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Hong Sun

Publications and source records attributed to Hong Sun.

99 records · Page 6Linked to original sources
PubMed2002

Use of recombinase activation gene-2 deficient mice to ascertain the role of cellular and humoral immune responses in the development of chronic rejection.

INTRODUCTION: Given its multifactorial etiology, the relative contribution of anti-donor cellular and humoral immune responses in the pathogenesis of chronic rejection is as yet ambiguous. We hypothesized that alloreactive T and B cells play a seminal role in the development of this lesion. METHODS: To address this hypothesis, RAG-2(-/-) mice were used as donors and recipients in a well-established murine model of aortic transplantation. Grafts were transplanted across the following groups: Group I: C3H --> C3H; Group II: Wild-type [WT] 129Sv (H-2(b)) --> C3H (H-2(k)); Group III: C3H --> WT 129Sv; Group IV: 129SvEv RAG-2(-/-) --> C3H; and Group V: C3H --> 129SvEv RAG-2(-/-). Grafts were harvested at d40 to 146 post-transplantation for morphologic and immunohistochemical analyses and semi-quantitative RT-PCR was employed to evaluate the intragraft mRNA expression of various immune mediators. Mixed lymphocyte reaction and complement-mediated alloantibody cytotoxicity assays were performed to determine anti-donor proliferative and humoral responses, respectively. RESULTS: Unlike that across the syngeneic combination (Group I), marked intimal thickening with corresponding luminal narrowing was observed in the majority of the aortic allografts (Groups II-IV). On the contrary, the morphology of C3H aortic allografts harvested from the majority of the RAG-2(-/-) was remarkably preserved. Correspondingly, anti-donor proliferative and humoral immune responses were undetectable in C3H --> RAG-2(-/-) recipients as was the intragraft mRNA expression of the Th(1) and the Th(2)-type cytokines. CONCLUSIONS: Taken together, these data suggest that in this murine model of aortic allotransplantation, donor-specific cellular and humoral responses play a dominant role in the initiation and perpetuation of chronic rejection.

Animals↗
PubMed2002

CAND1 binds to unneddylated CUL1 and regulates the formation of SCF ubiquitin E3 ligase complex.

The SCF ubiquitin E3 ligase regulates ubiquitin-dependent proteolysis of many regulatory proteins such as p27(Kip1), IkappaB, and beta-catenin. We report the isolation of a CUL1 binding protein, p120(CAND1). We found the majority of CUL1 is in a complex with CAND1 and ROC1 independent of SKP1 and F box protein SKP2. Both in vivo and in vitro, CAND1 prevents the binding of SKP1 and SKP2 to CUL1 while dissociation of CAND1 from CUL1 promotes the reverse reaction. Neddylation of CUL1 or the presence of SKP1 and ATP causes CAND1 dissociation. Our data suggest that CAND1 regulates the formation of the SCF complex, and its dissociation from CUL1 is coupled with the incorporation of F box proteins into the SCF complex, causing their destabilization.

Adenosine Triphosphate↗
PubMed2002

Cocaine metabolism accelerated by a re-engineered human butyrylcholinesterase.

Plasma butyrylcholinesterase (BChE) is important in the metabolism of cocaine, but natural human BChE has limited therapeutic potential for detoxication because of low catalytic efficiency with cocaine. Here we report pharmacokinetics of cocaine in rats treated with A328W/Y332A BChE, an excellent cocaine hydrolase designed with the aid of molecular modeling. Compared with wild-type BChE, this enzyme hydrolyzes cocaine with 40-fold improved k(cat) (154 min(-1) versus 4.1 min(-1)) and only slightly increased K(M) (18 microM versus 4.5 microM). In rats given this hydrolase (3 mg/kg i.v.) 10 min before cocaine challenge (6.8 mg/kg i.v.), cocaine half-life was reduced from 52 min to 18 min. Mirroring the reductions of plasma cocaine were large increases in benzoic acid, a product of BChE-mediated cocaine hydrolysis. All other pharmacokinetic parameters confirmed a large, dose-dependent acceleration of cocaine removal by the injected cocaine hydrolase. These results show that A328W/Y332A, an efficient cocaine hydrolase in vivo as well as in vitro, might promote cocaine detoxication in a clinical setting.

