Effects of natural products on cisplatin ototoxicity and chemotherapeutic efficacy

INTRODUCTION

Cisplatin is a very effective chemotherapeutic agent against a variety of solid tumors. Unfortunately, cisplatin causes permanent sensorineural hearing loss in at least two-thirds of patients treated. There are no FDA approved drugs to prevent this serious side effect.

AREAS COVERED

This paper reviews various natural products that ameliorate cisplatin ototoxicity. These compounds are strong antioxidants and anti-inflammatory agents. This review includes mostly preclinical studies but also discusses a few small clinical trials with natural products to minimize hearing loss from cisplatin chemotherapy in patients. The interactions of natural products with cisplatin in tumor-bearing animal models are highlighted. A number of natural products did not interfere with cisplatin anti-tumor efficacy and some agents actually potentiated cisplatin anti-tumor activity.

EXPERT OPINION

There are a number of natural products or their derivatives that show excellent protection against cisplatin ototoxicity in preclinical studies. There is a need to insure uniform standards for purity of drugs derived from natural sources and to ensure adequate pharmacokinetics and safety of these products. Natural products that protect against cisplatin ototoxicity and augment cisplatin's anti-tumor effects in multiple studies of tumor-bearing animals are most promising for advancement to clinical trials. The most promising natural products include honokiol, sulforaphane, and thymoquinone.

Abstract 2564: Targeting IGF-1/STAT3 signaling crosstalk to inhibit prostate cancer growth and metastasis

Introduction: Prostate cancer is the most prevalent cancer in American men with unknown etiology. Signal transducer and activator of transcription 3 (STAT3) is a transcription factor, which has been implicated in the growth and metastasis of prostate cancer. Activation of STAT3 through phosphorylation modulates the expression of miR-21, an oncomir, by directly binding to their promoter region in response to various cytokines and growth factors. One such growth factor is insulin-like growth factor (IGF)-1, whose elevated levels are linked to the growth of prostate cancer. IGF-1 exerts its mitogenic effect by binding to its receptor, IGF-1R, whose expression on prostate cancer cells is also increased during neoplastic transformation. There is limited information concerning the crosstalk between IGF-1/IGF-1R and STAT3 signaling pathways which could explain their oncogenic roles in prostate cancer. In this study, we examined whether STAT3-mediated increase of miR-21 is critical for the proliferative effects of IGF-1. We further show that resveratrol, a polyphenolic antioxidant, attenuates prostate cancer growth and invasiveness through regulation of IGF-1/STAT3 pathway.

Methods: In vitro studies were performed on DU145 cells, which are androgen receptor negative human prostate cancer cells. Cell viability was assessed by MTS assays, while invasion and migration of cells were tested by Boyden chamber assay and wound healing assay, respectively. Modulation of protein expression was determined by Western blotting. MiR-21 levels were determined by TaqMan assay. SiRNA transfections were performed to suppress the expression of specific proteins in order to elucidate the molecular mechanisms underlying the actions of IGF-1, STAT3 and resveratrol.

Results: Acute IGF-1 treatment of DU145 cells increased phosphorylation of Akt which was correlated with the activation of STAT3. This effect of IGF-1 was through activation of IGF-1R, as siRNA-mediated knockdown of IGF-1R attenuated STAT3 activation and Akt phosphorylation. IGF-1 treatment also increased miR-21 levels and decreased the expression of its downstream protein, programmed cell death 4 (PDCD4). Effects of IGF-1 were completely attenuated by resveratrol. Furthermore, knockdown of IGF-1R and STAT3 mimicked the actions of resveratrol on DU145 cells suggesting that a signaling crosstalk exists between IGF-1 and STAT3 pathways which can be targeted to inhibit prostate cancer.

Conclusion: This study demonstrates, for the first time, that IGF-1 treatment significantly activates STAT3 pathway and increases miR-21 expression in prostate cancer cells. Targeted inhibition of IGF-1-induced activation of STAT3 by resveratrol holds the promise for the development of novel therapeutic agents against prostate cancer.

Citation Format: Sandeep Sheth, Raheem Al-Aameri, Vickram Ramkumar. Targeting IGF-1/STAT3 signaling crosstalk to inhibit prostate cancer growth and metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2564.

Targeting CXCL1 chemokine signaling for treating cisplatin ototoxicity

Cisplatin is chemotherapy used for solid tumor treatment like lung, bladder, head and neck, ovarian and testicular cancers. However, cisplatin-induced ototoxicity limits the utility of this agent in cancer patients, especially when dose escalations are needed. Ototoxicity is associated with cochlear cell death through DNA damage, the generation of reactive oxygen species (ROS) and the consequent activation of caspase, glutamate excitotoxicity, inflammation, apoptosis and/or necrosis. Previous studies have demonstrated a role of CXC chemokines in cisplatin ototoxicity. In this study, we investigated the role of CXCL1, a cytokine which increased in the serum and cochlea by 24 h following cisplatin administration. Adult male Wistar rats treated with cisplatin demonstrated significant hearing loss, assessed by auditory brainstem responses (ABRs), hair cell loss and loss of ribbon synapse. Immunohistochemical studies evaluated the levels of CXCL1 along with increased presence of CD68 and CD45-positive immune cells in cochlea. Increases in CXCL1 was time-dependent in the spiral ganglion neurons and organ of Corti and was associated with progressive increases in CD45, CD68 and IBA1-positive immune cells. Trans-tympanic administration of SB225002, a chemical inhibitor of CXCR2 (receptor target for CXCL1) reduced immune cell migration, protected against cisplatin-induced hearing loss and preserved hair cell integrity. We show that SB225002 reduced the expression of CXCL1, NOX3, iNOS, TNF-α, IL-6 and COX-2. Similarly, knockdown of CXCR2 by trans-tympanic administration of CXCR2 siRNA protected against hearing loss and loss of outer hair cells and reduced ribbon synapses. In addition, SB225002 reduced the expression of inflammatory mediators induced by cisplatin. These results implicate the CXCL1 chemokine as an early player in cisplatin ototoxicity, possibly by initiating the immune cascade, and indicate that CXCR2 is a relevant target for treating cisplatin ototoxicity.

