Tobacco particulate matter is more potent than nicotine at upregulating nicotinic receptors on SH-SY5Y cells

Abstract

The effect of total particulate matter (TPM) from cigarette smoke on the expression and binding properties of nicotinic acetylcholine receptors (nAChRs) was investigated using a human neuroblastoma cell line (SH-SY5Y). TPM but not nicotine on its own inhibited cell growth at nicotine concentrations above 5 microM. To examine effects on nAChR expression, intact cells were incubated with 3H-epibatidine, and a Bmax of 13 fmoles/10(5) cells (7.8 x 10(4) binding sites/cell) was measured in unexposed cells as well as in cells treated with 2 microM nicotine alone or with TPM containing 2 microM nicotine. Using Scatchard analysis, we measured a Kd of 0.3 nM for 3H-epibatidine binding to nAChRs. This Kd was increased to 1.3 nM by addition of nicotine or TPM extract, both at 2 microM nicotine. Bmax, however, was unaffected, suggesting competitive binding of nicotine to its receptor. Short-term and prolonged 3-day exposures of SH-SY5Y cells to either TPM or nicotine at nicotine concentrations ranging from 0.2 microM to 20 microM increased specific binding, suggesting upregulation of nAChR expression. Most significant, binding was consistently greater in cells pretreated with TPM than in cells pretreated with nicotine. We conclude that TPM contains compounds that are toxic to cells at high concentrations (cell growth inhibition) but that do not compete with nicotine for binding to nAChRs (Scatchard analysis). These non-nicotinic compounds are capable of increasing the expression of one or more of the nAChR subunits. Furthermore, our cell culture assay provides a useful in vitro model for assessing the relative addictiveness of different tobacco products, including that of non-nicotine components.

Animal models to assess the abuse liability of tobacco products: Effects of smokeless tobacco extracts on intracranial self-stimulation

“…Limited data address the feasibility and utility of this approach. Delivery of nicotine in extracts can enhance its addiction-related neurobiological and behavioral effects (Ambrose et al, 2007; Brennan et al, 2013a, 2014; Costello et al, 2014; Touiki et al, 2007), consistent with the ability of certain isolated non-nicotine constituents ( e.g. , minor alkaloids) to mimic or enhance nicotine’s effects in these assays ( e.g.…”

Delivery of nicotine in an extract of a smokeless tobacco product reduces its reinforcement-attenuating and discriminative stimulus effects in rats

“…For example, tobacco or smoke extracts were more potent than nicotine alone in exerting certain neuropharmacological effects relevant to tobacco addiction (e.g., brain MAO inhibition, dopamine reuptake inhibition, 5HT neural inhibition) (Ambrose et al 2007; Carr and Basham 1991; Carr et al 1992; Touiki et al 2007), consistent with the ability of isolated constituents to enhance nicotine’s effects on these systems (e.g., Crooks and Dwoskin 1997; Foddai et al 2004; Villegier et al 2007). In addition, nicotine alone and a nicotine dose-equivalent smoke extract inhibited extinction of an avoidance task equally (Driscoll and Battig 1970), but produced opposite effects on swimming endurance in rats (Battig 1970).…”

Monoamine oxidase inhibitory activity in tobacco smoke varies with tobacco type

“…Tobacco smoke samples (tobacco particulate matter (TPM)) were produced under ISO 3308 conditions by Labstat International, Inc. (Kitchener, Canada) from each of these brands. The resulting filters holding a known amount of mainstream smoke condensate (expressed as mg of tar) were extracted with ethanol as previously described and stored at −10 to −15°C until use 11. Nicotine concentrations were determined by gas chromatography–mass spectrometry, as described 11…”