Blood-brain barrier penetration abolished by N-methyl quaternization of nicotine

Establishment of a Quantitative Method for the Extraction of Nicotine and Cotinine in Gingival Tissue and Relationship Between Gingival Intoxication With Conventional Smoking Biomarkers: A Pilot Study

OBJECTIVES

Smoking is considered a major risk factor for periodontitis genesis and progression. In clinical studies, specific indicators have been used to characterize the smoking status of the patient as the number of cigarettes consumed (NCC), the pack-years (PY), or Fagerström Test for Nicotine Dependence (FTND). However, available literature is missing on the relationship between cotinine gingival intoxication and smoking indicators. First, the development of a quantitative method for the extraction of nicotine and cotinine in gingival tissue. Second, to investigate the relationship between gingival intoxication and conventional smoking biomarkers.

MATERIAL AND METHODS

Fourteen smoker patients were included in the study. After clinical data collection, salivary and gingival samples collection, toxicological analyses were performed using liquid extraction after enzymatic digestion (subtilisin) and ultra-performance liquid chromatography coupled to mass spectrometry (UPLC-MS/MS).

RESULTS

Gingival cotinine quantification was successfully performed in 14 samples (100%) with a mean of 0.280 ng/mg (range = 0.094-0.505). Only FTND was statistically associated with gingival cotinine levels (p = 0.0072; r² = 0.60). Gingival nicotine quantification was achieved in 12 of the 14 gingival samples (86%) with a mean of 0.384 ± 1.00 ng/mg (range = 0.03-3.84). Gingival nicotine was statistically associated with NCC (p = 0.032; r² = 0.55), PY (p = 0.0011; r² = 0.76), and FTND (p = 0.016; r² = 0.60). Salivary nicotine and cotinine levels were statistically associated with, respectively, NCC (p = 0.030; r² = 0.34), and NCC (p = 0.0094; r² = 0.63) + PY (p = 0.0078; r² = 0.64).

CONCLUSIONS

This pilot study established a quantitative extraction method for nicotine and cotinine from human gingival samples. Additionally, FTND was associated with gingival cotinine. However, further large-scale studies are needed to confirm the relationship between nicotine dependence and gingival intoxication.

Critical role of peripheral sensory systems in mediating the neural effects of nicotine following its acute and repeated exposure

It is well established that the reinforcing properties of nicotine (NIC) depend on its action on nicotinic acetylcholine receptors expressed by brain neurons. However, when administered systemically, NIC first phasically activates nicotinic receptors located on the afferents of sensory nerves at the sites of drug administration before reaching the brain and directly interacting with central neurons. While this peripheral action of NIC has been known for years, it is usually neglected in any consideration of the drug's reinforcing properties and experience-dependent changes of its behavioral and physiological effects. The goal of this work was to review our recent behavioral, electrophysiological, and physiological data suggesting the critical importance of peripheral actions of NIC in mediating its neural effects following acute drug exposure and their involvement in alterations of NIC effects consistently occurring following repeated drug exposure. Because NIC, by acting peripherally, produces a rapid sensory signal to the central nervous system that is followed by slower, more prolonged direct drug actions in the brain, these two pharmacological actions interact in the central nervous system during repeated drug use with the development of Pavlovian conditioned association. This within-drug conditioning mechanism could explain the experience-dependent changes in the physiological, behavioral, and human psychoemotional effects of NIC, which, in drug-experienced individuals, always represent a combination of pharmacological and learning variables.

Rapid sensitization of physiological, neuronal, and locomotor effects of nicotine: critical role of peripheral drug actions

Repeated exposure to nicotine and other psychostimulant drugs produces persistent increases in their psychomotor and physiological effects (sensitization), a phenomenon related to the drugs' reinforcing properties and abuse potential. Here we examined the role of peripheral actions of nicotine in nicotine-induced sensitization of centrally mediated physiological parameters (brain, muscle, and skin temperatures), cortical and VTA EEG, neck EMG activity, and locomotion in freely moving rats. Repeated injections of intravenous nicotine (30 μg/kg) induced sensitization of the drug's effects on all these measures. In contrast, repeated injections of the peripherally acting analog of nicotine, nicotine pyrrolidine methiodide (nicotine(PM), 30 μg/kg, i.v.) resulted in habituation (tolerance) of the same physiological, neuronal, and behavioral measures. However, after repeated nicotine exposure, acute nicotine(PM) injections induced nicotine-like physiological responses: powerful cortical and VTA EEG desynchronization, EMG activation, a large brain temperature increase, but weaker hyperlocomotion. Additionally, both the acute locomotor response to nicotine and nicotine-induced locomotor sensitization were attenuated by blockade of peripheral nicotinic receptors by hexamethonium (3 mg/kg, i.v.). These data suggest that the peripheral actions of nicotine, which precede its direct central actions, serve as a conditioned interoceptive cue capable of eliciting nicotine-like physiological and neural responses after repeated nicotine exposure. Thus, by providing a neural signal to the CNS that is repeatedly paired with the direct central effects of nicotine, the drug's peripheral actions play a critical role in the development of nicotine-induced physiological, neural, and behavioral sensitization.

Application of nicotine enantiomers, derivatives and analogues in therapy of neurodegenerative disorders

This review gives a brief overview over the major aspects of application of the nicotine alkaloid and its close derivatives in the therapy of some neurodegenerative disorders and diseases (e.g. Alzheimer's disease, Parkinson's disease, Tourette's syndrome, schizophrenia etc.). The issues concerning methods of nicotine analysis and isolation, and some molecular aspects of nicotine pharmacology are included. The natural and synthetic analogues of nicotine that are considered for medical practice are also mentioned. The molecular properties of two naturally occurring nicotine enantiomers are compared--the less-common but less-toxic (R)-nicotine is suggested as a natural compound that may find its place in pharmaceutical practice.

Brain uptake of nonsteroidal anti-inflammatory drugs: ibuprofen, flurbiprofen, and indomethacin

PURPOSE

To determine the roles of blood-brain barrier (BBB) transport and plasma protein binding in brain uptake of nonsteroidal anti-inflammatory drugs (NSAIDs)-ibuprofen, flurbiprofen, and indomethacin.

METHODS

Brain uptake was measured using in situ rat brain perfusion technique.

RESULTS

[14C]Ibuprofen, [3H]flurbiprofen, and [14C]indomethacin were rapidly taken up into the brain in the absence of plasma protein with BBB permeability-surface area products (PS(u)) to free drug of (2.63 +/- 0.11) x 10(-2), (1.60 +/- 0.08) x 10(-2), and (0.64 +/- 0.05) x 10(-2) mL s(-1) g(-1) (n = 9-11), respectively. BBB [14C]ibuprofen uptake was inhibited by unlabeled ibuprofen (Km = 0.85 +/- 0.02 mM, Vmax = 13.5 +/- 0.4 nmol s(-1) g(-1)) and indomethacin, but not by pyruvate, probenecid, digoxin, or valproate. No evidence was found for saturable BBB uptake of [3H]flurbiprofen or [14C]indomethacin. Initial brain uptake for all three NSAIDs was reduced by the addition of albumin to the perfusion buffer. The magnitude of the brain uptake reduction correlated with the NSAID free fraction in the perfusate.

CONCLUSIONS

Free ibuprofen, flurbiprofen, and indomethacin rapidly cross the BBB, with ibuprofen exhibiting a saturable component of transport. Plasma protein binding limits brain NSAID uptake by reducing the free fraction of NSAID in the circulation.