Synthesis, crystal structure and in silico studies of novel 2,4-dimethoxy-tetrahydropyrimido[4,5-b]quinolin-6(7H)-ones

Herein, acetic acid mediated multicomponent synthesis of novel 2,4-dimethoxy-tetrahydropyrimido[4,5-b]quinolin-6(7H)-one (2,4-dimethoxy-THPQs) was reported. Single-crystal XRD analysis of four newly developed crystals of 2,4-dimethoxy-THPQs and their DFT study were also reported. The structure of all molecules was optimized using DFT B3LYP/6-31G(d) level and compared with the corresponding single-crystal XRD data. As a result, the theoretical and experimental geometrical parameters (bond lengths and bond angles) were found to be in good agreement. Frontier molecular orbital (FMO) and molecule electrostatic potential (MEP) analyses were used to investigate the physicochemical properties and relative reactivity of 2,4-dimethoxy-THPQs. The formation of strong C–H⋯O and N–H⋯O interaction was investigated by Hirshfeld analysis. Furthermore, electronic charge density concentration in 2,4-dimethoxy-THPQs was analysed by the Mulliken atomic charges which helps to predict the ability of 2,4-dimethoxy-THPQs to bind in the receptor. The molecular docking of the crystal structure of 2,4-dimethoxy-THPQs in the main protease (M^pro) of SARS-CoV-2 suggested that all four 2,4-dimethoxy-THPQs efficiently docked in M^pro. Furthermore, 2,4-dimethoxy-THPQs with a 3-chloro substitution in the phenyl ring have the highest binding affinity because of the additional formation of halogen bonds and highest dipole moment.

Single-crystal XRD analysis of 2,4-dimethoxy THPQs and their relative reactivity with properties were investigated using DFT calculation. Molecular docking studies show they effectively docked with main protease of SARS-CoV-2.

Transient Receptor Potential Channels and Auditory Functions

Significance: Transient receptor potential (TRP) channels are cation-gated channels that serve as detectors of various sensory modalities, such as pain, heat, cold, and taste. These channels are expressed in the inner ear, suggesting that they could also contribute to the perception of sound. This review provides more details on the different types of TRP channels that have been identified in the cochlea to date, focusing on their cochlear distribution, regulation, and potential contributions to auditory functions. Recent Advances: To date, the effect of TRP channels on normal cochlear physiology in mammals is still unclear. These channels contribute, to a limited extent, to normal cochlear physiology such as the hair cell mechanoelectrical transduction channel and strial functions. More detailed information on a number of these channels in the cochlea awaits future studies. Several laboratories focusing on TRPV1 channels have shown that they are responsive to cochlear stressors, such as ototoxic drugs and noise, and regulate cytoprotective and/or cell death pathways. TRPV1 expression in the cochlea is under control of oxidative stress (produced primarily by NOX3 NADPH oxidase) as well as STAT1 and STAT3 transcription factors, which differentially modulate inflammatory and apoptotic signals in the cochlea. Inhibition of oxidative stress or inflammation reduces the expression of TRPV1 channels and protects against cochlear damage and hearing loss. Critical Issues: TRPV1 channels are activated by both capsaicin and cisplatin, which produce differential effects on the inner ear. How these differential actions are produced is yet to be determined. It is clear that TRPV1 is an essential component of cisplatin ototoxicity as knockdown of these channels protects against hearing loss. In contrast, activation of TRPV1 by capsaicin protected against subsequent hearing loss induced by cisplatin. The cellular targets that are influenced by these two drugs to account for their differential profiles need to be fully elucidated. Furthermore, the potential involvement of different TRP channels present in the cochlea in regulating cisplatin ototoxicity needs to be determined. Future Directions: TRPV1 has been shown to mediate the entry of aminoglycosides into the hair cells. Thus, novel otoprotective strategies could involve designing drugs to inhibit entry of aminoglycosides and possibly other ototoxins into cochlear hair cells. TRP channels, including TRPV1, are expressed on circulating and resident immune cells. These receptors modulate immune cell functions. However, whether they are activated by cochlear stressors to initiate cochlear inflammation and ototoxicity needs to be determined. A better understanding of the function and regulation of these TRP channels in the cochlea could enable development of novel treatments for treating hearing loss. Antioxid. Redox Signal. 36, 1158-1170.

Oxidative Stress and Inflammation Caused by Cisplatin Ototoxicity

Hearing loss is a significant health problem that can result from a variety of exogenous insults that generate oxidative stress and inflammation. This can produce cellular damage and impairment of hearing. Radiation damage, ageing, damage produced by cochlear implantation, acoustic trauma and ototoxic drug exposure can all generate reactive oxygen species in the inner ear with loss of sensory cells and hearing loss. Cisplatin ototoxicity is one of the major causes of hearing loss in children and adults. This review will address cisplatin ototoxicity. It includes discussion of the mechanisms associated with cisplatin-induced hearing loss including uptake pathways for cisplatin entry, oxidative stress due to overpowering antioxidant defense mechanisms, and the recently described toxic pathways that are activated by cisplatin, including necroptosis and ferroptosis. The cochlea contains G-protein coupled receptors that can be activated to provide protection. These include adenosine A1 receptors, cannabinoid 2 receptors (CB2) and the Sphingosine 1-Phosphate Receptor 2 (S1PR2). A variety of heat shock proteins (HSPs) can be up-regulated in the cochlea. The use of exosomes offers a novel method of delivery of HSPs to provide protection. A reversible MET channel blocker that can be administered orally may block cisplatin uptake into the cochlear cells. Several protective agents in preclinical studies have been shown to not interfere with cisplatin efficacy. Statins have shown efficacy in reducing cisplatin ototoxicity without compromising patient response to treatment. Additional clinical trials could provide exciting findings in the prevention of cisplatin ototoxicity.

