Tristetraprolin Mediates Radiation-Induced TNF-α Production in Lung Macrophages

The efficacy of radiation therapy for lung cancer is limited by radiation-induced lung toxicity (RILT). Although tumor necrosis factor-alpha (TNF-α) signaling plays a critical role in RILT, the molecular regulators of radiation-induced TNF-α production remain unknown. We investigated the role of a major TNF-α regulator, Tristetraprolin (TTP), in radiation-induced TNF-α production by macrophages. For in vitro studies we irradiated (4 Gy) either a mouse lung macrophage cell line, MH-S or macrophages isolated from TTP knockout mice, and studied the effects of radiation on TTP and TNF-α levels. To study the in vivo relevance, mouse lungs were irradiated with a single dose (15 Gy) and assessed at varying times for TTP alterations. Irradiation of MH-S cells caused TTP to undergo an inhibitory phosphorylation at Ser-178 and proteasome-mediated degradation, which resulted in increased TNF-α mRNA stabilization and secretion. Similarly, MH-S cells treated with TTP siRNA or macrophages isolated from ttp (−/−) mice had higher basal levels of TNF-α, which was increased minimally after irradiation. Conversely, cells overexpressing TTP mutants defective in undergoing phosphorylation released significantly lower levels of TNF-α. Inhibition of p38, a known kinase for TTP, by either siRNA or a small molecule inhibitor abrogated radiation-induced TNF-α release by MH-S cells. Lung irradiation induced TTP^Ser178 phosphorylation and protein degradation and a simultaneous increase in TNF-α production in C57BL/6 mice starting 24 h post-radiation. In conclusion, irradiation of lung macrophages causes TTP inactivation via p38-mediated phosphorylation and proteasome-mediated degradation, leading to TNF-α production. These findings suggest that agents capable of blocking TTP phosphorylation or stabilizing TTP after irradiation could decrease RILT.     

Improving the robustness of a low-cost insect cell medium for baculovirus biopesticides production, via hydrolysate streamlining using a tube bioreactor-based statistical optimization routine

A critical component of an in vitro production process for baculovirus biopesticides is a growth medium that is efficacious, robust, and inexpensive. An in‐house low‐cost serum‐free medium, VPM3, has been shown to be very promising in supporting Helicoverpa armigera nucleopolyhedrovirus (HaSNPV) production in H. zea insect cell suspension cultures, for use as a biopesticide against the Heliothine pest complex. However, VPM3 is composed of a significant number of undefined components, including five different protein hydrolysates, which introduce a challenging lot‐to‐lot variability to the production process. In this study, an intensive statistical optimization routine was employed to reduce the number of protein hydrolysates in VPM3 medium. Nearly 300 runs (including replicates) were conducted with great efficiency by using 50 mL TubeSpin® bioreactors to propagate insect cell suspension cultures. Fractional factorial experiments were first used to determine the most important of the five default protein hydrolysates, and to screen for seven potential substitutes for the default meat peptone, Primatone RL. Validation studies informed by the screening tests showed that promising alternative media could be formulated based on just two protein hydrolysates, in particular the YST‐AMP (Yeast Extract and Amyl Meat Peptone) and YST‐POT (Yeast Extract and Lucratone Potato Peptone) combinations. The YST‐AMP (meat‐based) and YST‐POT (meat‐free) variants of VPM3 were optimized using response surface methodology, and were shown to be just as good as the default VPM3 and the commercial Sf‐900 II media in supporting baculovirus yields, hence providing a means toward a more reproducible and scalable production process for HaSNPV biopesticides. © 2012 American Institute of Chemical Engineers Biotechnol. Prog.,, 2012     

Dysregulated zinc and sphingosine-1-phosphate signaling in pulmonary hypertension: Potential effects by targeting of bone morphogenetic protein receptor type 2 in pulmonary microvessels

