Substantia nigra (SNc) dopaminergic neurons respond to aversive stimuli with inhibitory pauses in firing followed by transient rebound activation. We tested integration of inhibitory synaptic inputs ...onto SNc neurons from genetically defined populations in dorsal striatum (striosome and matrix) and external globus pallidus (GPe; parvalbumin- and Lhx6-positive), and examined their contribution to pause-rebound firing. Activation of striosome projections, which target “dendron bouquets” in the pars reticulata (SNr), consistently quiets firing and relief from striosome inhibition triggers rebound activity. Striosomal inhibitory postsynaptic currents (IPSCs) display a prominent GABA-B receptor-mediated component that strengthens the impact of SNr dendrite synapses on somatic excitability and enables rebounding. By contrast, GPe projections activate GABA-A receptors on the soma and proximal dendrites but do not result in rebounding. Lastly, optical mapping shows that dorsal striatum selectively inhibits the ventral population of SNc neurons, which are intrinsically capable of rebounding. Therefore, we define a distinct striatonigral circuit for generating dopamine rebound.
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•Striosomes powerfully inhibit SNc dopamine neurons through GABA-BRs on SNr dendrite•Dopamine neurons show rebound activity after inhibition from the striatum, but not GPe•Striosomal inputs are synaptically optimized to produce rebound•Striosomes selectively inhibit ventral, rebound-ready dopamine neurons
Evans et al. functionally map inhibitory inputs onto SNc dopamine neuron dendrites from genetically defined basal ganglia subpopulations. Using two-photon calcium imaging and computational modeling, they reveal a dendrite-specific striatonigral circuit that facilitates dopamine neuron rebound activity.
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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Intravitreal/periocular injection of triamcinolone acetonide (TA) suspension is a common uveitis treatment, but it displays a high risk for serious side effects (e.g., high ...intraocular pressure, retinal toxicity). We report here an intravitreally injectable thermosensitive glycosylated TA (TA-SA-Glu) hydrogel, formed by covalently conjugating glucosamine (Glu) with succinate TA (TA-SA), for treating uveitis. The TA-SA-Glu hydrogelator forms a supramolecular hydrogel spontaneously in aqueous solution with a minimal gelation concentration of 0.25 wt%. Structural analysis revealed that hydrogen bonds assisted by hydrophobic interaction resulted in self-assembled nanofibers. Rheology analysis demonstrated that this TA-SA-Glu hydrogel exhibited a typical thixotropic property. Sustained release of both TA-SA-Glu and TA from the hydrogel occurred throughout the 3-day in vitro release study. The obtained TA-SA-Glu hardly caused cytotoxicity against ARPE-19 and RAW264.7 cells after 24 h of incubation at drug concentration up to 600 μM. In particular, TA-SA-Glu exhibited a comparable anti-inflammatory efficacy to TA in terms of inhibiting the production of nitric oxide, tumor necrosis factor-α, and interleukin-6 in activated RAW264.7 macrophages. Following a single intravitreal injection, 69 nmol TA-SA-Glu hydrogel caused minimal apparent retinal toxicity, whereas the TA suspension displayed significant effects in terms of localized retinal toxicity. A single intravitreal injection of TA-SA-Glu hydrogel was more effective in controlling inflammatory response than that of the TA suspension treatment, particularly in down-regulating the pro-inflammatory Th1 and Th17 effector responses for treating experimental autoimmune uveitis. This study strongly indicates that supramolecular TA-SA-Glu hydrogels may represent a new option for posterior uveitis management.
Intravitreal/periocular injection of triamcinolone acetonide (TA) suspension is a common uveitis treatment, but suffers a high risk for serious side effects (e.g., high intraocular pressure, retinal toxicity). We generated an injectable glycosylated triamcinolone acetonide hydrogelator (TA-SA-Glu) hydrogel for treating uveitis. Following a single intravitreal injection, the proposed TA-SA-Glu hydrogel hardly caused apparent retinal toxicity at a dosage of 69 nmol per eye. Furthermore, TA-SA-Glu hydrogel was more effective in controlling non-infectious uveitis over than a TA suspension, particularly in terms of down-regulating the pro-inflammatory Th1 and Th17 effector responses for treating experimental autoimmune uveitis (EAU). This study strongly indicates that TA-SA-Glu supramolecular hydrogels may represent a new option for the management of various intraocular inflammations.
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
. The combination of two or more triggers may provide for more sophisticated means of manipulation. In this study, we rationally designed a molecule (
) 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
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,
could selectively inhibit lung cancer cells
and A549 xenograft tumors
. 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.
Vitamin E succinate (alpha-TOS) inhibits the growth of cancer cells without unacceptable side effects. Therefore, the mechanisms associated with the anticancer action of alpha-TOS, including ...ceramide-mediated apoptosis, were investigated using head and neck squamous cell carcinoma (HNSCC) in vitro and in vivo.
