Purpose-To evaluate the effectiveness of mitigation of acute ionizing radiation damage by mitochondria-targeted small molecules.Materials and Methods-We evaluated the nitroxide-linked alkene peptide isostere JP4-039, the nitric oxide synthase inhibitor-linked alkene peptide esostere MCF201-89, and the p53/mdm2/ mdm4 inhibitor BEB55 in radiation mitigation by clonogenic survival curves with the murine hematopoietic progenitor cell line 32D cl 3, human bone marrow stromal (KM101) and pulmonary epithelial (IB3) cell line. The p53 dependent mechanism of action was tested with p53 +/+ and p53 −/− murine bone marrow stromal cell lines. C57BL/6 NHsd female mice were injected I.P. after 9.5 Gy total body irradiation (TBI) with JP4-039, MCF201-89, or BEB55 individually or in combination.Results-Each drug, JP4-039, MCF201-89, or BEB55, individually or as a mixture of all 3 compounds, increased the survival of 32D cl 3 cells and IB3 cells significantly over control irradiated cells (p=0.0021, p=0.0011, p=0.0038, and p=0.0073, respectively), and (p=0.0193, p=0.0452, p=0.0017, and p=0.0019 respectively). KM101 cells were protected by individual drugs (p=0.0007, p=0.0235, p=0.0044, respectively). JP4-039 and MCF201-89 increased irradiation survival of both p53+/+ (p=0.0396 and p=0.0071, respectively) and p53−/− cells (p=0.0007 and p=0.0188 respectively), while BEB55 was ineffective with (p53−/−) cells. Drugs administered individually or as a mixtures of all 3 after TBI significantly increased mouse survival (p=0.0234, 0.0009, 0.0052 and 0.0167 respectively).Corresponding Author: Joel S. Greenberger M.D., Department of Radiation Oncology, University of Pittsburgh Cancer Institute, 5150 Centre Avenue, Rm. 533, Pittsburgh, PA 15232, Tel: 412-647-3602, Fax: 412-647-1161, greenbergerjs@upmc

Mitochondria are key organelles that perform essential cellular functions and play pivotal roles in cell death and survival signaling. Hence, they represent an attractive target for drugs to treat metabolic, degenerative and hyperproliferative diseases. Targeting mitochondria with organellespecific agents or prodrugs has proven to be an effective therapeutic strategy. More specifically, controling the cellular ROS balance via selective delivery of an antioxidant "payload" into mitochondria is an elegant emerging therapeutic concept. Herein, we review the recent medicinal chemistry and clinical data of these exploratory strategies which should point the way for future generations of therapeutics.

Accumulation of senescent cells over time contributes to aging and age-related diseases. However, what drives senescence in vivo is not clear. Here we used a genetic approach to determine if spontaneous nuclear DNA damage is sufficient to initiate senescence in mammals. Ercc1-/∆ mice with reduced expression of ERCC1-XPF endonuclease have impaired capacity to repair the nuclear genome. Ercc1-/∆ mice accumulated spontaneous, oxidative DNA damage more rapidly than wild-type (WT) mice. As a consequence, senescent cells accumulated more rapidly in Ercc1-/∆ mice compared to repair-competent animals. However, the levels of DNA damage and senescent cells in Ercc1-/∆ mice never exceeded that observed in old WT mice. Surprisingly, levels of reactive oxygen species (ROS) were increased in tissues of Ercc1-/∆ mice to an extent identical to naturally-aged WT mice. Increased enzymatic production of ROS and decreased antioxidants contributed to the elevation in oxidative stress in both Ercc1-/∆ and aged WT mice. Chronic treatment of Ercc1-/∆ mice with the mitochondrial-targeted radical scavenger XJB-5–131 attenuated oxidative DNA damage, senescence and age-related pathology. Our findings indicate that nuclear genotoxic stress arises, at least in part, due to mitochondrial-derived ROS, and this spontaneous DNA damage is sufficient to drive increased levels of ROS, cellular senescence, and the consequent age-related physiological decline.

