Egg-derived tri-peptide IRW exerts antihypertensive effects in spontaneously hypertensive rats

Background

There is a growing interest in using functional food components as therapy for cardiovascular diseases such as hypertension. We have previously characterized a tri-peptide IRW (Ile-Arg-Trp) from egg white protein ovotransferrin; this peptide showed anti-inflammatory, anti-oxidant and angiotensin converting enzyme (ACE) inhibitor properties invitro. Given the pathogenic roles played by angiotensin, oxidative stress and inflammation in the spontaneously hypertensive rat (SHR), we tested the therapeutic potential of IRW in this well-established model of hypertension.

Methods and Results

16–17 week old male SHRs were orally administered IRW at either a low dose (3 mg/Kg BW) or a high dose (15 mg/Kg BW) daily for 18 days. Blood pressure (BP) and heart rate were measured by telemetry. Animals were sacrificed at the end of the treatment for vascular function studies and measuring markers of inflammation. IRW treatment attenuated mean BP by ~10 mmHg and ~40 mmHg at the low- and high-dose groups respectively compared to untreated SHRs. Heart rate was not affected. Reduction in BP was accompanied by the restoration of diurnal variations in BP, preservation of nitric oxide dependent vasorelaxation, as well as reduction of plasma angiotensin II, other inflammatory markers and tissue fibrosis.

Conclusion

Our results demonstrate anti-hypertensive effects of IRW invivo likely mediated through ACE inhibition, endothelial nitric oxide synthase and anti-inflammatory properties.

Successful isolated intestinal transplantation in sensitized recipients with the use of virtual crossmatching

We evaluated virtual crossmatching (VXM) for organ allocation and immunologic risk reduction in sensitized isolated intestinal transplantation recipients. All isolated intestine transplants performed at our institution from 2008 to 2011 were included in this study. Allograft allocation in sensitized recipients was based on the results of a VXM, in which the donor-specific antibody (DSA) was prospectively evaluated with the use of single-antigen assays. A total of 42 isolated intestine transplants (13 pediatric and 29 adult) were performed during this time period, with a median follow-up of 20 months (6-40 months). A sensitized (PRA ≥ 20%) group (n = 15) was compared to a control (PRA < 20%) group (n = 27) to evaluate the efficacy of VXM. With the use of VXM, 80% (12/15) of the sensitized patients were transplanted with a negative or weakly positive flow-cytometry crossmatch and 86.7% (13/15) with zero or only low-titer (≤ 1:16) DSA. Outcomes were comparable between sensitized and control recipients, including 1-year freedom from rejection (53.3% and 66.7% respectively, p = 0.367), 1-year patient survival (73.3% and 88.9% respectively, p = 0.197) and 1-year graft survival (66.7% and 85.2% respectively, p = 0.167). In conclusion, a VXM strategy to optimize organ allocation enables sensitized patients to successfully undergo isolated intestinal transplantation with acceptable short-term outcomes.

The emergence of resistance to amikacin in Serratia marcescens isolates from patients with nosocomial infection

Administration of either amikacin (1985) or gentamicin (1984, 1986-1991) as first-choice aminoglycoside did not decrease the high incidence of amikacin-resistant Serratia marcescens (ARSm) isolates responsible for nosocomial infections at the J.A. Fernández Hospital of Buenos Aires (42% in 1984, 31% in 1985 and 41% in 1987, differences not significant). In addition, a significant peak (P = 0.003) was detected in 1986, with an ARSm incidence of 70%. The incidence of ARSm decreased by 1988-1991 for reasons not related to aminoglycoside use. In the period 1984-1987 all S. marcescens isolates carried the 6'-aminoglycoside-acetyltransferase-Ic [aac(6')-Ic] gene, while in addition 20% of the isolates contained the plasmid-encoded 3'-aminoglycoside-phosphotransferase-VIa[aph(3')-VIa] and 2% the 6'-aminoglycoside-acetyltransferase-Ib [aac(6')-Ib] genes. From 1988 to 1992 resistance to amikacin was associated with only 4 ARSm isolates and correlated with the appearance of Tn1331-related sequences in these isolates. This transposon or related sequences, however, was not widely spread in the S. marcescens population under investigation. Combined use of restriction fragment length polymorphism (RFLP), ribotyping and plasmid profile analysis revealed that S. marcescens strains of the same genotype, including isolates either expressing or not the aac(6')-Ic gene, were involved in outbreaks occurring in May 1984, May 1985 and May 1986. Furthermore, these epidemiological tools permitted discrimination of different S. marcescens clones, each bearing a particular amikacin-resistance marker.