Recently identified molecular targets in pulmonary artery hypertension (PAH) include sphingosine-1-phosphate (S1P) and zinc transporter ZIP12 signaling. This study sought to determine linkages between these pathways, and with BMPR2 signaling. Lung tissues from a rat model of monocrotaline-induced PAH and therapeutic treatment with bone marrow–derived endothelial-like progenitor cells transduced to overexpress BMPR2 were studied. Multifluorescence quantitative confocal microscopy (MQCM) was applied for analysis of protein expression and localization of markers of vascular remodeling (αSMA and BMPR2), parameters of zinc homeostasis (zinc transporter SLC39A/ZIP family members 1, 10, 12 and 14; and metallothionein MT3) and S1P extracellular signaling (SPHK1, SPNS2, S1P receptor isoforms 1, 2, 3, 5) in 20–200 µm pulmonary microvessels. ZIP12 expression in whole lung tissue lysates was assessed by western blot. Spearman nonparametric correlations between MQCM readouts and hemodynamic parameters, Fulton index (FI), and right ventricular systolic pressure (RVSP) were measured. In line with PAH status, pulmonary microvessels in monocrotaline-treated animals demonstrated significant (p < .05, n = 6 per group) upregulation of αSMA (twofold) and downregulation of BMPR2 (20%). Upregulated ZIP12 (92%), MT3 (57.7%), S1PR2 (54.8%), and S1PR3 (30.3%) were also observed. Significant positive and negative correlations were demonstrated between parameters of zinc homeostasis (ZIP12, MT3), S1P signaling (S1PRs, SPNS2), and vascular remodeling (αSMA, FI, RVSP). MQCM and western blot analysis showed that monocrotaline-induced ZIP12 upregulation could be partially negated by BMPR2-targeted therapy. Our results indicate that altered zinc transport/storage and S1P signaling in the monocrotaline-induced PAH rat model are linked to each other, and could be alleviated by BMPR2-targeted therapy.     

Azole-resistant Aspergillus fumigatus is highly prevalent in the environment of Vietnam,with marked variability by land use type

Azole-resistant environmental Aspergillus fumigatus presents a threat to public health but the extent of this threat in Southeast Asia is poorly described. We conducted environmental surveillance in the Mekong Delta region of Vietnam, collecting air and ground samples across key land-use types, and determined antifungal susceptibilities of Aspergillus section Fumigati (ASF) isolates and azole concentrations in soils. Of 119 ASF isolates, 55% were resistant (or non-wild type) to itraconazole, 65% to posaconazole and 50% to voriconazole. Azole resistance was more frequent in A. fumigatus sensu stricto isolates (95%) than other ASF species (32%). Resistant isolates and agricultural azole residues were overrepresented in samples from cultivated land. cyp51A gene sequence analysis showed 38/56 resistant A. fumigatus sensu stricto isolates carried known resistance mutations, with TR₃₄/L98H most frequent (34/38).     

The Respiratory Syncytial Virus Matrix Protein Possesses a Crm1-Mediated Nuclear Export Mechanism

