Mechanistic insight of the role of NHERF1 in cisplatin-induced acute kidney injury.

Background. Acute kidney injury (AKI) develops in 30% of patients who receive cisplatin, a widely used chemotherapeutic agent. We previously showed that NHERF1 loss resulted in increased susceptibility to cisplatin nephrotoxicity. The overarching goal of this dissertation was to elucidate mechanisms of susceptibility to cisplatin-induced AKI, specifically the effects of NHERF1 loss on tubule cell metabolism, tubule cell mitochondrial function, and alterations in oxidative state and/or renal handling of cisplatin. Methods. 2-4 month male wild type (WT) and NHERF1 knock out (KO) mice were treated with either vehicle control or cisplatin (20 mg/kg dose IP) for 4, 24, and 72 hours. Urine was collected for NGAL and kidneys were harvested for histology and the following assays: Thiobarbituric Acid Reactive Substances (TBARS) for lipid peroxidation, γ-glutamyl transferase (GGT) activity, and Western Blot for GGT and cysteine S-conjugate beta lyase (CCBL). Mitochondrial respiration was conducted via the Seahorse XF24 analyzer on non-treated isolated kidney mitochondria. LC-MS analysis was used to evaluate ATP content in non-treated kidneys. Electron microscopy was utilized to evaluate mitochondrial morphology and number in non-treated kidneys. HPLC of the reduced and oxidized forms of the small molecular weight thiols (glutathione (GSH), glutathione disulfide (GSSG), cysteine (Cys), and cystine (CySS), and cysteine-glutathione disulfide (CySSG) on plasma and kidney cortex. Statistical analysis was completed using Student’s t-test for LC-MS, mitochondrial number, and mitochondrial respiration and Two-way ANOVA was used for all other analysis. P-values of Results. Chapter III demonstrates that WT and NHERF1 KO mice do not exhibit metabolic changes or changes in ATP content that would definitively sensitize the KO mice to cisplatin injury. Chapter IV shows that NHERF1 loss does not affect mitochondrial morphology or mitochondrial number, or oxidative phosphorylation capacity via Seahorse XF24 analysis. Thus, mitochondrial dysfunction does not appear to sensitize the KO mice to cisplatin injury. Lastly, Chapter V reveals that NHERF1 KO mouse kidneys do not exhibit changes in lipid peroxidation, oxidative stress, GGT or CCBL protein levels that would sensitize these animals to cisplatin. However, NHERF1 KO kidneys appear to respond differently to the cisplatin insult itself, characterized by differences in GGT activity in response to cisplatin. Conclusions. In conclusion, the work presented in this dissertation reveals that metabolic stress and mitochondrial dysfunction are not the mechanisms of susceptibility to cisplatin in NHERF1 KO mice. Furthermore, NHERF1 loss does not lead to changes in kidney GSH metabolism. In conclusion, these data do not support NHERF1 loss resulting in a fundamental metabolic defect that increases susceptibility to cisplatin injury. Instead NHERF1 loss appears to influence either the handling, the initial insult, or the response to injury resulting in exacerbated injury

Loss of the Na+/H+ exchange regulatory factor 1 results in increased susceptibility to cisplatin-induced acute kidney injury.

Background. Acute kidney injury (AKI), an abrupt loss of kidney function which carries a high mortality and confers an increased risk of chronic kidney disease, develops in 30% of patients who receive cisplatin, a widely used chemotherapeutic agent [1], [2], [3]. The sodium hydrogen exchange regulatory factor isoform 1 (NHERF1) is a scaffolding protein that anchors multiple membrane proteins, in renal proximal tubules [4]. NHERF-1 deficient mice have aberrant localization of BBM proteins in intracellular compartments [5]. The investigators have recently demonstrated NHERF1 deficient proximal tubule cells have an underlying increase in PERK phosphorylation and that NHERF1 deficiency results in altered mitochondrial protein expression and function. Since mitochondria and endoplasmic reticulum (ER) are physically and functionally connected, the purpose of this study was to test the hypothesis that NHERF1 loss increases susceptibility to AKI through an underlying ER stress. Methods. Male and female WT C57BL/6J and NHERF1 KO mice were treated with vehicle or cisplatin (20 mg/kg dose IP) and euthanized after 72 hours. Blood was collected for blood urea nitrogen (BUN) levels. Kidneys were harvested for histology (hematoxylin and eosin; periodic acid schiff), TUNEL assay, RT-qPCR of Kidney Injury Molecule-1 (KIM-1), and Western Blot for cleaved caspase 3, p-eIF2α, p58IPK, GRP94 and GRP78. Results. Cisplatin caused significantly greater severity of injury in NHERF1 KO mice compared to WT mice as demonstrated by semi-quantitative injury score and BUN levels (p=0.023). KIM-1 mRNA expression was significantly increased in both WT and NHERF1 KO cisplatin treated mice (p=0.0153) in comparison to vehicle treated mice. TUNEL assay analysis showed significant increases in both NHERF1 KO and WT cisplatin treated mice (pIPK(p=0.20) expression was decreased with cisplatin treatment in WT and NHERF1 KO mice and not different between vehicle treated WT and NHERF1 KO mice. A significant increase in GRP94 expression was seen (p=0.030) in cisplatin treated NHERF1 KO mice compared to cisplatin treated WT mice. Thus, there were no significant gender differences found between WT and NHERF1 KO mice for any of the measured parameters, except for eIF2α phosphorylation and cleavage of caspase 3. Conclusions. These data suggest that an underlying ER stress is not the mechanism of susceptibility in NHERF1 KO mice. In conclusion, this study provides a novel role for NHERF1 and susceptibility to cisplatin-induced AKI

