Synthesis and evaluation of [18F]Fluorobutyl ethacrynic amide: a potential PET tracer for studying glutathione transferase

[(18)F]Flurobutyl ethacrynic amide ([(18)F]FBuEA) was prepared from the precursor tosylate N-Boc-N-[4-(toluenesulfonyloxy)butyl]ethacrynic amide with a radiochemical yield of 3%, a specific activity of 48 GBq/μmol and radiochemical purity of 98%. Chemical conjugation of [(18)F]FBuEA with glutathione (GSH) via a self-coupling reaction and enzymatic conjugation under catalysis of glutathiontransferase alpha (GST-α) and π provided about 41% yields of radiochemical conjugated product [(18)F]FBuEA-GSH, 85% and 5-16%, respectively. The catalytic selectivity of this tracer toward GST-alpha was addressed. Positron emission tomography (PET) imaging of [(18)F]FBuEA in normal rats showed that a homogeneous pattern of radioactivity was distributed in the liver, suggesting a catalytic role of GST. By contrast, PET images of [(18)F]FBuEA in rats with thioacetamide-induced cholangiocarcinoma displayed a heterogeneous pattern of radioactive accumulation with cold spots in tumor lesions. PET imaging with [(18)F]FBuEA could be used for early diagnosis of hepatic tumor with a low GST activity as well as liver function.     

Whole blood-derived microRNA signatures in mice exposed to lipopolysaccharides

Background

Lipopolysaccharide (LPS) is recognized as the most potent microbial mediator presaging the threat of invasion of Gram-negative bacteria that implicated in the pathogenesis of sepsis and septic shock. This study was designed to examine the microRNA (miRNA) expression in whole blood from mice injected with intraperitoneal LPS.

Methods

C57BL/6 mice received intraperitoneal injections of varying concentrations (range, 10–1000 μg) of LPS from different bacteria, including Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa, Salmonella enterica, and Serratia marcescens and were killed 2, 6, 24, and 72 h after LPS injection. Whole blood samples were obtained and tissues, including lung, brain, liver, and spleen, were harvested for miRNA expression analysis using an miRNA array (Phalanx miRNA OneArray® 1.0). Upregulated expression of miRNA targets in the whole blood of C57BL/6 and Tlr4^−/− mice injected with LPS was quantified using real-time RT-PCR and compared with that in the whole blood of C57BL/6 mice injected with lipoteichoic acid (LTA) from Staphylococcus aureus.

Results

Following LPS injection, a significant increase of 15 miRNAs was observed in the whole blood. Among them, only 3 miRNAs showed up-regulated expression in the lung, but no miRNAs showed a high expression level in the other examined tissues. Upregulated expression of the miRNA targets (let-7d, miR-15b, miR-16, miR-25, miR-92a, miR-103, miR-107 and miR-451) following LPS injection on real-time RT-PCR was dose- and time-dependent. miRNA induction occurred after 2 h and persisted for at least 6 h. Exposure to LPS from different bacteria did not induce significantly different expression of these miRNA targets. Additionally, significantly lower expression levels of let-7d, miR-25, miR-92a, miR-103, and miR-107 were observed in whole blood of Tlr4^−/− mice. In contrast, LTA exposure induced moderate expression of miR-451 but not of the other 7 miRNA targets.

Conclusions

We identified a specific whole blood–derived miRNA signature in mice exposed to LPS, but not to LTA, from different gram-negative bacteria. These whole blood-derived miRNAs are promising as biomarkers for LPS exposure.     

Microglia recognize double-stranded RNA via TLR3

Microglia are CNS resident innate immune cells of myeloid origin that become activated and produce innate proinflammatory molecules upon encountering bacteria or viruses. TLRs are a phylogenetically conserved diverse family of sensors for pathogen-associated molecular patterns that drive innate immune responses. We have recently shown that mice deficient in TLR3 (TLR3(-/-) mice) are resistant to lethal encephalitis and have reduced microglial activation after infection with West Nile virus, a retrovirus that produces dsRNA. We wished to determine whether microglia recognize dsRNA through the TLR3 pathway. In vitro, murine wild-type primary cultured microglia responded to synthetic dsRNA polyinosinic-polycytidylic acid (poly(I:C)) by increasing TLR3 and IFN-beta mRNA and by morphologic activation. Furthermore, wild-type microglia dose dependently secreted TNF-alpha and IL-6 after poly(I:C) challenge, whereas TLR3(-/-) microglia produced diminished cytokines. Activation of MAPK occurred in a time-dependent fashion following poly(I:C) treatment of wild-type microglia, but happened with delayed kinetics in TLR3(-/-) microglia. As an in vivo model of encephalitis, wild-type or TLR3(-/-) mice were injected intracerebroventricularly with poly(I:C) or LPS, and microglial activation was assessed by cell surface marker or phospho-MAPK immunofluorescence. After intracerebroventricular injection of poly(I:C), microgliosis was clearly evident in wild-type mice but was nearly absent in TLR3(-/-) animals. When taken together, our results demonstrate that microglia recognize dsRNA through TLR3 and associated signaling molecules and suggest that these cells are key sensors of dsRNA-producing viruses that may invade the CNS.     