The respiratory syncytial virus (RSV) matrix (M) protein is localized in the nucleus of infected cells early in infection but is mostly cytoplasmic late in infection. We have previously shown that M localizes in the nucleus through the action of the importin β1 nuclear import receptor. Here, we establish for the first time that M''s ability to shuttle to the cytoplasm is due to the action of the nuclear export receptor Crm1, as shown in infected cells, and in cells transfected to express green fluorescent protein (GFP)-M fusion proteins. Specific inhibition of Crm1-mediated nuclear export by leptomycin B increased M nuclear accumulation. Analysis of truncated and point-mutated M derivatives indicated that Crm1-dependent nuclear export of M is attributable to a nuclear export signal (NES) within residues 194 to 206. Importantly, inhibition of M nuclear export resulted in reduced virus production, and a recombinant RSV carrying a mutated NES could not be rescued by reverse genetics. That this is likely to be due to the inability of a nuclear export deficient M to localize to regions of virus assembly is indicated by the fact that a nuclear-export-deficient GFP-M fails to localize to regions of virus assembly when expressed in cells infected with wild-type RSV. Together, our data suggest that Crm1-dependent nuclear export of M is central to RSV infection, representing the first report of such a mechanism for a paramyxovirus M protein and with important implications for related paramyxoviruses.The Pneumovirus respiratory syncytial virus (RSV) within the Paramyxoviridae family is the most common cause of lower-respiratory-tract disease in infants (7). The negative-sense single-strand RNA genome of RSV encodes two nonstructural and nine structural proteins, comprising the envelope glycoproteins (F, G, and SH), the nucleocapsid proteins (N, P, and L), the nucleocapsid-associated proteins (M2-1 and M2-2), and the matrix (M) protein (1, 7, 11). Previously, we have shown that M protein localizes in the nucleus at early stages of infection, but later in infection it is localized mainly in the cytoplasm, in association with nucleocapsid-containing cytoplasmic inclusions (13, 16). The M proteins of other negative-strand viruses, such as Sendai virus, Newcastle disease virus, and vesicular stomatitis virus (VSV), have also been observed in the nucleus at early stages of infection (32, 40, 48). Interestingly, the M proteins of all of these viruses, including RSV, play major roles in virus assembly, which take place in the cytoplasm and at the cell membrane (11, 12, 24, 34, 36, 39), but the mechanisms by which trafficking between the nucleus and cytoplasm occurs are unknown.The importin β family member Crm1 (exportin 1) is known to mediate nuclear export of proteins bearing leucine-rich nuclear export signals (NES) (8, 9, 18, 19, 37, 42, 43), such as the human immunodeficiency virus type 1 Rev protein (4). In the case of the influenza virus matrix (M1) protein, binding to the influenza virus nuclear export protein, which possesses a Crm1-recognized NES, appears to be responsible for its export from the nucleus, bound to the influenza virus RNA (3).We have recently shown that RSV M localizes in the nucleus through a conventional nuclear import pathway dependent on the nuclear import receptor importin β1 (IMPβ1) and the guanine nucleotide-binding protein Ran (14). In the present study, we show for the first time that RSV M possesses a Crm1-dependent nuclear export pathway, based on experiments using the specific inhibitor leptomycin B (LMB) (25), both in RSV-infected cells and in green fluorescent protein (GFP)-M fusion protein-expressing transfected cells. We use truncated and point-mutated M derivatives to map the Crm1-recognized NES within the M sequence and show that Crm1-dependent nuclear export is critical to the RSV infectious cycle, since LMB treatment early in infection, inhibiting M export from the nucleus, reduces RSV virion production and a recombinant RSV carrying a NES mutation in M was unable to replicate, probably because M deficient in nuclear export could not localize to areas of virus assembly, as shown in RSV-infected cells transfected to express GFP-M. This is the first report of a Crm1-mediated nuclear export pathway for a paramyxovirus M protein, with implications for the trafficking and function of other paramyxovirus M proteins.     

Cost-Effectiveness Analysis of Six Strategies to Treat Recurrent Clostridium difficile Infection

Objective

To assess the cost-effectiveness of six treatment strategies for patients diagnosed with recurrent Clostridium difficile infection (CDI) in Canada: 1. oral metronidazole; 2. oral vancomycin; 3.oral fidaxomicin; 4. fecal transplantation by enema; 5. fecal transplantation by nasogastric tube; and 6. fecal transplantation by colonoscopy.

Perspective

Public insurer for all hospital and physician services.

Setting

Ontario, Canada.

Methods

A decision analytic model was used to model costs and lifetime health effects of each strategy for a typical patient experiencing up to three recurrences, over 18 weeks. Recurrence data and utilities were obtained from published sources. Cost data was obtained from published sources and hospitals in Toronto, Canada. The willingness-to-pay threshold was $50,000/QALY gained.

Results

Fecal transplantation by colonoscopy dominated all other strategies in the base case, as it was less costly and more effective than all alternatives. After accounting for uncertainty in all model parameters, there was an 87% probability that fecal transplantation by colonoscopy was the most beneficial strategy. If colonoscopy was not available, fecal transplantation by enema was cost-effective at $1,708 per QALY gained, compared to metronidazole. In addition, fecal transplantation by enema was the preferred strategy if the probability of recurrence following this strategy was below 8.7%. If fecal transplantation by any means was unavailable, fidaxomicin was cost-effective at an additional cost of $25,968 per QALY gained, compared to metronidazole.

Conclusion

Fecal transplantation by colonoscopy (or enema, if colonoscopy is unavailable) is cost-effective for treating recurrent CDI in Canada. Where fecal transplantation is not available, fidaxomicin is also cost-effective.     