Angiotensin-converting enzyme 2 antagonizes angiotensin II-induced pressor response and NADPH oxidase activation in Wistar-Kyoto rats and spontaneously hypertensive rats

Angiotensin-converting enzyme 2 (ACE2), a monocarboxypeptidase capable of metabolizing angiotensin II (Ang II) into angiotensin-(1-7) [Ang-(1-7)], has emerged as a potential therapeutic target. We hypothesized that ACE2 is a negative regulator of Ang II-mediated pathological effects in vivo. In Wistar-Kyoto (WKY) rats, Ang II infusion (0.1 μg min(-1) kg(-1)) induced a pressor response, activation of NADPH oxidase and generation of superoxide in the heart, kidney and blood vessels; these effects were significantly blunted by recombinant human ACE2 (rhACE2; 2 mg kg(-1)), in association with a lowering of plasma Ang II and elevation of Ang-(1-7) levels. In the spontaneously hypertensive rat (SHR) model, rhACE2 (2 mg kg(-1) day(-1)) delivered over a 14 day period partly corrected the hypertension, the NADPH oxidase activation and the increased superoxide generation in the heart, kidney and blood vessels. Treatment with rhACE2 inhibited Ang II-mediated phosphorylation of the myocardial extracellular signal-regulated kinase 1/2 pathway in WKY rats, with congruent results seen in SHR hearts. Hence, rhACE2 is an important negative regulator of the Ang II-induced pressor response and NADPH oxidase activation and suppresses pathological myocardial signalling, thereby providing a novel therapeutic agent with which to antagonize an activated renin-angiotesin system.

Abnormal CX3CR1⁺ lamina propria myeloid cells from intestinal transplant recipients with NOD2 mutations

Although progress has been made in intestinal transplantation, chronic inflammation remains a challenge. We have reported that the risk of immunological graft loss is almost 100-fold greater in recipients who carry any of the prevalent NOD2 polymorphisms associated with Crohn's disease, and have shown that the normal levels of a key antimicrobial peptide produced by the Paneth cells of the allograft, fall as the graft becomes repopulated by hematopoietic cells of the NOD2 mutant recipient. These studies are extended in this report. Within several months following engraftment into a NOD2 mutant recipient the allograft loses its capacity to prevent adherence of lumenal microbes. Despite the significantly increased expression of CX3CL1, a stress protein produced by the injured enterocyte, NOD2 mutant CX3CR1(+) myeloid cells within the lamina propria fail to exhibit the characteristic morphological phenotype, and fail to express key genes required expressed by NOD2 wild-type cells, including Wnt 5a. We propose that the CX3CR1(+) myeloid cell within the lamina propria supports normal Paneth cell function through expression of Wnt 5a, and that this function is impaired in the setting of intestinal transplantation into a NOD2 mutant recipient. The therapeutic value of Wnt 5a administration in this setting is proposed.

Anti-tumor activity of motesanib in a medullary thyroid cancer model

BACKGROUND

Medullary thyroid cancer (MTC) is frequently associated with mutations in the tyrosine kinase Ret and with increased expression of vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2). Motesanib is an investigational, orally administered small molecule antagonist of VEGFR1, 2, and 3; platelet-derived growth factor receptor (PDGFR); Kit; and possibly Ret.

AIM

The aim of this study was to investigate the effects of motesanib on wildtype and mutant Ret activity in vitro and on tumor xenograft growth in a mouse model of MTC.

METHODS/RESULTS

In cellular phosphorylation assays, motesanib inhibited the activity of wild-type Ret (IC(50)=66 nM), while it had limited activity against mutant Ret C634W (IC(50)=1100 nM) or Ret M918T (IC(50)>2500 nM). In vivo, motesanib significantly inhibited the growth of TT tumor cell xenografts (expressing Ret C634W) and significantly reduced tumor blood vessel area and tumor cell proliferation, compared with control. Treatment with motesanib resulted in substantial inhibition of Ret tyrosine phosphorylation in TT xenografts and, at comparable doses, in equivalent inhibition of VEGFR2 phosphorylation in both TT xenografts and in mouse lung tissue.