Regulator of G protein signaling 17 represents a novel target for treating cisplatin induced hearing loss

Regulators of G protein signaling (RGS) accelerate the GTPase activity of G proteins to enable rapid termination of the signals triggered by G protein-coupled receptors (GPCRs). Activation of several GPCRs, including cannabinoid receptor 2 (CB2R) and adenosine A₁ receptor (A₁AR), protects against noise and drug-induced ototoxicity. One such drug, cisplatin, an anticancer agent used to treat various solid tumors, produces permanent hearing loss in experimental animals and in a high percentage of cancer patients who undergo treatments. In this study we show that cisplatin induces the expression of the RGS17 gene and increases the levels of RGS17 protein which contributes to a significant proportion of the hearing loss. Knockdown of RGS17 suppressed cisplatin-induced hearing loss in male Wistar rats, while overexpression of RGS17 alone produced hearing loss in vivo. Furthermore, RGS17 and CB2R negatively regulate the expression of each other. These data suggest that RGS17 mediates cisplatin ototoxicity by uncoupling cytoprotective GPCRs from their normal G protein interactions, thereby mitigating the otoprotective contributions of endogenous ligands of these receptors. Thus, RGS17 represents a novel mediator of cisplatin ototoxicity and a potential therapeutic target for treating hearing loss.

Ototoxicity of Non-aminoglycoside Antibiotics

It is well-known that aminoglycoside antibiotics can cause significant hearing loss and vestibular deficits that have been described in animal studies and in clinical reports. The purpose of this review is to summarize relevant preclinical and clinical publications that discuss the ototoxicity of non-aminoglycoside antibiotics. The major classes of antibiotics other than aminoglycosides that have been associated with hearing loss in animal studies and in patients are discussed in this report. These antibiotics include: capreomycin, a polypeptide antibiotic that has been used to treat patients with drug-resistant tuberculosis, particularly in developing nations; the macrolides, including erythromycin, azithromycin and clarithromycin; and vancomycin. These antibiotics have been associated with ototoxicity, particularly in neonates. It is critical to be aware of the ototoxic potential of these antibiotics since so much attention has been given to the ototoxicity of aminoglycoside antibiotics in the literature.

Lmo4 Deficiency Enhances Susceptibility to Cisplatin-Induced Cochlear Apoptosis and Hearing Loss

Cisplatin, a potent chemotherapeutic drug, induces ototoxicity, which limits its clinical utility. Cisplatin-induced oxidative stress plays a causal role in cochlear apoptosis while the consequent nitrative stress leads to the nitration of LIM domain only 4 (LMO4), a transcriptional regulator, and decreases its cochlear expression levels. Here, we show a direct link between cochlear LMO4 and cisplatin-induced hearing loss by employing a Lmo4 conditional knockout mouse model (Lmo4^lox/lox; Gfi1^Cre/+). Hair cell-specific deletion of Lmo4 did not alter cochlear morphology or affect hearing thresholds and otoacoustic emissions, in the absence of apoptotic stimuli. Cisplatin treatment significantly elevated the auditory brainstem response thresholds of conditional knockouts, across all frequencies. Moreover, deletion of Lmo4 compromised the activation of STAT3, a downstream target that regulates anti-apoptotic machinery. Immunostaining indicated that the expression of phosphorylated STAT3 was significantly decreased while the expression of activated caspase 3 was significantly increased in Lmo4 deficient hair cells, post-cisplatin treatment. These findings suggest an otoprotective role of LMO4 as cisplatin-induced decrease in cochlear LMO4 could compromise the LMO4/STAT3 cellular defense mechanism to induce ototoxicity.

Unravelling the cooperative role of lattice strain on MnO2/TiO2 and MnO2/ZnO catalysts for the fast decomposition of hydrogen peroxide

The rate of decomposition of hydrogen peroxide was directly correlated with lattice strain, as derived from strain calculations.

Influence of lattice strain on Fe3O4@carbon catalyst for the destruction of organic dye in polluted water using a combined adsorption and Fenton process

In this study, 8, 25 and 50 wt% Fe3O4@activated carbon (AC) catalysts were prepared by simple coprecipitation method. The efficiency of the catalysts for the advanced Fenton's oxidation process using methylene blue (MB) as a model substrate was tested. Both modified and unmodified activated carbon catalysts exhibited similar activity towards the Fenton's oxidation process. Therefore, it is difficult to identify the role of the catalyst in this dye removal process. Hence, we proposed a new methodology to remove the MB by adopting the adsorption process initially, followed by the Fenton's oxidation process. The proposed process significantly improved the methylene blue decomposition reaction over the 25 wt% Fe3O4@AC catalyst. However, this trend was not seen in pure activated carbon and Fe3O4@AC (8 and 50 wt%) catalysts due to the instability of the material in the oxidizing medium. The possible reason for the deactivation of the catalysts was evaluated from lattice strain calculations, as derived from the modified W-H models (Uniform Deformational Model (UDM), Uniform Stress Deformation Model (USDM) and Uniform Deformation Energy Density Model (UDEDM)). These results provided a quantitative relationship between the experimentally calculated lattice strain values and Fenton's catalytic activity. Furthermore, the optimized strain value and crystalite size of Fe3O4 on the activated carbon matrix are responsible for the high catalytic activity.

Strategies to reduce the risk of platinum containing antineoplastic drug-induced ototoxicity

INTRODUCTION

Cisplatin is a highly effective chemotherapeutic agent against a variety of solid tumors in adults and in children. Unfortunately, a large percentage of patients suffer permanent sensorineural hearing loss. Up to 60% of children and at least 50% of adults suffer this complication that seriously compromises their quality of life. Hearing loss is due to damage to the sensory cells in the inner ear. The mechanisms of cochlear damage are still being investigated. However, it appears that inner ear damage is triggered by reactive oxygen species (ROS) formation and inflammation 34.

AREAS COVERED

We discuss a number of potential therapeutic targets that can be addressed to provide hearing protection. These strategies include enhancing the endogenous antioxidant pathways, heat shock proteins, G protein coupled receptors and counteracting ROS and reactive nitrogen species, and blocking pathways that produce inflammation, including TRPV1 and STAT1 36.

EXPERT OPINION

Numerous potential protective agents show promise in animal models by systemic or local administration. However, clinical trials have not shown much efficacy to date with the exception of sodium thiosulfate. There is an urgent need to discover safe and effective protective agents that do not interfere with the efficacy of cisplatin against tumors yet preserve hearing 151.