Amino Acid Substitution↗
PubMed2002

Re-engineering butyrylcholinesterase as a cocaine hydrolase.

To address the problem of acute cocaine overdose, we undertook molecular engineering of butyrylcholinesterase (BChE) as a cocaine hydrolase so that modest doses could be used to accelerate metabolic clearance of this drug. Molecular modeling of BChE complexed with cocaine suggested that the inefficient hydrolysis (k(cat) = 4 min(-1)) involves a rotation toward the catalytic triad, hindered by Tyr332. To eliminate rotational hindrance and retain substrate affinity, we introduced two amino acid substitutions (Ala328Trp/Tyr332Ala). The resulting mutant BChE reduced cocaine burden in tissues, accelerated plasma clearance by 20-fold, and prevented cocaine-induced hyperactivity in mice. The enzyme's kinetic properties (k(cat) = 154 min(-1), K(M) = 18 microM) satisfy criteria suggested previously for treating cocaine overdose (k(cat) >120 min(-1), K(M) < 30 microM). This success demonstrates that computationally guided mutagenesis can generate functionally novel enzymes with clinical potential.

Alanine↗
PubMed2002

Impairment of neuronal nitric oxide synthase-dependent dilation of cerebral arterioles during chronic alcohol consumption.

BACKGROUND: Although chronic alcohol consumption impairs endothelial nitric oxide synthase-dependent reactivity of cerebral arterioles, the effect of alcohol consumption on vasodilation in response to activation of neuronal nitric oxide synthase (nNOS) has not been examined. Thus, our first goal was to determine whether chronic alcohol consumption impairs nNOS-dependent reactivity of pial arterioles. Our second goal was to examine potential mechanisms for impaired responses of pial arterioles during chronic alcohol consumption. METHODS: Sprague Dawley rats were fed liquid diets with or without alcohol for 8 to 12 weeks. By using intravital microscopy, we measured the diameter of pial arterioles in response to nNOS-dependent agonists--NMDA and kainate (KA)--in the absence and presence of N(G)-monomethyl-L-arginine (L-NMMA) or 7-nitroindazole (7-NI). We also measured responses of pial arterioles to nitroglycerin. Next, using Western blot analysis, we measured protein levels of the NMDA receptor subunit, KA receptor subunit, and nNOS protein in cerebral microvessels, parietal cortex, cerebellum, and brainstem of non-alcohol-fed and alcohol-fed rats. RESULTS: Topical application of NMDA (100 and 300 microM) and KA (100 and 300 microM) produced dose-related dilation of pial arterioles in non-alcohol-fed and alcohol-fed rats. However, the magnitude of vasodilation in response to NMDA and KA, but not nitroglycerin, was significantly less in alcohol-fed compared with non-alcohol-fed rats. Topical application of L-NMMA (10 microM) or 7-NI (10 microM) significantly inhibited dilation of pial arterioles in response to NMDA and KA in non-alcohol-fed rats. In alcohol-fed rats, only NMDA-induced vasodilation was inhibited by L-NMMA. In addition, we found that NMDA receptor subunit and KA receptor subunit protein levels increased in the parietal cortex and cerebellum of alcohol-fed compared with non-alcohol-fed rats. However, no significant difference in protein level of nNOS was observed between non-alcohol-fed and alcohol-fed rats. CONCLUSIONS: Our findings suggest that chronic alcohol consumption impairs nNOS-dependent dilation of pial arterioles via a mechanism that appears to be unrelated to quantitative changes in NMDA receptors, KA receptors, or nNOS. Because the regulation of cerebral blood flow is influenced by neuronal activation, impaired reactivity of cerebral blood vessels to neuronal activation may contribute to the pathogenesis of cerebrovascular disorders observed during chronic alcohol consumption.

Alcohol Drinking↗
PubMed2002

[HAP-glutin-acetic acid coating on degradable polyamides implant].