CONCLUSIONS

The results of this study demonstrate that motesanib inhibited thyroid tumor xenograft growth predominantly through inhibition of angiogenesis and possibly via a direct inhibition of VEGFR2 and Ret expressed on tumor cells. These data suggest that targeting angiogenesis pathways and specifically the VEGF pathway may represent a novel therapeutic approach in the treatment of MTC.

Identification of NVP-BKM120 as a Potent, Selective, Orally Bioavailable Class I PI3 Kinase Inhibitor for Treating Cancer

Phosphoinositide-3-kinases (PI3Ks) are important oncology targets due to the deregulation of this signaling pathway in a wide variety of human cancers. Herein we describe the structure guided optimization of a series of 2-morpholino, 4-substituted, 6-heterocyclic pyrimidines where the pharmacokinetic properties were improved by modulating the electronics of the 6-position heterocycle, and the overall druglike properties were fine-tuned further by modification of the 4-position substituent. The resulting 2,4-bismorpholino 6-heterocyclic pyrimidines are potent class I PI3K inhibitors showing mechanism modulation in PI3K dependent cell lines and in vivo efficacy in tumor xenograft models with PI3K pathway deregulation (A2780 ovarian and U87MG glioma). These efforts culminated in the discovery of 15 (NVP-BKM120), currently in Phase II clinical trials for the treatment of cancer.

Six-month incidence of bloodstream infections in intestinal transplant patients

BACKGROUND

Intestinal transplantation has emerged as an established treatment for life-threatening intestinal failure. The most common complication and cause of death is infection. Risk of infection is highest during the first 6 months, as a consequence of maximal immunosuppression, greater than that required for any other organ allograft.

METHODS

We performed a retrospective chart review of all (56) adult and pediatric (<18 years) small bowel transplant patients at our institution between November 2003 and July 2007, and analyzed the 6-month post-transplant incidence of bloodstream infections (BSIs). We evaluated multiple risk factors, including inclusion of a colon or liver, total bilirubin >5, surgical complications, and acute rejection.

RESULTS

A BSI developed in 34 of the 56 patients, with a total of 85 BSI episodes. Of these BSI episodes, 65.9% were due to gram-positive organisms, 34.1% gram-negative organisms, and 2.4% due to fungi. The most common isolates were Enterococcus species, Enterobacter species, Klebsiella species, and coagulase-negative staphylococci. Inclusion of the liver and/or a preoperative bilirubin >5 mg/dL appeared to increase the incidence of BSI (P = 0.0483 and 0.0005, respectively). Acute rejection and colonic inclusion did not appear to affect the incidence of BSI (P = 0.9419 and 0.8248, respectively). The BSI incidence was higher in children (P = 0.0058).

CONCLUSIONS

BSIs are a common complication of intestinal transplantation. Risk factors include age <18, inclusion of the liver, and pre-transplant bilirubin >5. Acute rejection and colon inclusion do not appear to be associated with increased BSI risk.

Structural resemblances and comparisons of the relative pharmacological properties of imatinib and nilotinib

Although orphan drug applications required by the EMEA must include assessments of similarity to pre-existing products, these can be difficult to quantify. Here we illustrate a paradigm in comparing nilotinib to the prototype kinase inhibitor imatinib, and equate the degree of structural similarity to differences in properties. Nilotinib was discovered following re-engineering of imatinib, employing structural biology and medicinal chemistry strategies to optimise cellular potency and selectivity towards BCR-ABL1. Through evolving only to conserve these properties, this resulted in significant structural differences between nilotinib and imatinib, quantified by a Daylight-fingerprint-Tanimoto similarity coefficient of 0.6, with the meaning of this absolute measure being supported by an analysis of similarity distributions of similar drug-like molecules. This dissimilarity is reflected in the drugs having substantially different preclinical pharmacology and a lack of cross-intolerance in CML patients, which translates into nilotinib being an efficacious treatment for CML, with a favourable side-effect profile.