Targeting Inflammatory Processes Mediated by TRPVI and TNF-α for Treating Noise-Induced Hearing Loss

Noise trauma is the most common cause of hearing loss in adults. There are no known FDA approved drugs for prevention or rescue of noise-induced hearing loss (NIHL). In this study, we provide evidence that implicates stress signaling molecules (TRPV1, NOX3, and TNF-α) in NIHL. Furthermore, we provide evidence that inhibiting any one of these moieties can prevent and treat NIHL when administered within a window period. Hearing loss induced by loud noise is associated with the generation of reactive oxygen species (ROS), increased calcium (Ca²⁺) in the endolymph and hair cells, and increased inflammation in the cochlea. Increased (Ca²⁺) and ROS activity persists for several days after traumatic noise exposure (NE). Chronic increases in (Ca²⁺) and ROS have been shown to increase inflammation and apoptosis in various tissue. However, the precise role of Ca²⁺ up-regulation and the resulting inflammation causing a positive feedback loop in the noise-exposed cochlea to generate sustained toxic amounts of Ca²⁺ are unknown. Here we show cochlear TRPV1 dysregulation is a key step in NIHL, and that inflammatory TNF-α cytokine-mediated potentiation of TRPV1 induced Ca²⁺ entry is an essential mechanism of NIHL. In the Wistar rat model, noise produces an acute (within 48 h) and a chronic (within 21 days) increase in cochlear gene expression of TRPV1, NADPH oxidase 3 (NOX3) and pro-inflammatory mediators such as tumor necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX2). Additionally, we also show that H₂O₂ (100 μM) produces a robust increase in Ca²⁺ entry in cell cultures which is enhanced by TNF-α via the TRPV1 channel and which involves ERK1/2 phosphorylation. Mitigation of NIHL could be achieved by using capsaicin (TRPV1 agonist that rapidly desensitizes TRPV1. This mechanism is used in the treatment of pain in diabetic peripheral neuropathy) pretreatment or by inhibition of TNF-α with Etanercept (ETA), administered up to 7 days prior to NE or within 24 h of noise. Our results demonstrate the importance of the synergistic interaction between TNF-α and TRPV1 in the cochlea and suggest that these are important therapeutic targets for treating NIHL.

Local Drug Delivery for Prevention of Hearing Loss

Systemic delivery of therapeutics for targeting the cochlea to prevent or treat hearing loss is challenging. Systemic drugs have to cross the blood-labyrinth barrier (BLB). BLB can significantly prevent effective penetration of drugs in appropriate concentrations to protect against hearing loss caused by inflammation, ototoxic drugs, or acoustic trauma. This obstacle may be obviated by local administration of protective agents. This route can deliver higher concentration of drug compared to systemic application and preclude systemic side effects. Protective agents have been administered by intra-tympanic injection in numerous preclinical studies. Drugs such as steroids, etanercept, D and L-methionine, pifithrin-alpha, adenosine agonists, melatonin, kenpaullone (a cyclin-dependent kinase 2 (CDK2) inhibitor) have been reported to show efficacy against cisplatin ototoxicity in animal models. Several siRNAs have been shown to ameliorate cisplatin ototoxicity when administered by intra-tympanic injection. The application of corticosteroids and a number of other drugs with adjuvants appears to enhance efficacy. Administration of siRNAs to knock down AMPK kinase, liver kinase B1 (LKB1) or G9a in the cochlea have been found to ameliorate noise-induced hearing loss. The local administration of these compounds appears to be effective in protecting the cochlea against damage from cisplatin or noise trauma. Furthermore the intra-tympanic route yields maximum protection in the basal turn of the cochlea which is most vulnerable to cisplatin ototoxicity and noise trauma. There appears to be very little transfer of these agents to the systemic circulation. This would avoid potential side effects including interference with anti-tumor efficacy of cisplatin. Nanotechnology offers strategies to effectively deliver protective agents to the cochlea. This review summarizes the pharmacology of local drug delivery by intra-tympanic injection to prevent hearing loss caused by cisplatin and noise exposure in animals. Future refinements in local protective agents provide exciting prospects for amelioration of hearing loss resulting from cisplatin or noise exposure.

Oral Administration of Caffeine Exacerbates Cisplatin-Induced Hearing Loss

Adenosine A₁ receptors (A₁AR) are well characterized for their role in cytoprotection. Previous studies have demonstrated the presence of these receptors in the cochlea where their activation were shown to suppress cisplatin-induced inflammatory response and the resulting ototoxicity. Inhibition of A₁AR by caffeine, a widely consumed psychoactive substance, could antagonize the endogenous protective role of these receptors in cochlea and potentiate cisplatin-induced hearing loss. This hypothesis was tested in a rat model of cisplatin ototoxicity following oral administration of caffeine. We report here that single-dose administration of caffeine exacerbates cisplatin-induced hearing loss without increasing the damage to outer hair cells (OHCs), but increased synaptopathy and inflammation in the cochlea. These effects of caffeine were mediated by its blockade of A₁AR, as co-administration of R-PIA, an A₁AR agonist, reversed the detrimental actions of caffeine and cisplatin on hearing loss. Multiple doses of caffeine exacerbated cisplatin ototoxicity which was associated with damage to OHCs and cochlear synaptopathy. These findings highlight a possible drug-drug interaction between caffeine and cisplatin for ototoxicity and suggest that caffeine consumption should be cautioned in cancer patients treated with a chemotherapeutic regimen containing cisplatin.

Mechanisms of Cisplatin-Induced Ototoxicity and Prevention

Cisplatin is a highly effective antineoplastic agent used to treat solid tumors. Unfortunately, the administration of this drug leads to significant side effects, including ototoxicity, nephrotoxicity, and neurotoxicity. This review addresses the mechanisms of cisplatin-induced ototoxicity and various strategies tested to prevent this distressing adverse effect. The molecular pathways underlying cisplatin ototoxicity are still being investigated. Cisplatin enters targeted cells in the cochlea through the action of several transporters. Once it enters the cochlea, cisplatin is retained for months to years. It can cause DNA damage, inhibit protein synthesis, and generate reactive oxygen species that can lead to inflammation and apoptosis of outer hair cells, resulting in permanent hearing loss. Strategies to prevent cisplatin ototoxicity have utilized antioxidants, transport inhibitors, G-protein receptor agonists, and anti-inflammatory agents. There are no FDA-approved drugs to prevent cisplatin ototoxicity. It is critical that potential protective agents do not interfere with the antitumor efficacy of cisplatin.