Five different human HNSCC cell lines (JHU-011, JHU-013, JHU-019, JHU-022, and JHU-029) were treated with alpha-TOS, and its effects on cell proliferation, cell cycle progression, ceramide-mediated apoptosis, and ceramide metabolism were evaluated. The anticancer effect of alpha-TOS was also examined on JHU-022 solid tumor xenograft growth in immunodeficient mice.
Alpha-TOS inhibited the growth of all the HNSCC cell lines in vitro in a dose- and time-dependent manner. Thus, JHU-013 and JHU-022 cell lines were more sensitive to alpha-TOS than the other cell lines. Cellular levels of ceramide, sphingomyelinase activity, caspase-3, and p53 were elevated with increasing time of exposure to alpha-TOS. The degradation of poly(ADP-ribose) polymerase protein in JHU-022 cells treated with alpha-TOS provided evidence for apoptosis. The amounts of nuclear factor kappaB, Bcl-2, and Bcl-X(L) proteins were reduced in the cells treated with alpha-TOS for 6 hours. The levels of caspase-9, murine double minute-2, and IkappaB-alpha proteins were unchanged after alpha-TOS treatment. I.p. administration of alpha-TOS slowed tumor growth in immunodeficient mice.
Alpha-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 alpha-TOS suggests that ceramide-mediated apoptosis may expand therapeutic strategies in the treatment of carcinoma.
The growth of prostate tumors is mediated by the bioavailability of androgens and insulin-like growth factors. This study tested the hypothesis that healthy young adult African American men ...exhibiting low aerobic capacity (fitness) have serum insulin-like growth Factor-1 (IGF-1) and testosterone levels that promote growth of prostate cancer cells. A cross-sectional data research design was used to study groups of 18- to 26-year-old healthy men exhibiting low and moderate aerobic fitness, based on their peak oxygen consumption (VO2peak). The individual serum levels of IGF-1, IGF-1 binding protein-3 (IGFBP-3), and testosterone were measured. In vitro growth of androgen-dependent LNCaP prostate tumor cells was measured after incubation in culture medium fortified with each subject’s serum. Aerobic capacity was significantly greater in the moderate-fitness group than in the low-fitness group without an intergroup difference in body mass index. The serum IGF-1 concentration was significantly higher in the low-fitness group in the absence of an intergroup difference in serum testosterone. The serum IGFBP-3 concentration was significantly lower in the low-fitness group. Prostate tumor cell growth was significantly greater in the cultures incubated in media containing the sera of the low-fitness group than in the sera of the moderate-fitness group. These findings suggest that moderate aerobic fitness in young adults may decrease the circulating levels of free IGF-1 and lower the potential to support growth of prostate cancer cells.
Subcellular delivery of nanomedicines has emerged as a promising approach to enhance the therapeutic efficacy of anticancer drugs. Nuclear accumulation of anticancer drugs are essential for its ...therapeutic efficacy because their targets are generally located within the nucleus. However, strategies for the nuclear accumulation of nanomedicines with anticancer drugs rarely reported. In this study, we reported a promising nanomedicine, comprising a drug-peptide amphiphile, with enhanced cellular uptake and nuclear accumulation capability for cancer therapy. The drug-peptide amphiphile consisted of the peptide ligand PMI (TSFAEYWNLLSP), which was capable of activating the p53 gene by binding with the MDM2 and MDMX located in the cell nucleus. Peptide conformations could be finely tuned by using different strategies including heating-cooling and enzyme-instructed self-assembly (EISA) to trigger molecular self-assembly at different temperatures. Due to the different peptide conformations, the drug-peptide amphiphile self-assembled into nanomedicines with various properties, including stabilities, cellular uptake, and nuclear accumulation. The optimized nanomedicine formed by EISA strategy at a low temperature of 4 °C showed enhanced cellular uptake and nuclear accumulation capability, and thus exhibited superior anticancer ability both in vitro and in vivo. Overall, our study provides a useful strategy for finely tuning the properties and activities of peptide-based supramolecular nanomaterials, which may lead to optimized nanomedicines with enhanced performance.
Subcellular delivery of nanomedicines was a promising approach to enhance the therapeutic efficacy of anticancer drugs. Nuclear accumulation of anticancer drugs are essential for its therapeutic efficacy because their targets are generally located within the nucleus. In this study, we reported a promising drug-peptide amphiphile, including peptide ligand PMI and anticancer drug HCPT. Different path of assembly led to different properties, including conformation, stability cellular uptake and nuclear accumulation. The resulting nanomedicine formed by EISA s 4 °C showed enhanced cellular uptake and nuclear accumulation capability, and thus exhibited superior anticancer ability both in vitro and in vivo. Overall, our study provides a useful strategy for finely tuning the properties and activities of peptide-based supramolecular nanomaterials, which may lead to optimized nanomedicines with enhanced performance. Display omitted
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•A prodrug supramolecular hydrogel was prepared using a pH hydrolytic strategy.•The supramolecular hydrogel displayed long-term stability over 30 day after lyophilization.•The ...supramolecular hydrogel significantly extend the precorneal retention.
