How does active yeast supplementation reduce the deleterious effects of aflatoxins in Wistar rats? A radiolabeled assay and histopathological study

The aim of this study was to investigate the mechanisms by which yeasts (Saccharomyces cerevisiae) control the toxic effects of aflatoxins, which are not yet fully understood. Radiolabeled aflatoxin B1 (AFB13H) was administered by gavage to Wistar rats fed with aflatoxin (AflDiet) and aflatoxin supplemented with active dehydrated yeast Y904 (AflDiet + Yeast). The distribution of AFB13H and its metabolites were analyzed at 24, 48 and 72 h by tracking back of the radioactivity. No significant differences were observed between the AflDiet and AflDiet + Yeast groups in terms of the distribution of labeled aflatoxin. At 72 h, for the AflDiet group the radiolabeled aflatoxin was distributed as following: feces (79.5%), carcass (10.5%), urine (1.7%), and intestine (7.4%); in the AflDiet + Yeast the following distribution was observed: feces (76%), carcass (15%), urine (2.9%), and intestine (4.9%). These values were below 1% in other organs. These findings indicate that even after 72 h considerable amounts of aflatoxins remains in the intestines, which may play a significant role in the distribution and metabolism of aflatoxins and its metabolites over time. The presence of yeast may not significantly affect this process. Furthermore, histopathological examination of hepatic tissues showed that the presence of active yeast reduced the severity of liver damage caused by aflatoxins, indicating that yeasts control aflatoxin damage through biochemical mechanisms. These findings contribute to a better understanding of the mechanisms underlying the protective effects of yeasts against aflatoxin toxicity.

Homodimer 99mTc-HYNIC-E(SSSLTVPWY)2 peptide improved HER2-overexpressed tumor targeting and imaging

We hypothesized that a novel design of the LTVPWY (LY) peptide might exhibit a great potential for improving binding affinity and targeting HER2-overexpressed tumors. Hence, new dimer construction of ^99mTc-labeled LY [^99mTc-HYNIC-E(SSSLTVPWY)₂] (^99mTc-DLY) was introduced. Afterward, a head-to-head comparison of in vitro and in vivo experiments was performed between ^99mTc-DLY and ^99mTc-HYNIC-SSSLTVPWY as the monomer analog. The blocking dosage of trastuzumab reduced the uptake of the dimer about 20% more efficiently than the monomer in the SKOV-3 cell line. A twofold increase in competitive binding affinity and biological half-life was observed for ^99mTc-DLY. The ovarian-tumor-bearing mice were detected with high contrast where the tumor-to-muscle ratio of ^99mTc-DLY was notably increased about 40% using a gamma camera. The biodistribution experiment revealed an approximately 10% enhancement in tumor/blood, tumor/muscle, and tumor/bone ratios for the dimer. More rapid blood clearance was another achievement of the homodimer design. Overall, ^99mTc-DLY successfully affected the pharmacokinetics and consequently the visualization of HER2-overexpressing tumors.

The Radiolabeled HER3 Targeting Molecules for Tumor Imaging

The human epidermal growth factor receptor (HER) family plays pivotal roles in physiologic and pathologic conditions (such as tumor growth, proliferation, and progression in multiple epithelial malignancies). All the family members are considered tyrosine kinase, while HER3 as a member of this family shows no intrinsic tyrosine kinase. HER3 is called ‘pseudokinase’ because it undergoes heterodimerization and forms dimers such as HER2-HER3 and HER1 (EGFR)-HER3. The exact role of HER3 in cancer is still unclear; however, the overexpression of this receptor is involved in the poor prognosis of malignancies. To that end, different studies investigated the development of radiotracers for imaging of HER3. The main focus of this review is to gather all the studies on developing new radiotracers for imaging of HER3.

Targeting and imaging of HER2 overexpression tumor with a new peptide-based 68Ga-PET radiotracer

Human epidermal growth factor receptor 2 (HER2) overexpression, as a predictive biomarker, is associated with more tumor aggressiveness and worse clinical outcomes in cancer, whereas it's accurate identification has led to the choice of effective treatments in many patients. In this study, a peptide-based PET probe (⁶⁸Ga-DOTA-(Ser)₃-LTVSPWY) was developed for imaging HER2 expression in tumors. The DOTA-(Ser)₃-LTVSPWY was labeled with ⁶⁸Ga and then was evaluated in vitro with HER2-positive SKOV-3 cell line; moreover, the in vivo biodistribution and PET/CT imaging were performed in xenografted tumor-bearing nude mice. The ⁶⁸Ga-DOTA-(Ser)₃-LTVSPWY displayed the high radiochemical purity greater than 95% and good stability in normal saline and human serum. The cellular binding experiments showed that the cell uptake in HER2-positive ovarian cancer cells could be effectively blocked by non-labeled peptide. The K_d and B_max values for radiolabeled peptide were obtained at 2.5 ± 0.6 nM and (3.4 ± 0.2) × 10⁵ sites per cell, respectively. Biodistribution study demonstrated that tumor-to-blood and tumor-to-muscle ratios were about 1.73 ± 0.36 and 3.78 ± 0.17 at 120 min after the injection of the radiolabeled peptide, respectively. Tumor imaging by PET/CT exhibited high contrast tumor image at 60 min after injection in animal models. Consequently, the results were indicative of the specific accumulation of ⁶⁸Ga-DOTA-(Ser)₃-LTVSPWY peptide in HER2-positive tumors and the suitability of its application as a PET probe for the diagnosis of HER2-overexpression tumor.