The Endocannabinoid/Cannabinoid Receptor 2 System Protects Against Cisplatin-Induced Hearing Loss

Previous studies have demonstrated the presence of cannabinoid 2 receptor (CB2R) in the rat cochlea which was induced by cisplatin. In an organ of Corti-derived cell culture model, it was also shown that an agonist of the CB2R protected these cells against cisplatin-induced apoptosis. In the current study, we determined the distribution of CB2R in the mouse and rat cochleae and examined whether these receptors provide protection against cisplatin-induced hearing loss. In a knock-in mouse model expressing the CB2R tagged with green fluorescent protein, we show distribution of CB2R in the organ of Corti, stria vascularis, spiral ligament and spiral ganglion cells. A similar distribution of CB2R was observed in the rat cochlea using a polyclonal antibody against CB2R. Trans-tympanic administration of (2-methyl-1-propyl-1H-indol-3-yl)-1-naphthalenylmethanone (JWH015), a selective agonist of the CB2R, protected against cisplatin-induced hearing loss which was reversed by blockade of this receptor with 6-iodo-2-methyl-1-[2-(4-morpholinyl)ethyl]-1H-indol-3-yl](4-methoxyphenyl)methanone (AM630), an antagonist of CB2R. JWH015 also reduced the loss of outer hair cells (OHCs) in the organ of Corti, loss of inner hair cell (IHC) ribbon synapses and loss of Na⁺/K⁺-ATPase immunoreactivity in the stria vascularis. Administration of AM630 alone produced significant hearing loss (measured by auditory brainstem responses) which was not associated with loss of OHCs, but led to reductions in the levels of IHC ribbon synapses and strial Na⁺/K⁺-ATPase immunoreactivity. Furthermore, knock-down of CB2R by trans-tympanic administration of siRNA sensitized the cochlea to cisplatin-induced hearing loss at the low and middle frequencies. Hearing loss induced by cisplatin and AM630 in the rat was associated with increased expression of genes for oxidative stress and inflammatory proteins in the rat cochlea. In vitro studies indicate that JWH015 did not alter cisplatin-induced killing of cancer cells suggesting this agent could be safely used during cisplatin chemotherapy. These data unmask a protective role of the cochlear endocannabinoid/CB2R system which appears tonically active under normal conditions to preserve normal hearing. However, an exogenous agonist is needed to boost the activity of endocannabinoid/CB2R system for protection against a more traumatic cochlear insult, as observed with cisplatin administration.

Trans-Tympanic Drug Delivery for the Treatment of Ototoxicity

The systemic administration of protective agents to treat drug-induced ototoxicity is limited by the possibility that these protective agents could interfere with the chemotherapeutic efficacy of the primary drugs. This is especially true for the drug cisplatin, whose anticancer actions are attenuated by antioxidants which provide adequate protection against hearing loss. Other current or potential otoprotective agents could pose a similar problem, if administered systemically. The application of various biologicals or protective agents directly to the cochlea would allow for high levels of these agents locally with limited systemic side effects. In this report, we demonstrate a trans-tympanic method of delivery of various drugs or biological reagents to the cochlea, which should enhance basic science research on the cochlea and provide a simple way of directing the use of otoprotective agents in the clinics. This report details a method of trans-tympanic drug delivery and provides examples of how this technique has been used successfully in experimental animals to treat cisplatin ototoxicity.

Mechanisms of Cisplatin-Induced Ototoxicity and Otoprotection

Evidence of significant hearing loss during the early days of use of cisplatin as a chemotherapeutic agent in cancer patients has stimulated research into the causes and treatment of this side effect. It has generally been accepted that hearing loss is produced by excessive generation of reactive oxygen species (ROS) in cell of the cochlea, which led to the development of various antioxidants as otoprotective agents. Later studies show that ROS could stimulate cochlear inflammation, suggesting the use of anti-inflammatory agents for treatment of hearing loss. In this respect, G-protein coupled receptors, such as adenosine A₁ receptor and cannabinoid 2 receptors, have shown efficacy in the treatment of hearing loss in experimental animals by increasing ROS scavenging, suppressing ROS generation, or by decreasing inflammation. Inflammation could be triggered by activation of transient receptor potential vanilloid 1 (TRPV1) channels in the cochlea and possibly other TRP channels. Targeting TRPV1 for knockdown has also been shown to be a useful strategy for ensuring otoprotection. Cisplatin entry into cochlear hair cells is mediated by various transporters, inhibitors of which have been shown to be effective for treating hearing loss. Finally, cisplatin-induced DNA damage and activation of the apoptotic process could be targeted for cisplatin-induced hearing loss. This review focuses on recent development in our understanding of the mechanisms underlying cisplatin-induced hearing loss and provides examples of how drug therapies have been formulated based on these mechanisms.

Epigallocatechin-3-gallate, a prototypic chemopreventative agent for protection against cisplatin-based ototoxicity

Cisplatin-induced ototoxicity is one of the major factors limiting cisplatin chemotherapy. Ototoxicity results from damage to outer hair cells (OHCs) and other regions of the cochlea. At the cellular level, cisplatin increases reactive oxygen species (ROS) leading to cochlear inflammation and apoptosis. Thus, ideal otoprotective drugs should target oxidative stress and inflammatory mechanisms without interfering with cisplatin's chemotherapeutic efficacy. In this study, we show that epigallocatechin-3-gallate (EGCG) is a prototypic agent exhibiting these properties of an effect otoprotective agent. Rats administered oral EGCG demonstrate reduced cisplatin-induced hearing loss, reduced loss of OHCs in the basal region of the cochlea and reduced oxidative stress and apoptotic markers. EGCG also protected against the loss of ribbon synapses associated with inner hair cells and Na⁺/K⁺ ATPase α1 in the stria vascularis and spiral ligament. In vitro studies showed that EGCG reduced cisplatin-induced ROS generation and ERK1/2 and signal transducer and activator of transcription-1 (STAT1) activity, but preserved the activity of STAT3 and Bcl-xL. The increase in STAT3/STAT1 ratio appears critical for mediating its otoprotection. EGCG did not alter cisplatin-induced apoptosis of human-derived cancer cells or cisplatin antitumor efficacy in a xenograft tumor model in mice because of its inability to rescue the downregulation of STAT3 in these cells. These data suggest that EGCG is an ideal otoprotective agent for treating cisplatin-induced hearing loss without compromising its antitumor efficacy.