Intra-industry trade in Latin America and the Caribbean

An increasingly important component of total world trade is intra-industry trade (IIT). The large volume of literature on IIT is reflective of this importance. However, this extensive literature has focused almost completely on explaining the causes of IIT. This focus has left a puzzling gap in the literature. Specifically, it is almost impossible to determine the level of IIT for a particular country or region. Further, there is almost no information on the level of IIT at the industry level either globally or for a region or country. In this paper we provide estimates of IIT for the world and for the countries of the Western Hemisphere. Further, we provide estimates of IIT for ten different SITC product categories on the same basis. The findings of the paper indicate that in most industries, IIT in Latin America is substantially lower overall than the world average. There are, however, substantial variations observed both by country and by industry. Because the results are the first available for the region as a whole, they should allow researchers to get a better picture of the extent of IIT in Latin America and the Caribbean by country and by industry.Intra-industry trade; Latin America

Functional form for United States-México trade equations

The literature concerning bilateral trade flows between Mexico and the United States is comparatively small. With the growing importance of international commerce between these economies, potential trade flow responses to changes in relative prices and income performance deserves more attention. This paper attempts to partially fill this gap in the literature by estimating bilateral trade flow equations that decompose relative import and relative export prices into foreign prices, domestic prices, and the exchange rate.

Tuning the electron-phonon coupling in multilayer graphene with magnetic fields

Magneto Raman scattering study of the E$_{2g}$ optical phonons in multi-layer epitaxial graphene grown on a carbon face of SiC are presented. At 4.2K in magnetic field up to 33 T, we observe a series of well pronounced avoided crossings each time the optically active inter Landau level transition is tuned in resonance with the E$_{2g}$ phonon excitation (at 196 meV). The width of the phonon Raman scattering response also shows pronounced variations and is enhanced in conditions of resonance. The experimental results are well reproduced by a model that gives directly the strength of the electron-phonon interaction.Comment: 4 pages, 3 figure

Resonant Excitation of Graphene K-Phonon and Intra-Landau-Level Excitons in Magneto-Optical Spectroscopy

Precise infrared magnetotransmission experiments have been performed in magnetic fields up to 32 T on a series of multilayer epitaxial graphene samples. We observe changes in the spectral features and broadening of the main cyclotron transition when the incoming photon energy is in resonance with the lowest Landau level separation and the energy of a K point optical phonon. We have developed a theory that explains and quantitatively reproduces the frequency and magnetic field dependence of the phenomenon as the absorption of a photon together with the simultaneous creation of an intervalley, intra-Landau-level exciton, and a K phonon.Comment: Main manuscript (5 pages); Supplementary Material (18 pages

Magneto-transmission of multi-layer epitaxial graphene and bulk graphite: A comparison

Magneto-transmission of a thin layer of bulk graphite is compared with spectra taken on multilayer epitaxial graphene prepared by thermal decomposition of a SiC crystal. We focus on the spectral features evolving as \sqrt{B}, which are evidence for the presence of Dirac fermions in both materials. Whereas the results on multi-layer epitaxial graphene can be interpreted within the model of 2D Dirac fermions, the data obtained on bulk graphite can only be explained taking into account the 3D nature of graphite, e.g. by using the standard Slonczewski-Weiss-McClure model.Comment: 5 pages, 2 figure

Effect of a magnetic field on the two-phonon Raman scattering in graphene

We have studied, both experimentally and theoretically, the change of the so-called 2D band of the Raman scattering spectrum of graphene (the two-phonon peak near 2700 cm-1) in an external magnetic field applied perpendicular to the graphene crystal plane at liquid helium temperature. A shift to lower frequency and broadening of this band is observed as the magnetic field is increased from 0 to 33 T. At fields up to 5--10 T the changes are quadratic in the field while they become linear at higher magnetic fields. This effect is explained by the curving of the quasiclassical trajectories of the photo-excited electrons and holes in the magnetic field, which enables us (i) to extract the electron inelastic scattering rate, and (ii) to conclude that electronic scattering accounts for about half of the measured width of the 2D peak.Comment: 11 pages, 7 figure

Bilayer graphene inclusions in rotational-stacked multilayer epitaxial graphene

Additional component in multi-layer epitaxial graphene grown on the C-terminated surface of SiC, which exhibits the characteristic electronic properties of a AB-stacked graphene bilayer, is identified in magneto-optical response of this material. We show that these inclusions represent a well-defined platform for accurate magneto-spectroscopy of unperturbed graphene bilayers.Comment: 5 pages, 2 figures, to appear in Phys. Rev.