A fluorescent reporter assay for the detection of ligands acting through Gi protein-coupled receptors

Accompanying the advances in basic biology of G protein-coupled receptors (GPCRs) is the practical need among biopharmaceutical companies for sensitive assays to assess GPCR function, particularly formats that are compatible with high-throughput drug screening. Here we describe a novel cell-based assay format for the high-throughput detection of ligands for Gi protein-coupled receptors. Two Gi-GPCRs, mu-opioid receptor (mu-OPR) and 5-hydroxytryptamine receptor la (5HT1aR) are employed as model receptor targets. The key feature of this assay system is the isolation of stable, clonal Chinese hamster ovary (CHO) cell lines that carry three separate expression plasmids: (1) a chimeric Gq/i5 protein (which re-directs a negative Gi-type signal to a positive Gq-type response), (2) a given Gi-GPCR, and (3) a beta-lactamase (beta1a) reporter gene responsive to Gi-GPCR signaling. Cell-based assays built using this format show appropriate rank order of potency among a reference set of receptor agonist and antagonist compounds. Such assays are also robust, reliable, and can be used for industrial-scale applications such as high-throughput screening for drug leads.     

A thermostable phytase from Bacillus sp. MD2: cloning, expression and high-level production in Escherichia coli

Phytase is used as a feed additive for degradation of antinutritional phytate, and the enzyme is desired to be highly thermostable for it to withstand feed formulation conditions. A Bacillus sp. MD2 showing phytase activity was isolated, and the phytase encoding gene was cloned and expressed in Escherichia coli. The recombinant phytase exhibited high stability at temperatures up to 100°C. A higher enzyme activity was obtained when the gene expression was done in the presence of calcium chloride. Production of the enzyme by batch- and fed-batch cultivation in a bioreactor was studied. In batch cultivation, maintaining dissolved oxygen at 20–30% saturation and depleting inorganic phosphate below 1 mM prior to induction by IPTG resulted in over 10 U/ml phytase activity. For fed–batch cultivation, glucose concentration was maintained at 2–3 g/l, and the phytase expression was increased to 327 U/ml. Induction using lactose during fed-batch cultivation showed a lag phase of 4 h prior to an increase in the phytase activity to 71 U/ml during the same period as IPTG-induced production. Up to 90% of the total amount of expressed phytase leaked out from the E. coli cells in both IPTG- and lactose-induced fed-batch cultivations.     

Mechanism of shortened action potential duration in Na+-Ca2+ exchanger knockout mice

In cardiac-specific Na⁺-Ca²⁺ exchanger (NCX) knockout (KO) mice, the ventricular action potential (AP) is shortened. The shortening of the AP, as well as a decrease of the L-type Ca²⁺ current (I_Ca), provides a critical mechanism for the maintenance of Ca²⁺ homeostasis and contractility in the absence of NCX (Pott C, Philipson KD, Goldhaber JI. Excitation-contraction coupling in Na⁺-Ca²⁺ exchanger knockout mice: reduced transsarcolemmal Ca²⁺ flux. Circ Res 97: 1288–1295, 2005). To investigate the mechanism that underlies the accelerated AP repolarization, we recorded the transient outward current (I_to) in patch-clamped myocytes isolated from wild-type (WT) and NCX KO mice. Peak I_to was increased by 78% and decay kinetics were slowed in KO vs. WT. Consistent with increased I_to, ECGs from KO mice exhibited shortened QT intervals. Expression of the I_to-generating K⁺ channel subunit Kv4.2 and the K⁺ channel interacting protein was increased in KO. We used a computer model of the murine AP (Bondarenko VE, Szigeti GP, Bett GC, Kim SJ, and Rasmusson RL. Computer model of action potential of mouse ventricular myocytes. Am J Physiol Heart Circ Physiol 287: 1378–1403, 2004) to determine the relative contributions of increased I_to, reduced I_Ca, and reduced NCX current (I_NCX) on the shape and kinetics of the AP. Reduction of I_Ca and elimination of I_NCX had relatively small effects on the duration of the AP in the computer model. In contrast, AP repolarization was substantially accelerated when I_to was increased in the computer model. Thus, the increase in I_to, and not the reduction of I_Ca or I_NCX, is likely to be the major mechanism of AP shortening in KO myocytes. The upregulation of I_to may comprise an important regulatory mechanism to limit Ca²⁺ influx via a reduction of AP duration, thus preventing Ca²⁺ overload in situations of reduced myocyte Ca²⁺ extrusion capacity. genetically altered mice; cardiac myocytes; short QT interval; transient outward current