Tonic suppression of PCAT29 by the IL-6 signaling pathway in prostate cancer: Reversal by resveratrol

Prostate cancer (PCa) is the second leading cause of cancer deaths in men. A better understanding of the molecular basis of prostate cancer proliferation and metastasis should enable development of more effective treatments. In this study we focused on the lncRNA, prostate cancer associated transcript 29 (PCAT29), a putative tumor suppressive gene. Our data show that the expression of PCAT29 was reduced in prostate cancer tumors compared to paired perinormal prostate tissues. We also observed substantially lower levels of PCAT29 in DU145 and LNCaP cells compared to normal prostate (RWPE-1) cells. IL-6, a cytokine which is elevated in prostate tumors, reduced the expression of PCAT29 in both DU145 and LNCaP cells by activating signal transducer and activator of transcription 3 (STAT3). One downstream target of STAT3 is microRNA (miR)-21, inhibition of which enhanced basal PCAT29 expression. In addition, we show that resveratrol is a potent stimulator of PCAT29 expression under basal condition and reversed the down regulation of this lncRNA by IL-6. Furthermore, we show that knock down of PCAT29 expression by siRNA in DU145 and LNCaP cells increased cell viability while increasing PCAT29 expression with resveratrol decreased cell viability. Immunohistochemistry studies showed increased levels of STAT3 and IL-6, but low levels of programmed cell death protein 4 (PDCD4), in prostate tumor epithelial cells compared to adjacent perinormal prostate epithelial cells. These data show that the IL-6/STAT3/miR-21 pathway mediates tonic suppression of PCAT29 expression and function. Inhibition of this signaling pathway by resveratrol induces PCAT29 expression and tumor suppressor function.

3-Benzylidene-1′-methyl-4′-phenyldispiro[cyclopentane-1,3′-pyrrolidine-2′,1′′-acenaphthene]-2,2′′-dione

In the title compound, C33H27NO2, the pyrrolidine ring adopts an envelope conformation, with the N atom as the flap. The cyclopentanone ring adopts a twisted conformation about the Cs—CH2bond (s = spiro link). The dihedral angle between these rings (all atoms) is 82.02 (15)°. The packing features weak C—H...O interactions.

Adenosine A1 Receptor Protects Against Cisplatin Ototoxicity by Suppressing the NOX3/STAT1 Inflammatory Pathway in the Cochlea

Cisplatin is a commonly used antineoplastic agent that produces ototoxicity that is mediated in part by increasing levels of reactive oxygen species (ROS) via the NOX3 NADPH oxidase pathway in the cochlea. Recent studies implicate ROS generation in mediating inflammatory and apoptotic processes and hearing loss by activating signal transducer and activator of transcription (STAT1). In this study, we show that the adenosine A1 receptor (A1AR) protects against cisplatin ototoxicity by suppressing an inflammatory response initiated by ROS generation via NOX3 NADPH oxidase, leading to inhibition of STAT1. Trans-tympanic administration of the A1AR agonist R-phenylisopropyladenosine (R-PIA) inhibited cisplatin-induced ototoxicity, as measured by auditory brainstem responses and scanning electron microscopy in male Wistar rats. This was associated with reduced NOX3 expression, STAT1 activation, tumor necrosis factor-α (TNF-α) levels, and apoptosis in the cochlea. In vitro studies in UB/OC-1 cells, an organ of Corti immortalized cell line, showed that R-PIA reduced cisplatin-induced phosphorylation of STAT1 Ser(727) (but not Tyr(701)) and STAT1 luciferase activity by suppressing the ERK1/2, p38, and JNK mitogen-activated protein kinase (MAPK) pathways.R-PIA also decreased the expression of STAT1 target genes, such as TNF-α, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) and reduced cisplatin-mediated apoptosis. These data suggest that the A1AR provides otoprotection by suppressing NOX3 and inflammation in the cochlea and could serve as an ideal target for otoprotective drug therapy.

SIGNIFICANCE STATEMENT

Cisplatin is a widely used chemotherapeutic agent for the treatment of solid tumors. Its use results in significant and permanent hearing loss, for which no US Food and Drug Administration-approved treatment is currently available. In this study, we targeted the cochlear adenosine A1 receptor (A1AR) by trans-tympanic injections of the agonist R-phenylisopropyladenosine (R-PIA) and showed that it reduced cisplatin-induced inflammation and apoptosis in the rat cochlea and preserved hearing. The mechanism of protection involves suppression of the NOX3 NADPH oxidase enzyme, a major target of cisplatin-induced reactive oxygen species (ROS) generation in the cochlea. ROS initiates an inflammatory and apoptotic cascade in the cochlea by activating STAT1 transcription factor, which is attenuated byR-PIA. Therefore, trans-tympanic delivery of A1AR agonists could effectively treat cisplatin ototoxicity.

Substitution effect on chalcone based materials for corrosion and photocrosslinking applications

Hydroxy (–OH) and benzyloxy (–OCH₂Ph) substituted chalcone based crystalline materials were synthesized and characterized; these materials exhibited high corrosion inhibitor efficiency and enhanced photo-crosslinking applications.

Crystal structure of 2,4-bis-(2-chloro-phen-yl)-7-tert-pent-yl-3-aza-bicyclo[3.3.1]nonan-9-one

The title compound, C₂₅H₂₉Cl₂NO, which is a chloro analog of 2,4-bis­(2-bromo­phen­yl)-7-(tert-pent­yl)-3-aza­bicyclo­[3.3.1]nonan-9-one [Park, Ramkumar & Parthiban (2012). Acta Cryst. E68, o2946], exists in a twin-chair conformation with an equatorial orientation of the 2-chloro­phenyl groups. The tert-pentyl group on the cyclo­hexa­none adopts an exocyclic equatorial position and is disordered between two orientations in a ratio 0.520 (8):0.480 (8). The crystal packing shows no directional contacts beyond van der Waals contacts.