The low bioavailability exhibits by conventional ocular formulation owing to rapid precorneal clearance and lower corneal permeability can be overcame by the application of the gelling system. In the present study, a prodrug supramolecular hydrogel derived from succinated dexamethasone (Dex-SA) was fabricated using a pH hydrolytic strategy and explored as a “self-delivery” system for ophthalmic drugs. The self-assembled Dex-SA supramolecular hydrogel exhibited a typical nano-fibrous microstructure and was thixotropic. Both dexamethasone (Dex) and Dex-SA prodrug sustainably released from Dex-SA supramolecular hydrogel in a period of 120 h in vitro release study, and the initial pH value of hydrogel significantly influence on the release ratio of Dex/Dex-SA. Furthermore, the lyophilized Dex-SA supramolecular hydrogel displayed long-term stability without causing any apparent hydrolysis of Dex-SA at −20 °C over 30 day and quickly re-formed a hydrogel after dissolving into aqueous solution. The formed Dex-SA supramolecular hydrogel had lower cytotoxicity than Dex at drug concentration up to 2.5 mM, and exhibited a comparable anti-inflammatory efficacy to a Dex sodium phosphate (Dexp) aqueous solution in lipopolysaccharide-activated RAW264.7 macrophages. Topical instillation of the Dex-SA supramolecular hydrogel showed excellent intraocular biocompatibility and it was not an irritant in rabbit eyes. More importantly, the Dex-SA supramolecular hydrogel provided a prolonged precorneal retention and significantly enhanced the ocular bioavailability over Dexp aqueous solution after topical instillation. Overall, this work illustrates an effective approach for the development of prodrug supramolecular hydrogels to extend the precorneal retention and enhance ocular bioavailability of drugs after topical instillation.
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Noninfectious (autoimmune and immune-mediated) uveitis is an ocular inflammatory disease which can lead to blindness in severe cases. Due to the potential side effects of first-line ...drugs for clinical uveitis, novel drugs and targets against uveitis are still urgently needed. In the present study, using rat experimental autoimmune uveitis (EAU) model, we first found that minocycline treatment can substantially inhibit the development of EAU and improve the retinal function by suppressing the retinal microglial activation, and block the infiltration of inflammatory cells, including Th17, into the retina by decreasing the major histocompatibility complex class II (MHC II) expression in resident and infiltrating cells. Moreover, we demonstrated that minocycline treatment can remodel the gut microenvironment of EAU rats by restoring the relative abundance of Ruminococcus bromii, Streptococcus hyointestinalis, and Desulfovibrio sp. ABHU2SB and promoting a functional shift in the gut via reversing the levels of L-proline, allicin, aceturic acid, xanthine, and leukotriene B4, and especially increasing the production of propionic acid, histamine, and pantothenic acid. At last, we revealed that minocycline treatment can significantly attenuate the progression of EAU after inflammation onset, which may be explained by the role of minocycline in the remodeling of the gut microenvironment since selective elimination of retinal microglia on the later stages of EAU was shown to have little effect. These data clearly demonstrated that inhibition of microglial activation and remodeling of the gut microenvironment can suppress the development and progression of experimental autoimmune uveitis. Considering the excellent safety profile of minocycline in multiple clinical experiments, we suggest that minocycline may have therapeutic implications for clinical uveitis.
•A drug-peptide prodrug hydrogel was rationally designed and screened.•The prodrug hydrogel formed spontaneously in phosphate buffered saline.•The prodrug hydrogel did not induce the apparent ocular ...side-effects.•The prodrug hydrogel effectively alleviate the experimental autoimmune uveitis.
Glucocorticoids (e.g., dexamethasone (Dex)) are the mainstay in the treatment of non-infectious uveitis, but optimal drug delivery system to maximally realize its potent bioactivity is still lacking. In the present study, we rationally designed and screened a dexamethasone-peptide amphiphile (Dex-GGD), which instantly formed a prodrug supramolecular hydrogel in phosphate-buffered saline (PBS, pH = 7.4) without external stimuli for the topical ocular drug delivery. The obtained Dex-GGD hydrogel was thoroughly characterized by rheology, circular dichroism (CD), and transmission electron microscopy (TEM). The results showed that Dex-GGD exhibited a potent in vitro anti-inflammatory capacity in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages with minimal cytotoxicity against L-929 fibroblasts, ARPE-19 cells, and RAW 264.7 macrophages. In a rat model of experimental autoimmune uveitis (EAU), the severity of uveitis was significantly alleviated after the treatment with Dex-GGD hydrogel owing to its potent ability to reduce the influx of inflammatory cells from peripheral blood and suppress the activation of macroglia and microglia in the retina. In contrast to the treatment with an equivalent dose of dexamethasone sodium phosphate (Dexp), the intravitreal injection of Dex-GGD hydrogel hardly induced the apparent ocular side-effects (e.g., elevated intraocular pressure or fundus blood vessel tortuosity). As a result, the proposed Dex-GGD prodrug supramolecular hydrogel may be an effective and safe therapeutic option for improving the clinical management of uveitis.
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