Hydroxyapatite (HAP) formation on the surface of the degradable polyamides implant by a coating technology was studied. A suspension of HAP-glutin-acetic acid was prepared and brushed on the surface of the implant at room temperature. Scanning electron microscopy (SEM), X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FT-IR) were employed to study the composition and the microstructure of the coating. The results obtained indicate that the main composition of coating is crystal HAP, its structural formula is Ca10(PO4)6(OH)2. So the coating has bioactivity. The coating has also small pores, which can stimulate bone regrowth and adsorption of other bioactive materials or mediine. This technology is an effective method to improve medical performance of the polyamides implant.

Bone Substitutes↗
PubMedDate not supplied

In vivo properties of potassium channels in cerebral blood vessels during diabetes mellitus.

OBJECTIVE: While potassium (K+) channels are important in basal tone and dilatation of large and small cerebral vessels, the effect of diabetes mellitus on K+ channels remains unclear. The goal of this study was to identify the influence of diabetes on responses of cerebral vessels to inhibition/activation of K+ channels. METHODS: The authors measured in vivo responses of pial arterioles and the basilar artery to inhibition/activation of K+ channels in nondiabetic and diabetic rats using intravital microscopy. RESULTS: Pial arterioles from nondiabetic and diabetic rats constricted to barium chloride (BaCl2) and 4-aminopyridine (4-AP). However, the magnitude of vasoconstriction to BaCl2 was greater in nondiabetic than in diabetic rats. Tetraethylammonium (TEA) did not alter diameter of pial arterioles in nondiabetic or diabetic rats. In addition, dilatation of pial arterioles to KCl and NS-1619 was less in diabetic compared to nondiabetic rats. The basilar artery from nondiabetic and diabetic rats constricted in a similar manner to BaCl2 and 4-AP. In contrast, vasoconstriction to TEA was greater in diabetic than nondiabetic rats. Similar to that reported for pial arterioles, dilatation of the basilar artery to KCl and NS-1619 was less in diabetic than nondiabetic rats. CONCLUSIONS: Inward-rectifier (Kir) and voltage-dependent (Kv), but not calcium-activated (Kca), K+ channels are active under basal conditions in pial arterioles, while Kir, Kv, and Kca are active under basal conditions in the basilar artery of nondiabetic and diabetic rats. In addition, activation of Kir and Kca channels produces less cerebral vasodilatation in diabetic compared to nondiabetic rats. These findings provide new and important information regarding the influence of diabetes on the role of K+ channels in the regulation of cerebral vascular diameter.

Animals↗
PubMedDate not supplied

Inhibition of NAD(P)H oxidase alleviates impaired NOS-dependent responses of pial arterioles in type 1 diabetes mellitus.

OBJECTIVE: The goal was to identify the role of NAD(P)H oxidase in cerebrovascular dysfunction in type 1 diabetes mellitus (T1D). METHODS: In a first series of studies, rats were assigned to nondiabetic, diabetic (streptozotocin; 50 mg/kg IP), nondiabetic-apocynin (40 mg/kg/day in drinking water)-treated and diabetic-apocynin-treated groups. Two to three months later, the authors examined in vivo responses of pial arterioles to nitric oxide synthase (NOS)-dependent (acetylcholine and adenosine diphosphate (ADP)) and -independent (nitroglycerin) agonists. Next, they used Western blot analysis to examine protein levels for subunits of NAD(P)H oxidase in cerebral microvessels and parietal cortex tissue of nondiabetic and diabetic rats. Finally, they measured superoxide production by parietal cortex tissue in nondiabetic and diabetic rats. RESULTS: Acetylcholine- and ADP-induced dilatation of pial arterioles was impaired in diabetic compared to nondiabetic rats. In addition, while apocynin did not alter responses in nondiabetic rats, apocynin alleviated T1D-induced impairment of NOS-dependent vasodilatation. In addition, p47phox and gp91phox proteins were elevated in cerebral microvessels and parietal cortex tissue, respectively, of diabetic compared to nondiabetic rats. Further, basal production of superoxide was increased in diabetic compared to nondiabetic rats and apocynin decreased this basal production. CONCLUSIONS: The findings suggest that T1D impairs NOS-dependent reactivity of cerebral arterioles by a mechanism related to the formation of superoxide via activation of NAD(P)H oxidase.

Acetophenones↗