Thrombin induces cyclooxygenase‐2 expression and prostaglandin E2 release via PAR1 activation and ERK1/2‐ and p38 MAPK‐dependent pathway in murine macrophages

Thrombin levels increase at sites of vascular injury and during acute coronary syndromes. It is also increased several fold by sepsis with a reciprocal decrease in the anti‐thrombin III levels. In this study we investigate the effects of thrombin on the induction of cyclooxygenase‐2 (COX‐2) and prostaglandin (PG) production in macrophages. Thrombin‐induced COX‐2 protein and mRNA expression in RAW264.7 and primary cultured peritoneal macrophages. A serine proteinase, trypsin, also exerted a similar effect. The inducing effect by thrombin in macrophages was not affected by a lipopolysaccharide (LPS)‐binding antibiotic, polymyxin B, excluding the possibility of LPS contamination. The increase of COX‐2 expression by thrombin was functionally linked to release of PGE₂ and PGI₂ but not thromboxane A₂ into macrophage culture medium. Thrombin‐induced COX‐2 expression and PGE₂ production were significantly attenuated by PD98059 and SB202190 but not by SP600125, suggesting that ERK1/2 and p38 MAPK activation were involved in this process. This was supported by the observation that thrombin could directly activate ERK1/2 and p38 MAPK in macrophages. A further analysis indicated that the proteinase‐activated receptor 1 (PAR1)‐activating agonist induced effects similar to those induced by thrombin in macrophages and the PAR1 antagonist‐SCH79797 could attenuate thrombin‐induced COX‐2 expression and PGE₂ release. Taken together, we provided evidence demonstrating that thrombin can induce COX‐2 mRNA and protein expression and PGE₂ production in macrophages through PAR1 activation and ERK1/2 and p38 MAPK‐dependent pathway. The results presented here may explain, at least in part, the possible contribution of thrombin and macrophages in these pathological conditions. J. Cell. Biochem. 108: 1143–1152, 2009. © 2009 Wiley‐Liss, Inc.     

Resonant X-Ray Scattering and Absorption for the Global and Local Structures of Cu-modified Metallothioneins in Solution

With Cd and Zn metal ions removed from the native rabbit-liver metallothionein upon unfolding, Cu-modified metallothioneins (Cu-MTs) were obtained during refolding in solutions containing Cu^I or Cu^II ions. X-ray absorption near-edge spectroscopic results confirm the respectively assigned oxidation states of the copper ions in Cu^I-MT and Cu^II-MT. Global and local structures of the Cu-MTs were subsequently characterized by anomalous small-angle x-ray scattering (ASAXS) and extended x-ray absorption fine structure. Energy-dependent ASAXS results indicate that the morphology of Cu^II-MT resembles that of the native MT, whereas Cu^I-MT forms oligomers with a higher copper content. Both dummy-residue simulation and model-shape fitting of the ASAXS data reveal consistently rodlike morphology for Cu^II-MT. Clearly identified Cu-S, Cu-O, and Cu-Cu contributions in the extended x-ray absorption fine structure analysis indicate that both Cu^I and Cu^II ions are bonded with O and S atoms of nearby amino acids in a four-coordination environment, forming metal clusters smaller than metal thiolate clusters in the native MT. It is demonstrated that a combination of resonant x-ray scattering and x-ray absorption can be particularly useful in revealing complementary global and local structures of metalloproteins due to the atom specific characteristics of the two techniques.     

The discovery of potent inhibitors of aldosterone synthase that exhibit selectivity over 11-β-hydroxylase

Aldosterone, the final component of the renin–angiotensin–aldosterone system, plays an important role in the pathophysiology of hypertension and congestive heart failure. Aldosterone synthase (CYP11B2) catalyzes the last three steps of aldosterone biosynthesis, and as such appears to be a target for the treatment of these disorders. A sulfonamide–imidazole scaffold has proven to be a potent inhibitor of CYP11B2. Furthermore, this scaffold can achieve high levels of selectivity for CYP11B2 over CYP11B1, a key enzyme in the biosynthesis of cortisol.     

Directed evolution of a thermostable quorum-quenching lactonase from the amidohydrolase superfamily