Crystal structure of 2,6-bis-(2,5-di-meth-oxy-phen-yl)-3,5-di-methyl-piperidin-4-one

In the title mol-ecule, C23H29NO5, the central piperidine ring has a chair conformation. The planes of the two benzene rings are inclined each to other at 61.7 (1)°. The crystal packing exhibits no directional inter-actions only van der Waals contacts.

Early investigational drugs for hearing loss

INTRODUCTION

Sensorineural hearing loss (HL) is becoming a global phenomenon at an alarming rate. Nearly 600 million people have been estimated to have significant HL in at least one ear. There are several different causes of sensorineural HL included in this review of new investigational drugs for HL. They are noise-induced, drug-induced, sudden sensorineural HL, presbycusis and HL due to cytomegalovirus infections.

AREAS COVERED

This review presents trends in research for new investigational drugs encompassing a variety of causes of HL. The studies presented here are the latest developments either in the research laboratories or in preclinical, Phase 0, Phase I or Phase II clinical trials for drugs targeting HL.

EXPERT OPINION

While it is important that prophylactic measures are developed, it is extremely crucial that rescue strategies for unexpected or unavoidable cochlear insult be established. To achieve this goal for the development of drugs for HL, innovative strategies and extensive testing are required for progress from the bench to bedside. However, although a great deal of research needs to be done to achieve the ultimate goal of protecting the ear against acquired sensorineural HL, we are likely to see exciting breakthroughs in the near future.

TRPV1: A Potential Drug Target for Treating Various Diseases

Transient receptor potential vanilloid 1 (TRPV1) is an ion channel present on sensory neurons which is activated by heat, protons, capsaicin and a variety of endogenous lipids termed endovanilloids. As such, TRPV1 serves as a multimodal sensor of noxious stimuli which could trigger counteractive measures to avoid pain and injury. Activation of TRPV1 has been linked to chronic inflammatory pain conditions and peripheral neuropathy, as observed in diabetes. Expression of TRPV1 is also observed in non-neuronal sites such as the epithelium of bladder and lungs and in hair cells of the cochlea. At these sites, activation of TRPV1 has been implicated in the pathophysiology of diseases such as cystitis, asthma and hearing loss. Therefore, drugs which could modulate TRPV1 channel activity could be useful for the treatment of conditions ranging from chronic pain to hearing loss. This review describes the roles of TRPV1 in the normal physiology and pathophysiology of selected organs of the body and highlights how drugs targeting this channel could be important clinically.

1'-Allyl-1-(3,4-di-methyl-benzo-yl)-2-(4-methyl-1,3-thia-zol-5-yl)-1,2,5,6,7,7a-hexa-hydro-spiro-[pyrrolizine-3,3'-indolin]-2'-one

In the title compound, C₃₀H₃₁N₃O₂S, the fused pyrrolidine ring bearing three substituents adopts an envelope conformation with the C atom bearing the benzoyl group as the flap. The other fused pyrrolidine ring adopts a twisted conformation about one of its C—C bonds. The dihedral angle between the isatin ring system and the methyl­thia­zole ring is 25.95 (8)°. An intra­molecular C—H⋯O inter­action closes an S(8) ring. In the crystal, mol­ecules are linked by C—H⋯O inter­actions, generating C(11) chains propagating in [001].

Adenosine receptors: expression, function and regulation

Adenosine receptors (ARs) comprise a group of G protein-coupled receptors (GPCR) which mediate the physiological actions of adenosine. To date, four AR subtypes have been cloned and identified in different tissues. These receptors have distinct localization, signal transduction pathways and different means of regulation upon exposure to agonists. This review will describe the biochemical characteristics and signaling cascade associated with each receptor and provide insight into how these receptors are regulated in response to agonists. A key property of some of these receptors is their ability to serve as sensors of cellular oxidative stress, which is transmitted by transcription factors, such as nuclear factor (NF)-κB, to regulate the expression of ARs. Recent observations of oligomerization of these receptors into homo- and heterodimers will be discussed. In addition, the importance of these receptors in the regulation of normal and pathological processes such as sleep, the development of cancers and in protection against hearing loss will be examined.

2-[(E)-2-(4-Methoxyphenyl)ethenyl]-1-methylpyridinium iodide

In the title mol­ecular salt, C₁₆H₁₀NO⁺·I⁻, the dihedral angle between the pyridinium and benzene rings is 6.61 (8)°. In the crystal, the cation is linked to the anion by a C—H⋯I inter­action arising from the activated aromatic C atom adjacent to the N⁺ cation.

Essential role of NADPH oxidase-dependent reactive oxygen species generation in regulating microRNA-21 expression and function in prostate cancer

AIMS

Oncogenic microRNAs (miRs) promote tumor growth and invasiveness. One of these, miR-21, contributes to carcinogenesis in prostate and other cancers. In the present study, we tested the hypothesis that NADPH oxidase-dependent reactive oxygen species (ROS) regulate the expression and function of miR-21 and its target proteins, maspin and programmed cell death 4 (PDCD4), in prostate cancer cells.

RESULTS

The highly aggressive androgen receptor negative PC-3M-MM2 prostate cancer cells demonstrated high expression of miR-21 and p47(phox) (an essential subunit of NADPH oxidase). Using loss-of-function strategy, we showed that transfection of PC-3M-MM2 cells with anti-miR-21- and p47(phox) siRNA (si-p47(phox)) led to reduced expression of miR-21 with concurrent increase in maspin and PDCD4, and decreased the invasiveness of the cells. Tail-vein injections of anti-miR-21- and si-p47(phox)-transfected PC-3M-MM2 cells in severe combined immunodeficient mice reduced lung metastases. Clinical samples from patients with advanced prostate cancer expressed high levels of miR-21 and p47(phox), and low expression of maspin and PDCD4. Finally, ROS activated Akt in these cells, the inhibition of which reduced miR-21 expression.

INNOVATION

The levels of NADPH oxidase-derived ROS are high in prostate cancer cells, which have been shown to be involved in their growth and migration. This study demonstrates that ROS produced by this pathway is essential for the expression and function of an onco-miR, miR-21, in androgen receptor-negative prostate cancer cells.

CONCLUSION

These data demonstrate that miR-21 is an important target of ROS, which contributes to the highly invasive and metastatic phenotype of prostate cancer cells.