Constriction of rat extra-splenic veins to lipopolysaccharide involves endothelin-1

The spleen has an important role in blood volume regulation and increased resistance of post-capillary hilar veins (in mesentery adjoining the spleen) can regulate this. This study investigated whether venular constriction to lipopolysaccharide (LPS) involved endothelin-1 (ET-1). Pressure myography was used to study isolated extra-splenic (hilar) vessels from male Wistar rats (n = 111). Arteries and veins were treated with LPS (50 microg ml(-1)) for 4 h. Extra-splenic veins constricted to LPS (p < 0.05), but there was no effect on arteries. Denudation did not abolish venular constriction to LPS, indicating an endothelial independent mechanism. However, the dual ET-1 receptor antagonist bosentan (10(-5) M) and specific ET(A) and ET(B) antagonists ABT-627 (atrasentan, 6.3 x 10(-6) M) and A-192621(1.45 x 10(-6) M) completely abolished constriction of LPS-treated veins. ET-1 alone also constricted the extra-splenic arteries and veins (p < 0.05), with a greater response observed in veins (p < 0.05). ELISA also confirmed that serum and spleen levels of ET-1 increased in response to LPS (p < 0.05). That LPS-induced constriction of extra-splenic veins is mediated by ET-1. Greater constriction of post- versus pre-capillary extra-splenic vessels to LPS would result in increased intra-splenic fluid extravasation and hypovolaemia in vivo.

Abstract 3629: BLZ945, a selective c-fms (CSF-1R) kinase inhibitor for the suppression of tumor-induced osteolytic lesions in bone

Aberrant activation of osteoclasts due to bone metastasis causes osteolysis, skeletal-related events and severe pain in cancer patients. Macrophage-Colony-stimulating Factor (M-CSF) signaling through its receptor c-fms / Colony-Stimulating Factor-1 Receptor (CSF-1R) in the monocytic lineage is essential for osteoclastogenesis, providing an opportunity to inhibit this pathway and suppress tumor-induced osteolysis. BLZ945 is an orally active, potent and selective CSF-1R inhibitor. BLZ945 inhibits CSF-1R activity with an IC50 of 1nM and is more than 1000-fold selective against its closest receptor tyrosine kinase homologs c-KIT and Platelet-derived Growth Factor Receptor beta (PDGFRb) as well as more than 200 additional kinases, confirming the selectivity of the compound. BLZ945 potently inhibited proliferation of the M-CSF-dependent murine leukemia cell line MNFS60 (EC50 67 nM) consistent with the inhibition of the CSF-1R kinase activity. Tyrosine phosphorylation in HEK293 cells overexpressing human CSF-1R was inhibited with an EC50 of 58 nM. Functional activity of BLZ945 was shown by inhibition of osteoclastogenesis using human osteoclast precursors.

The MNFS60 allograft model was used to evaluate the pharmacodynamics of BLZ945 by monitoring dose and time dependent changes in tyrosine phoshorylation of CSF-1R to select doses and regimens for in vivo efficacy studies. A single dose of BLZ945 at 200 mg/kg maximally suppressed CSF-1R phosphorylation of &gt;50% for more than 16 hours in this model and was selected for further evaluation in mouse models of breast (MDA-MB-231Luc) and prostate (PC-3MLuc) tumor-induced osteolysis (TIO). In these models human tumor cells are injected directly into the tibia of nude mice and bone destruction is measured by x-ray analysis and serum levels of tartrate-resistant acid phosphatase 5b (TRAP5b), a marker of osteoclast activity. Daily dosing of BLZ945 at 200 mg/kg resulted in a significant reduction in the progression of osteolysis, with &gt; 50% reduction in osteolytic lesion severity in both TIO models, as compared to vehicle-treated animals. Reductions in serum TRAP5b were also observed at the end of the studies. BLZ945 showed enhanced activity in combination with zoledronate in the PC-3MLuc model, with the combination reducing osteolytic severity scores by 90%. In addition anti-osteolytic activity was observed in a nude rat model of osteolysis induced by intratibial injection of MDA-MB-231 cells. In naïve cynomolgus monkeys, treatment with BLZ945 resulted in dose-dependent reductions of serum TRAP5b and cross-linked collagen (CTX) in both serum and urine, consistent with the expected effect of inhibiting bone resorption. These data support the testing of CSF-1R inhibitors in advanced cancer patients with bone metastases and skeletal related events.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3629.