A thermostable quorum-quenching lactonase from Geobacillus kaustophilus HTA426 (GI: 56420041) was used as an initial template for in vitro directed evolution experiments. This enzyme belongs to the phosphotriesterase-like lactonase (PLL) group of enzymes within the amidohydrolase superfamily that hydrolyze N-acylhomoserine lactones (AHLs) that are involved in virulence pathways of quorum-sensing pathogenic bacteria. Here we have determined the N-butyryl-l-homoserine lactone-liganded structure of the catalytically inactive D266N mutant of this enzyme to a resolution of 1.6 Å. Using a tunable, bioluminescence-based quorum-quenching molecular circuit, the catalytic efficiency was enhanced, and the AHL substrate range increased through two point mutations on the loops at the C-terminal ends of the third and seventh β-strands. This E101N/R230I mutant had an increased value of k_cat/K_m of 72-fold toward 3-oxo-N-dodecanoyl-l-homoserine lactone. The evolved mutant also exhibited lactonase activity toward N-butyryl-l-homoserine lactone, an AHL that was previously not hydrolyzed by the wild-type enzyme. Both the purified wild-type and mutant enzymes contain a mixture of zinc and iron and are colored purple and brown, respectively, at high concentrations. The origin of this coloration is suggested to be because of a charge transfer complex involving the β-cation and Tyr-99 within the enzyme active site. Modulation of the charge transfer complex alters the lactonase activity of the mutant enzymes and is reflected in enzyme coloration changes. We attribute the observed enhancement in catalytic reactivity of the evolved enzyme to favorable modulations of the active site architecture toward productive geometries required for chemical catalysis.     

Differential change in expression of pulmonary ET-1 and eNOS in rats after chronic left ventricular pressure overload

Pressure overload in the left ventricle of the heart follows a chronic and progressive course, resulting in eventual left heart failure and pulmonary hypertension (PH). The purpose of this research was to determine whether a differential pulmonary gene change of endothelin (ET)-1 and endothelial nitric oxide synthase (eNOS) occurred in adult rats with left ventricular overload. Eight groups of eight rats each were used (four rats with banding and four rats with sham operations). The rats underwent ascending aortic banding for 1 day, 2 weeks, 4 weeks, and 12 weeks before sacrifice. Significant medial hypertrophy of the pulmonary arterioles developed in two groups (4 and 12 weeks). Increased pulmonary arterial pressures were noted in three groups (1 day, 4 weeks, and 12 weeks). The aortic banding led to significant increases in pulmonary preproET-1 messenger RNA (mRNA) at 1 day and 12 weeks, and in pulmonary eNOS mRNA at 1 day and 12 weeks. In addition, there was increased pulmonary eNOS content at 1 day and 12 weeks in the banded rats, and increased lung cGMP levels were observed at 1 day. Increased lung ET-1 levels were also noted at 1 day (banded, 310 +/- 12 ng/g protein; sham, 201 +/- 12 ng/g protein; P < 0.01), 4 weeks (banded, 232 +/- 12 ng/g protein; sham, 201 +/- 12 ng/g protein; P < 0.01) and 12 weeks (banded, 242 +/- 12 ng/g protein; sham, 202 +/- 12 ng/g protein; P < 0.01). This indicates that the upregulated expression of ET-1 developed at least 4 weeks before eNOS expression in the course of PH, and, thus, medication against ET-1 could play a crucial role in treating PH with cardiac dysfunction secondary to aortic banding.     

The hemodynamic and metabolic profiles of Zucker diabetic fatty rats treated with a single molecule triple vasopeptidase inhibitor, CGS 35601

CGS 35601 is a triple vasopeptidase inhibitor (VPI) of angiotensin converting enzyme (ACE), neutral endopeptidase (NEP), and endothelin (ET) converting enzyme-1 (ECE-1), with respective IC(50) values of 22, 2, and 55 nM. The aim of the present study was to establish the hemodynamic profile of Zucker diabetic fatty (Zdf)-Fatty rats, a high-fat diet gene-prone model developing spontaneous Type 2 diabetes (T2D) and the effects of CGS 35601. Male Zdf-Fatty (14 weeks, n = 17-23), Zdf-Lean (14 weeks, n = 8-10), and Wistar (14 weeks, n = 9-10) rats on distinct diets were implanted with a catheter in the left carotid and placed individually in a metabolic cage for 30 days. The hemodynamic profile and some metabolic biomarkers were assessed daily. After a 7-day stabilization period, the Zdf-Fatty rats were divided into two groups: Group 1, controls (n = 7-10) receiving vehicle-saline (250 microl/hr) and Group 2, (n = 10-13) receiving increasing doses of CGS 35601 (0.1, 1, and 5 mg/kg/day x 6 days each, intra-arterially) followed by a 5-day washout period. Mean arterial blood pressure (MABP) of young Zdf-Fatty rats was compared with age-matched Zdf-Lean and Wistar rats, which were found similar. MABP decreased by 5.9% (from baseline at 102 +/- 5 to 96 +/- 4 mmHg), 12.7% (to 89 +/- 6 mmHg) and 21.6% (to 80 +/- 4 mmHg), at 0.1, 1, and 5 mg/kg/day, respectively, in CGS 35601-treated Zdf-Fatty rats. Systolic and diastolic blood pressures were similarly reduced. The heart rate was not affected. Hyperglycemic status and insulin-resistance were not modulated by short-term treatment. CGS 35601 presented an excellent short-term safety profile. This novel molecule and class of VPI may be of interest for lowering vascular tone. Further long-term studies, once cardiovascular and renal complications have developed in this T2D rat model are warranted to define the efficacy of this class of VPI.