Intestinal infestation with Fasciolopsis buski leading to acute kidney injury

Fasciolopsis buski is the largest intestinal fluke infecting human beings. This trematode is endemic in certain parts of the country. Migration poses the risk of spread of the worm to other parts of the country. We report fasciolopsis buski in a migrant from Bihar working in Coimbatore, Tamil Nadu. Acute kidney injury following intestinal obstruction occurred in this case which was never described before.

2,2'-{[(1E,1'E)-(Cyclo-hexane-1,4-diyl)-bis(aza-nylyl-idene)]bis-(ethan-1-yl-1-yl-idene)}diphenol

The title compound, C22H26N2O2, crystallizes with three independent mol-ecules, two of which are situated on inversion centers, so the asymmetric unit contains two independent half-mol-ecules and one mol-ecule in a general position. The two hy-droxy groups in each mol-ecule are involved in intra-molecular O-H⋯N hydrogen bonds, which generate S(6) rings. In the crystal, weak inter-molecular C-H⋯π inter-actions link the mol-ecules into two crystallographically independent columns propagating along [001]; one column consists of mol-ecules in general positions, while the other column is built from alternating independent centrosymmetric mol-ecules.

μ-(2,6-Bis{[3-(di-methyl-amino)-prop-yl]imino-meth-yl}-4-methyl-phenolato)-μ-hydroxido-bis-[(thio-cyanato-κN)copper(II)]

In the title compound, [Cu2(C19H31N4O)(OH)(NCS)2], the mol-ecular structure of the dinuclear complex reveals two penta-coordinated Cu(II) ions, which are bridged by the phenolate O atom of the ligand and by an exogenous hydroxide ion. The bridging atoms occupy equatorial positions in the coordination sphere of the metal atoms and complete the equatorial coordination planes with two ligand N atoms, the apical positions being occupied by thio-cyanate N atoms. The crystal structure also features π-π stacking inter-actions involving the benzene rings with a centroid-centroid distance of 3.764 (4)Å. The crystal studied was a non-merohedral twin, with a refined BASF value of 0.203 (2).

Ethyl 2-amino-4-(4-methyl-1,3-thia-zol-5-yl)-5-oxo-4H,5H-pyrano[3,2-c]chromene-3-carboxyl-ate

There are two independent mol-ecules in the asymmetric unit of the title compound, C19H16N2O5S, in which the thia-zole rings make dihedral angles of 80.89 (11) and 84.81 (11)° with the pyrano[3,2-c]chromene ring systems. An intra-molecular N-H⋯O hydrogen bond involving the amino group occurs in each independent mol-ecule. In the crystal, the amino groups are involved in N-H⋯O and N-H⋯N hydrogen bonds.

1,3-Bis(2-methyl-prop-2-eno-yl)-1H-benz-imidazol-2(3H)-one

The mol-ecules of the title compound, C15H14N2O3, possesses crystallographically imposed twofold rotational symmetry, so the asymmetric unit contains one half-mol-ecule. The fused-ring system deviates significantly from planarity; the planes of the five- and six-membered rings are twisted with respect to each other by 3.0 (1)°. In the crystal, weak C-H⋯O hydrogen bonds link mol-ecules related by translation in [010] into chains.

Abstract 4084: Resveratrol attenuates prostate cancer growth by inhibiting insulin-like growth factor-1 receptor signaling

Introduction: Prostate cancer is the most commonly diagnosed cancer in the United States. The etiology of prostate cancer development and progression is not very clear. Accumulating evidence suggests that an elevated level of insulin-like growth factor-1 (IGF-1) is positively associated with the growth of prostate cancer. IGF-1 exerts its mitogenic effect by binding to its receptor, IGF-1R, whose expression is also increased during tumor growth. Resveratrol, a phytoalexin, has been shown to possess anti-cancer action against various cancers through unknown mechanism/s. In this study, we examined whether resveratrol mediates its anti-tumor effects by inhibiting the trophic actions of IGF-1/IGF-1R on prostate cancer.

Methods: In vitro studies were performed on highly aggressive androgen receptor negative human prostate cancer cells, PC-3M-MM2. Cell viability was assessed by MTS assays, while apoptosis was determined by Annexin-FITC and PI staining. Additionally, ELISA and western blotting techniques were performed to examine the levels of IGF-1 and protein involved in IGF-axis, respectively. In vivo efficacy of resveratrol was tested in a xenograft model of prostate cancer in severe combined immunodeficient (SCID) mice. PC-3M-MM2 cells were subcutaneously injected in these mice and resveratrol was administered by oral gavage for the assessment of tumor growth. Primary tumors were then excised and immunohistochemistry was performed on the tumor sections. Results: Resveratrol significantly inhibited the release of IGF-1 from PC-3M-MM2 cells and reduced the activation of IGF-1R. Inhibition of IGF-1R by resveratrol suppressed the activation of Akt (pAkt) and increased the expression of programmed cell death 4 (PDCD4), a pro-apoptotic protein and a target of Akt. These effects of resveratrol were associated with reduced cell viability and induction of apoptosis in PC-3M-MM2 cells. Treatment of cells with short interfering (si) RNA against IGF-1R or PI3 kinase inhibitor (LY294002) mimicked the response of resveratrol on cell viability, apoptosis and the expression of pAkt and PDCD4. Furthermore, oral administration of resveratrol in SCID mice that were subcutaneously injected with PC-3M-MM2 cells suppressed subsequent tumor growth. Resveratrol also reduced serum and tumor levels of IGF-1 and inhibited the activation of IGF-1R in these tumors. This modulation of IGF-1/IGF-1R coincided with the inhibition of pAkt and increase in PDCD4 in the tumor tissue.

Conclusion: Our results indicate that resveratrol effectively suppressed prostate cancer growth in vitro as well as in vivo by attenuating IGF-1/IGF-1R signaling pathway. These data demonstrate that the IGF/IGF-1R represent a relevant target of resveratrol for mediating its anti-tumor actions against prostate cancer.

Citation Format: Sandeep Sheth, Sarvesh Jajoo, Debashree Mukherjea, Kelly Sheehan, Leonard P. Rybak, Vickram Ramkumar. Resveratrol attenuates prostate cancer growth by inhibiting insulin-like growth factor-1 receptor signaling. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4084. doi:10.1158/1538-7445.AM2013-4084