Abstract 20: Raf kinase inhibitors can induce Raf dimerization, downstream signaling, and cell growth

Genetic alterations in the Ras/Raf/MEK/ERK pathway are among the most common in human cancers. Up to 70% of melanomas harbor B-Raf mutations, and roughly 90% of pancreatic tumors have K-Ras mutations. To address these Raf pathway-driven cancers, small molecule Raf kinase inhibitors have been developed and are currently under clinical investigation. In B-RafV600E cells, Raf compounds inhibit signaling through MEK and ERK, resulting in the expected anti-proliferative effects. Paradoxically, in wild-type Raf cells and in mutant Ras cells, these compounds induce downstream signaling and can induce cell growth in some settings in vitro. While the induction of downstream signaling has previously been attributed to published Raf pathway feedback loops, this has not been proven directly. In fact, we show here that induction of pMEK and pERK can occur within minutes of Raf compound treatment, even before reported feedback phosphorylation events are seen on B-Raf and C-Raf. Interestingly, the induction of signaling and cell growth both occur in a biphasic pattern, with low compound concentrations (0.01-0.1 uM) causing maximal induction, and higher compound concentrations (1-10 uM) causing less profound induction. Such a biphasic pattern is also observed in biochemical assays with purified wild-type B-Raf or C-Raf. The biphasic pattern is suggestive of a mechanism involving the interaction of two signaling subunits. In addition, recent literature data (Rajakulendran, Nature, 461:542-6) has demonstrated that Raf dimerization can upregulate pMEK, not through trans-phosphorylation of Raf molecules but presumably by conformational activation of the kinase. Consistent with that model, we show that Raf compound treatment induces B/C-Raf dimer formation in cells. In addition, knockdown of A-, B- or C-Raf with siRNA does not abrogate the Raf compound induction of pMEK and pERK, suggesting that induction might be mediated by Raf homo- as well as hetero-dimerization. Notably, knockdown of K-Ras in K-RasMUT cells also does not abolish the induction, implying that this effect is not mediated by Ras. Taken together, these data suggest a model in which compound binding to one Raf molecule induces dimerization and conformational activation of a partner Raf molecule in the dimer. These observations can explain why wild-type Raf and mutant Ras tumors are insensitive to selective Raf kinase inhibitors and might also have important implications for toxicity, since induction of strong mitogenic signaling could lead to hyperproliferation of normal tissues. Understanding the Raf compound induction mechanism may lead not only to the design of improved inhibitors, but also to methods for overcoming the induction seen with current development compounds. Toward that end, we show that combining a MEK inhibitor with a Raf compound causes inhibition of both pERK and cell growth and may therefore have significant advantages in the clinic.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 20.

Role of spleen in integrated control of splanchnic vascular tone: physiology and pathophysiology

Aside from its established immunologic and hematologic functions, the spleen also plays an important role in cardiovascular regulation. This occurs through changes in intrasplenic microvascular tone, as well as through splenic neurohormonal modulation of the renal and mesenteric vascular beds. Splenic regulation of blood volume occurs predominantly through fluid extravasation from the splenic circulation into lymphatic reservoirs; this is controlled by direct modulation of splenic pre- and postcapillary resistance by established physiologic agents such as atrial natriuretic peptide (ANP), nitric oxide (NO), and adrenomedullin (ADM). In addition to physiologic fluid regulation, splenic extravasation is a key factor in the inability to maintain adequate intravascular volume in septic shock. The spleen also controls renal microvascular tone through reflex activation of the splenic afferent and renal sympathetic nerves. This splenorenal reflex not only contributes to the physiologic regulation of blood pressure, but also contributes to the cardiovascular dysregulation associated with both septic shock and portal hypertension. In septic shock, the splenorenal reflex protectively limits splenic extravasation and potentially promotes renal sodium and water reabsorption and release of the vasoconstrictor angiotensin II; this function is eventually overwhelmed as shock progresses. In portal hypertension, on the other hand, the splenorenal reflex-mediated reduction in renal vascular conductance exacerbates sodium and water retention in the kidneys and may eventually contribute to renal dysfunction. Preliminary evidence suggests that the spleen also may play a role in the hemodynamic complications of portal hypertension via neurohormonal modulation of the mesenteric vascular bed. Lastly, the spleen itself may be a source of a vasoactive factor.