The tumor-specific targeting of chemotherapeutic agents for specific necrosis of cancer cells without affecting the normal cells poses a great challenge for researchers and scientists. Though extensive research has been carried out to investigate chemotherapy-based targeted drug delivery, the identification of the most promising strategy capable of bypassing non-specific cytotoxicity is still a major concern. Recent advancements in the arena of onco-targeted therapies have enabled safe and effective tumor-specific localization through stimuli-responsive drug delivery systems. Owing to their promising characteristic features, stimuli-responsive drug delivery platforms have revolutionized the chemotherapy-based treatments with added benefits of enhanced bioavailability and selective cytotoxicity of cancer cells compared to the conventional modalities. The insensitivity of stimuli-responsive drug delivery platforms when exposed to normal cells prevents the release of cytotoxic drugs into the normal cells and therefore alleviates the off-target events associated with chemotherapy. Contrastingly, they showed amplified sensitivity and triggered release of chemotherapeutic payload when internalized into the tumor microenvironment causing maximum cytotoxic responses and the induction of cancer cell necrosis. This review focuses on the physical stimuli-responsive drug delivery systems and chemical stimuli-responsive drug delivery systems for triggered cancer chemotherapy through active and/or passive targeting. Moreover, the review also provided a brief insight into the molecular dynamic simulations associated with stimuli-based tumor targeting.

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Treatment options for Alcohol Use Disorders (AUD) have minimally advanced since 2004, while the annual deaths and economic toll have increased alarmingly. Phosphodiesterase type 4 (PDE4) is associated with alcohol and nicotine dependence. PDE4 inhibitors were identified as a potential AUD treatment using a novel bioinformatics approach. We prioritized a newer PDE4 inhibitor, apremilast, as ideal for repurposing, (i.e. FDA approved for psoriasis, low incidence of adverse events, excellent safety profile), and tested it using multiple animal strains and models, as well as in a human Phase IIa study. We found that apremilast reduced binge-like alcohol intake and behavioral measures of alcohol motivation in mouse models of genetic risk for drinking to intoxication. Apremilast also reduced excessive alcohol drinking in models for stressfacilitated drinking and alcohol dependence. Using site-directed drug infusions and electrophysiology, we uncovered that apremilast may act to lessen drinking in mice by increasing neural activity in the nucleus accumbens, a key brain region in the regulation of alcohol intake. Importantly, apremilast (90 mg/d) reduced excessive drinking in non-treatment seeking individuals with AUD in a double blind, placebo-controlled study. These results demonstrate that apremilast suppresses excessive alcohol drinking across the spectrum of AUD severity.

A growing number of studies implicate alterations in glutamatergic signaling within the reward circuitry of the brain during alcohol abuse and dependence. A key integrator of glutamatergic signaling in the reward circuit is the nucleus accumbens, more specifically, the dopamine D1 receptor-expressing medium spiny neurons (D1-MSNs) within this region, which have been implicated in the formation of dependence to many drugs of abuse including alcohol. D1-MSNs receive glutamatergic input from several brain regions; however, it is not currently known how individual inputs onto D1-MSNs are altered by alcohol experience. Here, we investigate input-specific adaptations in glutamatergic transmission in response to varying levels of alcohol experience. Virally mediated expression of Channelrhodopsin in ventral hippocampal (vHipp) glutamate neurons of male mice allowed for selective activation of vHipp to D1-MSN synapses. Therefore, we were able to compare synaptic adaptations in response to low and high alcohol experience in vitro and in vivo. Alcohol experience enhanced glutamatergic activity and abolished LTD at vHipp to D1-MSN synapses. Following chronic alcohol experience, GluA2-lacking AMPARs, which are Ca permeable, were inserted into vHipp to D1-MSN synapses. These findings support the reversal of alcohol-induced insertion of Ca-permeable AMPARs and the enhancement of glutamatergic activity at vHipp to D1-MSNs as potential targets for intervention during early exposure to alcohol.Given the roles of the nucleus accumbens (NAc) in integrating cortical and allocortical information and in reward learning, it is vital to understand how inputs to this region are altered by drugs of abuse such as alcohol. The strength of excitatory inputs from the ventral hippocampus (vHipp) to the NAc has been positively associated with reward-related behaviors, but it is unclear whether or how ethanol affects these inputs. Here we show that vHipp-NAc synapses indeed are altered by ethanol exposure, with vHipp glutamatergic input to the NAc being enhanced following chronic ethanol experience. This work provides insight into ethanol-induced alterations of vHipp-NAc synapses and suggests that, similarly to drugs such as cocaine, the strengthening of these synapses promotes reward behavior.

Nucleus accumbens dopamine D1 receptor-expressing medium spiny neurons (D1-MSNs) have been implicated in the formation of dependence to many drugs of abuse including alcohol. Previous studies have revealed that acute alcohol exposure suppresses glutamatergic signaling within the accumbens and repeated alcohol exposure enhances glutamatergic signaling. D1-MSNs receive glutamatergic input from several brain regions and it is not currently known how individual inputs onto D1-MSNs are altered by alcohol experience. To Address this, we used virally mediated expression of Channelrhodopsin (ChR2) in ventral hippocampal (vHipp) glutamate neurons to selectively activate vHipp to D1-MSN synapses and compared synaptic adaptations in response to low and high alcohol experience in vitro and in vivo. Alcohol experience enhanced glutamatergic activity and abolished long-term depression (LTD) at ventral hippocampal (vHipp) to D1-MSN synapses. Following chronic alcohol experience GluA2lacking AMPA receptors, which are Ca-permeable, were inserted into vHipp to D1-MSN synapses. These alcohol-induced adaptations of glutamatergic signaling occurred at lower levels of exposure than previously reported. The loss of LTD expression and enhancement in glutamatergic signaling from the vHipp to D1-MSNs in the nucleus accumbens may play a critical role in the formation of alcohol dependence and enhancements in ethanol consumption. Reversal of alcohol-induced insertion of Ca-permeable AMPA receptors and enhancement of glutamatergic activity at vHipp to D1-MSNs presents potential targets for intervention during early exposure to alcohol. SIGNIFICANCE STATEMENTThe work presented here is the first to elucidate how an individual glutamatergic input onto D1-MSNs of the accumbens shell (shNAc) are altered by repeated ethanol exposure. Our findings suggest that glutamatergic input from the ventral hippocampus (vHipp) onto D1-MSNs is enhanced following drinking in a two-bottle choice (2BC) paradigm and is further enhanced by chronic intermittent ethanol (CIE) vapor exposure which escalated volitional ethanol intake.A critical finding was the insertion of Ca-permeable AMPA receptors into vHipp-shNAc D1-MSN synapses following CIE exposure, and more importantly following ethanol consumption in the absence of vapor exposure. These findings suggest that enhancements of glutamatergic input from the vHipp and insertion of Ca-permeable AMPARs play a role in the formation of ethanol dependence.