X-linked congenital nephrogenic diabetes insipidus (cNDI) results from inactivating mutations of the human arginine vasopressin (AVP) V2 receptor (hV 2 R). Most of these mutations lead to intracellular retention of the hV 2 R, preventing its interaction with AVP and thereby limiting water reabsorption and concentration of urine. Because the majority of cNDI-hV 2 Rs exhibit protein misfolding, molecular chaperones hold promise as therapeutic agents; therefore, we sought to identify pharmacochaperones for hV 2 R that also acted as agonists. Here, we describe high-affinity nonpeptide compounds that promoted maturation and membrane rescue of L44P, A294P, and R337X cNDI mutants and restored a functional AVP-dependent cAMP signal. Contrary to pharmacochaperone antagonists, these compounds directly activated a cAMP signal upon binding to several cNDI mutants. In addition, these molecules displayed original functionally selective properties (biased agonism) toward the hV 2 R, being unable to recruit arrestin, trigger receptor internalization, or stimulate mitogen-activated protein kinases. These characteristics make these hV 2 R agonist pharmacochaperones promising therapeutic candidates for cNDI. The antidiuretic hormone arginine-vasopressin (AVP) is crucial for osmoregulation, cardiovascular control, and water homeostasis. The human AVP V 2 receptor (hV 2 R), localized in the principal cells of the kidney collecting duct, mediates AVP antidiuretic effect and therefore helps in maintaining physiologic plasma osmolality, blood volume, and arterial pressure. Binding of AVP to hV 2 R first triggers a cAMP signal through activation of the G protein ␣ s (Gs) subunit and adenylyl cyclase (AC). Then, the cAMP-activated protein kinase A phosphorylates aquaporin 2 water channels, resulting in their insertion into the luminal membrane of principal cells and finally to water reabsorption. 1 AVP binding to hV 2 R also induces arrestin recruitment, receptor internalization, 2 and mitogen-activated protein kinase (MAPK) activation. 3 Mutations in the hV 2 R gene lead to the X-linked congenital nephrogenic diabetes insipidus (cNDI), a rare disease characterized by the kidney's inability to concentrate urine despite normal or elevated plasma concentrations of AVP. 4 More than 200 different mutations have been described and are responsible for polyuria, a main consequence of the disease. Most of the mutant receptors (cNDIhV 2 Rs), trapped in the endoplasmic reticulum

Very few nonpeptide oxytocin agonists have currently been reported, and none of them seem suitable for the in vivo investigation of the oxytocin mediated functions. In an attempt to rationalize the design of better tools, we have systematically studied the structural determinants of the affinity and efficacy of representative ligands of the V(1a), V(2), and OT receptor subtypes. Despite apparently obvious similarity between the ligand structures on one hand, and between the receptor subtypes on the other hand, the binding affinity and the functional activity profiles of truncated and hybrid ligands highlight the subtlety of ligand-receptor interactions for obtaining nonpeptide OT receptor agonists.

Fanconi anemia (FA) is an inherited disorder characterized by defective DNA repair and cellular sensitivity to DNA crosslinking agents. Clinically, FA is associated with high risk for marrow failure, leukemia and head and neck squamous cell carcinoma (HNSCC). Radiosensitivity in FA patients compromises the use of total-body irradiation for hematopoietic stem cell transplantation and radiation therapy for HNSCC. A radioprotector for the surrounding tissue would therefore be very valuable during radiotherapy for HNSCC. Clonogenic radiation survival curves were determined for pre- or postirradiation treatment with the parent nitroxide Tempol or JP4-039 in cells of four FA patient-derived cell lines and two transgene-corrected subclonal lines. FancG–/– (PD326) and FancD2–/– (PD20F) patient lines were more sensitive to the DNA crosslinking agent mitomycin C (MMC) than their transgene-restored subclonal cell lines (both P < 0.0001). FancD2–/– cells were more radiosensitive than the transgene restored subclonal cell line (ñ = 2.0 ± 0.7 and 4.7 ± 2.2, respectively, P = 0.03). In contrast, FancG–/– cells were radioresistant relative to the transgene-restored subclonal cell line (ñ = 9.4 ± 1.5 and 2.2 ± 05, respectively, P = 0.001). DNA strand breaks measured by the comet assay correlated with radiosensitivity. Cell lines from a Fanc-C and Fanc-A patients showed radiosensitivity similar to that of Fanc-D2–/– cells. A fluorophore-tagged JP4-039 (BODIPY-FL) analog targeted the mitochondria of the cell lines. Preirradiation or postirradiation treatment with JP4-039 at a lower concentration than Tempol significantly increased the radioresistance and stabilized the antioxidant stores of all cell lines. Tempol increased the toxicity of MMC in FancD2–/– cells. These data provide support for the potential clinical use of JP4-039 for normal tissue radioprotection during chemoradiotherapy in FA patients.

Protein kinase D (PKD) belongs to a family of serine/threonine kinases that play an important role in basic cellular processes and are implicated in the pathogenesis of several diseases. Progress in our understanding of the biological functions of PKD has been limited due to the lack of a PKD-specific inhibitor. The benzoxoloazepinolone CID755673 was recently reported as the first potent and kinase-selective inhibitor for this enzyme. For structure-activity analysis purposes, a series of analogs was prepared and their in vitro inhibitory potency evaluated.

Protein kinase D (PKD) is a member of a novel family of serine/threonine kinases that regulate fundamental cellular processes. PKD is implicated in the pathogenesis of several diseases, including cancer. Progress in understanding the biological functions and therapeutic potential of PKD has been hampered by the lack of specific inhibitors. The benzoxoloazepinolone CID755673 was recently identified as the first potent and selective PKD inhibitor. The study of structure-activity relationships (SAR) of this lead structure led to further improvements in PKD1 potency. We describe herein the synthesis and biological evaluation of novel benzothienothiazepinone analogs. We achieved a ten-fold increase in the in vitro PKD1 inhibitory potency for the second generation lead kb-NB142-70 and accomplished a transition to an almost equally potent novel pyrimidine scaffold, while maintaining excellent target selectivity. These promising results will guide the design of pharmacological tools to dissect PKD function and pave the way for the development of potential anti-cancer agents.