Highlights d Striosomes powerfully inhibit SNc dopamine neurons through GABA-BRs on SNr dendrite d Dopamine neurons show rebound activity after inhibition from the striatum, but not GPe d Striosomal inputs are synaptically optimized to produce rebound d Striosomes selectively inhibit ventral, rebound-ready dopamine neurons

Axons of dopaminergic neurons innervate the striatum where they contribute to movement and reinforcement learning. Past work has shown that striatal GABA tonically inhibits dopamine release, but whether GABA-A receptors directly modulate transmission or act indirectly through circuit elements is unresolved. Here, we use whole-cell and perforated-patch recordings to test for GABA-A receptors on the main dopaminergic neuron axons and branching processes within the striatum of adult mice. Application of GABA depolarized axons, but also decreased the amplitude of axonal spikes, limited propagation and reduced striatal dopamine release. The mechanism of inhibition involved sodium channel inactivation and shunting. Lastly, we show the positive allosteric modulator diazepam enhanced GABA-A currents on dopaminergic axons and directly inhibited release, but also likely acts by reducing excitation from cholinergic interneurons. Thus, we reveal the mechanisms of GABA-A receptor modulation of dopamine release and provide new insights into the actions of benzodiazepines within the striatum.

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Purpose: Vitamin E succinate (a-TOS) inhibits the growth of cancer cells without unacceptable side effects.Therefore, the mechanisms associated with the anticancer action of a-TOS, including ceramide-mediated apoptosis, were investigated using head and neck squamous cell carcinoma (HNSCC) in vitro and in vivo. Experimental Design: Five different human HNSCC cell lines (JHU-011, JHU-013, JHU-019, JHU-022, and JHU-029) were treated with a-TOS, and its effects on cell proliferation, cell cycle progression, ceramide-mediated apoptosis, and ceramide metabolism were evaluated. The anticancer effect of a-TOS was also examined on JHU-022 solid tumor xenograft growth in immunodeficient mice. Results: a-TOS inhibited the growth of all the HNSCC cell lines in vitro in a dose-and timedependent manner. Thus, JHU-013 and JHU-022 cell lines were more sensitive to a-TOS than the other cell lines. Cellular levels of ceramide, sphingomyelinase activity, caspase-3, and p53 were elevated with increasing time of exposure to a-TOS. The degradation of poly(ADP-ribose) polymerase protein in JHU-022 cells treated with a-TOS provided evidence for apoptosis. The amounts of nuclear factor nB, Bcl-2, and Bcl-X L proteins were reduced in the cells treated with a-TOS for 6 hours. The levels of caspase-9, murine double minute-2, and InB-a proteins were unchanged after a-TOS treatment. I.p. administration of a-TOS slowed tumor growth in immunodeficient mice. Conclusions: a-TOS showed promising anticancer effects to inhibit HNSCC growth and viability in vivo and in vitro. The induction of enzymes involved in ceramide metabolism by a-TOS suggests that ceramide-mediated apoptosis may expand therapeutic strategies in the treatment of carcinoma.Each year, f31,000 Americans are diagnosed with head and neck cancer and f7,400 die from the disease (1). Overall survival rates of head and neck cancers have only marginally improved over the last three decades (2). In addition, the incidence of oral cancer in African American men has been approximately twice higher than in Caucasian men, and the 5-year relative survival is lower for African Americans (1).Therefore, novel therapeutic and preventive approaches are warranted.Accumulating evidence suggested that an esterified derivative of RRR-a-tocopherol (a-TOH), RRR-a-tocopheryl succinate (a-TOS), is a vitamin E analogue, which inhibits tumor growth (3 -7). It induces apoptosis, inhibits tumor cell proliferation and differentiation, arrests DNA synthesis, and blocks cell cycle progression in various cancer cell lines and animal models of breast, colon, head and neck, prostate, and lung cancers (8 -18). In addition, a-TOS selectively kills tumor cells without toxic effects on normal cells and tissues (4,7,18). The parent compound of vitamin E, a-TOH, is a free radical -scavenging antioxidant, which protects polyunsaturated fats from peroxidation in human body but does not induce cancer cell apoptosis (19). In contrast to a-TOH, a-TOS is a redox-inactive molecule, which has a charged side group when i...

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The selective formation of nanomaterials in cancer cells and tumors holds great promise for cancer diagnostics and therapy. Until now, most strategies rely on a single trigger to control the formation of nanomaterials in situ. The combination of two or more triggers may provide for more sophisticated means of manipulation. In this study, we rationally designed a molecule (Comp. 1) capable of responding to two enzymes, alkaline phosphatase (ALP), and reductase. Since the A549 lung cancer cell line showed elevated levels of extracellular ALP and intracellular reductase, we demonstrated that Comp. 1 responded in a stepwise fashion to those two enzymes and displayed a tandem molecular self-assembly behavior. The selective formation of nanofibers in the mitochondria of the lung cancer cells led to the disruption of the mitochondrial membrane, resulting in an increased level of reactive oxygen species (ROS) and the release of cytochrome C (Cyt C). ROS can react with proteins, resulting in endoplasmic reticulum (ER) stress and the unfolded protein response (UPR). This severe ER stress led to disruption of the ER, formation of vacuoles, and ultimately, apoptosis of the A549 cells. Therefore, Comp. 1 could selectively inhibit lung cancer cells in vitro and A549 xenograft tumors in vivo. Our study provides a novel strategy for the selective formation of nanomaterials in lung cancer cells, which is powerful and promising for the diagnosis and treatment of lung cancer.

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Transferrin receptor (TfR) is overexpressed in human head and neck squamous cell carcinomas (HNSCCs). This study was carried out to investigate the feasibility of imaging HNSCC by targeting TfR using near-infrared fluorescent transferrin conjugate (TfNIR). Western blot analysis of four HNSCC cell lines revealed overexpression of TfR in all four lines compared with that in normal keratinocytes (OKFL). Immunocytochemistry further confirmed the expression of TfR and endocytosis of TfNIR in JHU-013 culture cells. Following intravenous administration of TfNIR (200 microL, 0.625 microg/microL), fluorescent signal was preferentially accumulated in JHU-013 tumor xenografts grown in the lower back (n=14) and oral base tissues (n=4) of nude mice. The signal in tumors was clearly detectable as early as 10 minutes and reached the maximum at 90 to 120 minutes postinjection. The background showed an increase, followed by a decrease at a much faster pace than tumor signal. A high fluorescent ratio of the tumor to muscle was obtained (from 1.42 to 4.15 among tumors), usually achieved within 6 hours, and correlated with the tumor size (r=.74, p=.002). Our results indicate that TfR is a promising target and that Tf(NIR)-based optical imaging is potentially useful for noninvasive detection of early HNSCC in the clinic.