An Investigation of the Usability of Solid Lipid Nanoparticles Radiolabelled with Tc-99m as Imaging Agents in Liver-Spleen Scintigraphy

In this work, solid lipid nanoparticles (SLNs) were prepared by microemulsion and ultrasonication methods in the first stage of the production process of 99mTc–SLNs, which is considered to be an alternative radiopharmaceutical for the liver-spleen scintigraphy within the nuclear medicine. The laser diffraction (LD) and X-ray diffraction (XRD) analysis showed that these particles were at nano scale and had β' polymorph structure, respectively. It was observed that there was no interaction between the solid lipid and the surfactant molecules by fourier transform infrared spectroscopy (FT-IR). The scanning electron microscope (SEM) and transmission electron microscopy (TEM) images were taken and seen that the SLNs were spherical and at nano scale. Thermogravimetric analysis (TGA) for stability confirmed that they were stable for temperature variations. In the second stage of the study, the SLNs were successfully labeled with 99mTc. The radiolabeling efficiency was found to be greater than %95 and in vivo studies were performed on experimental rabbits using scintigraphic methods. When the obtained images were examined, the uptake was observed in the heart, the lungs, the liver, and the spleen. It was concluded that SLNs labeled with 99mTc could be a selective imaging agent. It was asserted to be a new radiopharmaceutical, especially as an alternative to the 99mTc-labeled compounds used in the liver and spleen imaging in colloid scintigraphy.

Absorption, metabolism, and excretion of [14C]ponatinib after a single oral dose in humans

Purpose

Ponatinib is a novel tyrosine kinase inhibitor (TKI) specifically designed to inhibit native and mutated BCR–ABL. In the United States, ponatinib has received accelerated approval for adults with T315I-positive chronic myeloid leukemia (CML) or T315I (gatekeeper mutation)-positive, Philadelphia chromosome-positive, acute lymphoblastic leukemia (Ph + ALL), and patients with CML or Ph + ALL for whom no other TKI therapy is indicated. The objective of this phase 1, mass balance study was to evaluate the absorption, metabolism, and excretion of [¹⁴C]ponatinib in healthy subjects.

Methods

A single 45-mg [¹⁴C]ponatinib dose was administered orally to six healthy male volunteers, and absorption, metabolism, and excretion were assessed.

Results

86.6 and 5.4% of the dose was recovered in feces and urine, respectively, during days 0–14 postdose. Median time to maximal plasma radioactivity was 5 h and mean terminal elimination half-life of radioactivity was 66.4 h. Ponatinib and its inactive carboxylic acid metabolite M14, the two major circulating radioactive components, accounted for 25.5 and 14.9% of the radioactivity in 0–24 h pooled plasma, with elimination half-lives of 27.4 and 33.7 h, respectively. Major metabolites in urine were M14 and its glucuronides, which, together with other M14-derived metabolites, represented 4.4% of the dose; ponatinib was not detected in urine. In feces, major radioactive components were ponatinib, M31 (hydroxylation), M42 (N-demethylation), and four methylated products accounting for 20.5, 17.7, 8.3, and 8.4% of the radioactive dose, respectively.

Conclusions

Ponatinib was readily absorbed in humans, metabolized through multiple pathways and was eliminated mostly in feces.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-017-3240-x) contains supplementary material, which is available to authorized users.

Tissue uptake, distribution and elimination of (14)C-PFOA in zebrafish (Danio rerio)

Perfluorooctanoic acid (PFOA) is a long-chain perfluorinated chemical that has been shown to be non-degradable and persistent in the environment. Laboratory studies on bioconcentration and compound-specific tissue distribution in fish can be valuable for prediction of the persistence and environmental effects of the chemicals. In the present study male and female zebrafish (Danio rerio) were continuously exposed to 10μg/L of radiolabeled perfluorooctanoic acid ((14)C-PFOA) for 40 days, after which the exposed fish were transferred to fresh clean water for another 80 days wash-out period. At defined periodic intervals during the uptake and wash-out, fish were sampled for liquid scintillation counting and whole body autoradiography to profile the bioconcentration and tissue distribution of PFOA. The steady-state concentration of (14)C-PFOA in the zebrafish was reached within 20-30 days of exposure. The concentration-time course of (14)C-PFOA displayed a bi-exponential decline during washout, with a terminal half-life of approximately 13-14 days. At steady-state the bioconcentration of (14)C-PFOA into whole-body fish was approximately 20-30 times greater than that of the exposure concentration, with no differences between females and males. The bioconcentration factors for liver and intestine were approximately 100-fold of the exposure medium, while in brain, ovary and gall bladder the accumulation factors were in the range 15-20. Whole-body autoradiograms confirmed the highest labeling of PFOA in bile and intestines, which implies enterohepatic circulation of PFOA. The (14)C-PFOA was also observed in maturing vitellogenic oocytes, suggesting chemical accumulation via yolk proteins into oocytes with plausible risk for adverse effects on early embryonic development and offspring health. The bioconcentration at several (14)C-PFOA exposure concentrations were also investigated (0.3-30μg/L). This showed that bioconcentration increased linearly with tank exposure in the present in vivo model under steady-state conditions. From this model tissue concentrations of PFOA can be predicted when the external exposure level is known. The present study has generated experimental data on PFOA kinetics in zebrafish that can be valuable for aquatic environmental risk assessment.

Radiolabeled NGR phage display peptide sequence for tumor targeting

The asparagine-glycine-arginine (NGR) peptide sequence found by phage display, was radiolabeled with technetium-99m and tested in different tumor models. Similar uptake occurred with ovarian and lung tumor cells. Biodistribution of the radiotracer revealed predominant renal excretion with more substantial uptake in animals bearing ovarian tumor cells. In contrast imaging studies indicated better visualization for lung tumor. NGR peptide was characterized as a promising diagnostic candidate, particularly for lung cancer. Improvements are envisaged using NGR combined with RGD as a heterodimer molecule.