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Introduction Based on our preliminary 11C-nicotine positron emission tomography (PET) imaging studies in humans, we speculated that greater deposition of nicotine in the respiratory tract from electronic cigarettes compared to combustible cigarettes could result from the alkaline pH of typical aerosol-producing electronic cigarette liquids (e-liquids). To address this hypothesis, we assessed the effect of e-liquid pH on the retention of nicotine in vitro using 11C-nicotine, PET, and a human respiratory tract model of nicotine deposition. Aims and Methods A single 2-second 35-mL puff was delivered to a human respiratory tract cast from a 2.8-Ohm cartomizer at 4.1 volts. Immediately after the puff, a 2-second 700-mL air wash-in volume was administered. E-liquids (glycerol and propylene glycol 50/50 vol/vol) containing 24 mg/mL nicotine were mixed with 11C-nicotine. Deposition (retention) of nicotine was assessed using a GE Discovery MI DR PET/CT scanner. Eight e-liquids with different pH values (range 5.3–9.6) were investigated. All experiments were performed at room temperature and at a relative humidity of 70%–80%. Results Retention of nicotine in the respiratory tract cast was pH dependent and the pH-sensitive component of the retention was well described by a sigmoid curve. In total, 50% of the maximal pH-dependent effect was observed at pH 8.0, which is close to the pKa2 of nicotine. Conclusions The retention of nicotine in the respiratory tract conducting airways is dependent on the e-liquid pH. Lowering the e-liquid pH reduces retention of nicotine. Nonetheless, reduction of the pH below 7 has little effect, consistent with the pKa2 of protonated nicotine. Implications Similar to combustible cigarettes, the retention of nicotine in the human respiratory tract from consumption of electronic cigarettes may have some health consequences and affect nicotine dependence. Here we demonstrated that the retention of nicotine in the respiratory tract is dependent on the e-liquid pH, and lowering pH reduces retention of nicotine in conducting airways of the respiratory tract. Therefore, e-cigarettes with low pH values would result in reduced respiratory tract nicotine exposure and faster delivery of nicotine to the central nervous system (CNS). The latter can be associated with e-cigarette abuse liability and the effectiveness of e-cigarettes as substitutes for combustible cigarettes.

Most individuals with cocaine use disorder also use alcohol; however, little is known about the behavioural and pharmacological mechanisms that promote co-abuse. For example, although studies in humans and animals have documented that chronic use of either alcohol or cocaine alone decreases D2-like receptor (D2R) availability, effects of co-abuse of these substances on dopamine receptor function have not been characterized. These studies examined the effects of long-term cocaine self-administration in 12 male rhesus monkeys who also consumed either ethanol or an ethanol-free solution each day (n = 6 per group). Specifically, all monkeys self-administered cocaine (0.1 mg/kg per injection) 5 days per week in the morning. In the afternoon, six monkeys consumed 2.0 g/kg ethanol over 1 h to model binge drinking and six monkeys drank an ethanol-free solution. Assessment of D2R availability using positron emission tomography (PET) and [

Naturally occurring colorectal cancers (CRC) in rhesus macaques share many features with their human counterparts and emerge at similar life stages as in human patients, but the carcinogenesis and molecular background remain elusive, limiting the value of the model for human disease and cancer therapy. In order to better understand this naturally occurring model, we established a diagnostic and staging pipeline including imaging (18F-FDG PET, plain and contrast-enhanced CT), histopathology, and clinical assessments. We observed cancer symptoms and co-morbidities in our cohort (n=16, all Indian-origin, 11 females, mean age at arrival 20.2y) such as hypoalbuminemia, fecal occult blood, and microcytic anemia, as frequently described in human CRC patients. Pathologically, all cancers were right-sided, involving the proximal colon and/or ileocecocolic junction, and most were densely fibrotic, restricting the colonic lumen. Most cancers appeared with glandular morphology and some (18.8%) had mucinous components. Immunohistochemistry revealed loss of MLH1 and PMS2 in 100% of investigated CRCs, indicating mismatch repair deficiency which furthermore resulted in microsatellite instability (PCR & fragment analysis). Whole exome sequencing revealed the close genetic relatedness to human CRCs, particularly exemplified by mutations affecting KRAS (37.5%, e.g., p.G12D), APC (31.3%), TP53 (18.8%, e.g. p.R175H), ARID1A (56.3%), and ALK (43.8%), as similarly annotated in the human COSMIC database. Nonetheless, somatic mutations do not explain the loss of MLH1 in the entire CRC cohort. Transcriptomics on the other hand revealed the transcriptional suppression of MLH1 but not MSH2, MSH6, or PMS2 in rhesus CRC in comparison to adjacent healthy colon. Moreover, comparison of differentially expressed gene sets of rhesus CRC with a human annotated database (IPA) confirmed the disease similarities observed clinically, genetically, and histopathologically. Subsequently, we investigated DNA methylation of the promoter region of MLH1 and retranslated markers for the CpG island methylator phenotype (CIMP) as described in human CRC. While only 56.3% of CRCs were considered CIMP positive (≥3/5 markers hypermethylated), 100% of investigated CRCs exhibited MLH1 promoter hypermethylation. As a result, epigenetic silencing is suggested to suppress MLH1 transcription, cause the loss of MLH1 protein, and drive mismatch repair deficiency and genomic instability in naturally occurring CRC in rhesus macaques. We therefore consider spontaneous, uninduced CRC in rhesus macaques, their treatment-naïve nature, and their unaltered immune competence an outstanding model for human disease and in particular for human cancer immunotherapy. Citation Format: Simon Deycmar, Brendan Johnson, Karina Ray, David Caudell Caudell, John Olson, Greg Dugan, W. Shane Sills, Declan Ryan, Christopher Whitlow, Kiran K. Solingapuram Sai, Betsy Ferguson, Benjamin Bimber, Cassandra Cullin, Brandy Dozier, Emily Romero, Francois Villinger, Armando Burgos, Jeff Chou, Bruno Gomes, Michael Hettich, Maurizio Ceppi, Jehad Charo, J. Mark Cline. Clinical and molecular characterization of naturally-occurring colorectal cancer in rhesus macaques reveals mismatch repair deficiency driven by epigenetic silencing of MLH1 [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer; 2022 Oct 1-4; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_1):Abstract nr A021.