator cuff injury and repair model. 144 adult male Sprague-Dawley rats underwent a transection and repair of their left supraspinatus tendons. Half of the animals received a sNAG membrane on the tendon-to-bone insertion site. Animals were further subdivided, receiving 1 or 3 days of analgesics. Animals were sacrificed 2, 4, or 8 weeks post-injury. Animals sacrificed at 4 and 8 weeks underwent longitudinal in vivo ambulatory assessment. Histological properties were assessed at 2, 4, and 8 weeks, and mechanical properties at 4 and 8 weeks. In the presence of analgesics, tendons receiving the sNAG polymer had significantly increased max load and max stress at 4 weeks, but not at 8 weeks. Ambulatory improvements were observed at 14 days in stride length and speed. Therefore, sNAG improves tendon-to-bone healing in a rat rotator cuff detachment and repair model.

Brincidofovir treatment of acyclovir-resistant disseminated varicella zoster virus infection in an immunocompromised host.

Brincidofovir (BCV) is a broad-spectrum antiviral agent active in vitro against double-stranded DNA viruses including herpesviruses, adenoviruses, polyomaviruses, and poxviruses. We report successful BCV use in management of disseminated acyclovir- and cidofovir-resistant varicella zoster virus in an immunocompromised hematopoietic stem cell transplant patient with chronic graft-versus-host disease who was intolerant to foscarnet.

Hypotensive mechanisms of amifostine.

Amifostine, a chemo- and radioprotective agent developed as adjunctive therapy for malignancies, induces hypotension after approximately 20% of patient administrations. This study examines the molecular mechanisms underlying hypotension induced by amifostine. Amifostine and its metabolite, WR-1065, induced dose-dependent hypotension in anesthetized rats that was not blocked by N(G)-methyl L arginine (L-NAME), an NO synthase inhibitor. WR-1065 but not amifostine induced concentration-dependent relaxation of isolated rat aortic rings in an endothelium-independent fashion. Relaxation was not associated with increases in cGMP or cAMP and could not be blocked by L-NAME or indomethacin. Similarly, neither amifostine or WR-1065 activated adenylyl, particulate guanylyl, or soluble guanylyl cyclases. WR-1065 relaxed rat aortic rings precontracted with norepinepherine, suggesting alpha-adrenergic blocking activity. However, neither amifostine nor WR-1065 altered the ability of prazosin or phentolamine to bind to alpha-adrenergic receptors. Further, WR-1065 had no effect on receptor-mediated increases in intracellular calcium in BAL 17 murine B lymphocytes in vitro. Thus, hypotension after administration of amifostine is mediated by WR-1065 and appears to result from direct relaxation of vascular smooth muscle. Smooth muscle relaxation induced by WR-1065 is not related to production of nitric oxide, prostaglandins, or cyclic nucleotides; alpha-adrenergic receptor antagonism; or interference with receptor-dependent increases in intracellular calcium. Administration of ephedrine, an efficacious adrenergic agonist, attenuated hypotension induced by amifostine in anesthetized rats and may be useful in alleviating hypotension associated with amifostine administration in patients.

Covalent binding of sulfamethoxazole reactive metabolites to human and rat liver subcellular fractions assessed by immunochemical detection.

Potentially serious idiosyncratic reactions associated with sulfamethoxazole (SMX) include systemic hypersensitivity reactions and hepatotoxicity. Covalent binding of SMX to proteins subsequent to its N-hydroxylation to form N4-hydroxysulfamethoxazole (SMX-HA) is thought to be involved in the pathogenesis of these reactions. A polyclonal antibody was elicited in rabbits against a SMX--keyhole limpet hemocyanin conjugate that recognized covalent protein adducts of SMX in microsomal protein and was used to characterize the covalent binding of SMX and its putative reactive metabolites to hepatic protein in vivo and in vitro. In vitro covalent binding of SMX to rat and human liver microsomal protein was NADPH-dependent, while binding of SMX-HA was not dependent on NADPH. SMX and SMX-HA produced similar patterns of covalent binding, with major protein targets in the region of 150, 100 (two bands), 70 (two bands), and 45-55 kDa. The pattern of covalent binding to human and rat liver microsomal protein was similar. Binding of SMX-HA was completely eliminated by GSH or by addition of cytosolic fractions and acetylcoenzyme A. The acetoxy metabolite of SMX also led to covalent binding, but it was primarily attributable to the formation of SMX-HA from acetoxySMX. In vivo exposure of rats to SMX did not result in detectable covalent binding by the methods employed. When rat liver slices were incubated with 2 mM SMX or 500 microM SMX-HA, no toxicity was observed and yet covalent binding of SMX-HA to 130, 100, 70, and 55 kDa proteins could be detected. These results confirm that covalent binding of SMX occurs via the formation of SMX-HA and that covalent binding of SMX-HA in vitro results from its conversion to the more reactive nitroso metabolite. Acetylation of SMX-HA protected against its covalent binding. Further studies are required to determine how this in vitro covalent binding relates to in vivo covalent binding in humans and to either direct or immune-mediated cytotoxicity in SMX idiosyncratic drug reactions.

Further investigations of the role of acetylation in sulphonamide hypersensitivity reactions.

Abstract Sulphonamide hypersensitivity reactions are believed to be mediated through reactive intermediates derived from oxidation of the paraamino group to form sulphonamide hydroxylamines. Sulphamethoxazole hydroxylamine (SMX-HA) can be acetylated by N-acetyltransferase (NAT) enzymes to form an acetoxy metabolite (acetoxySMX). In the current studies, acetoxySMX was found to be not toxic over the concentration range of 0 to 500 µM towards a human lymphoblastoid cell line (RPMI 1788) or a human hepatoma cell line (HepG2). Further, transient expression of NAT1 in COS-1 cells or stable transfection of NAT1 andNAT2 in HepG2 cells did not alter the toxicity of SMX-HA in vitro. The activity of NAT1 in isolated mononuclear leucocytes (a reflection of systemic NAT1 activity) determined with paraaminobenzoic acid as a substrate was not different between controls (n = 11) or patients with a known hypersensitivity reaction (n = 5) (4.1 ±1.2 nmol min(-1)mg(-1) vs 5.7 ± 1.4 nmol min(-1) mg(-1)). Thus, acetoxy SMX is unlikely to play a significant role in mediating SMX hypersensitivity reactions anda constitutive deficiency in NAT1 activity is not a common finding in patients susceptible to SMX hypersensitivity reactions.

Cardioprotective effect of insulin-like growth factor I in myocardial ischemia followed by reperfusion.

In the present study, the cardioprotective effects of insulin-like growth factor I (IGF-I) were examined in a murine model of myocardial ischemia reperfusion (i.e., 20 min + 24 hr). IGF-I (1-10 micrograms per rat) administered 1 hr prior to ischemia significantly attenuated myocardial injury (i.e., creatine kinase loss) compared to vehicle (P < 0.001). In addition, cardiac myeloperoxidase activity, an index of neutrophil accumulation, in the ischemic area was significantly attenuated by IGF-I (P < 0.001). This protective effect of IGF-I was not observed with des-(1-3)-IGF-I. Immunohistochemical analysis of ischemic-reperfused myocardial tissue demonstrated markedly increased DNA fragmentation due to programmed cell death (i.e., apoptosis) compared to nonischemic myocardium. Furthermore, IGF-I significantly attenuated the incidence of myocyte apoptosis after myocardial ischemia and reperfusion. Therefore, IGF-I appears to be an effective agent for preserving ischemic myocardium from reperfusion injury and protects via two different mechanisms--inhibition of polymorphonuclear leukocyte-induced cardiac necrosis and inhibition of reperfusion-induced apoptosis of cardiac myocytes.

Antipeptide antibodies against overlapping sequences differentially inhibit human CYP2D6.

Two peptides that correspond to sequences within the major 33-amino acid sequence recognized by human liver-kidney microsomal-1 autoantibodies were used to elicit antibodies in rabbits (four per peptide) against CYP2D6. Peptide 1(DPAQPPRDLTEAFLA) corresponded to amino acids 263-277, and peptide 2 (LLTEHRMTWDPAQPPRDLTE) corresponded to amino acids 254-273 of CYP2D6. The peptide-keyhole limpet hemocyanin conjugates elicited good immune responses against their respective peptides as judged by enzyme-linked immunosorbent assay (titers of 1/10,000 to 1/30,000). The antisera recognized CYP2D6 on Western blots and, to varying extents, inhibited recombinant CYP2D6 and liver microsomal CYP2D6 activity. Immunization with peptide 2 produced antisera with the greatest inhibitory potency. Antiserum from a rabbit (#236) immunized with peptide 2 inhibited up to 95% of dextromethorphan O-demethylase activity in human liver microsomes at the highest concentration tested (40% v/v) but did not significantly inhibit CYP1A2, CYP2C9, CYP2E1, or CYP3A4 marker activities. On Western blot, only a single immunoreactive protein comigrating with recombinant CYP2D6 was recognized. In liver microsomes from a CYP2D6-deficient individual, no proteins were recognized, and the antisera did not cross-react with recombinant CYP1A2, CYP2C9, CYP2E1, or CYP3A4. There was a significant correlation between the quantity of immunoreactive CYP2D6 as determined by immunoblotting with anti-peptide 2 antiserum and dextromethorphan O-demethylation in a panel of 10 human liver microsomes (r = 0.95). These data identify a peptide sequence (peptide 2) that can be used to raise antisera that specifically recognize and inhibit CYP2D6.

Beneficial effects of oligotide, a novel oligodeoxyribonucleotide, in murine traumatic shock.

The effects of oligotide, an oligodeoxyribonucleotide analog, were investigated in an experimental model of traumatic shock. Pentobarbital-anesthetized rats subjected to Noble-Collip drum trauma and receiving only the vehicle (i.e., Krebs-Henseleit solution) developed a severe form of traumatic shock characterized by marked hypotension (61 +/- 6 mmHg), a survival time of 115 +/- 21 min, endothelial dysfunction, significant increases in plasma free amino-nitrogen concentration (p < .001) as well as elevated intestinal myeloperoxidase activity. In contrast, oligotide given intravenously (15 mg/kg bolus + 10 mg/kg/h infusion for 5 h) resulted in a significant prolongation of survival time to 209 +/- 31 min (p < .01), a significant and sustained increase in mean arterial blood pressure, a significant attenuation of plasma free amino-nitrogen concentration (p < .01), and intestinal myeloperoxidase activity (p < .05). Furthermore, oligotide significantly preserved superior mesenteric artery (SMA) endothelial function as seen by the relaxation response of isolated SMA rings to acetylcholine (71 +/- 5% vs. 36 +/- 5%, p < .01 compared to untreated trauma rats). Moreover, oligotide in a concentration-dependent manner attenuated unstimulated human neutrophil adherence to either thrombin or trauma-activated SMA endothelium in vitro (p < .001). Thus, our data suggest that the mechanism of the protective effect of oligotide in traumatic shock is improving endothelial function and diminishing neutrophil accumulation leading to reduced tissue injury.