Local and global calcium signals associated with the opening of neuronal alpha7 nicotinic acetylcholine receptors

Growth and neurite stimulating effects of the neonicotinoid pesticide clothianidin on human neuroblastoma SH-SY5Y cells

Neonicotinoids are one of most widely used pesticides targeting nicotinic acetylcholine receptors (nAChRs) of insects. Recent epidemiological evidence revealed increasing amounts of neonicotinoids detected in human samples, raising the critical question of whether neonicotinoids affect human health. We investigated the effects of a neonicotinoid pesticide clothianidin (CTD) on human neuroblastoma SH-SY5Y cells as in vitro models of human neuronal cells. Cellular and functional effects of micromolar doses of CTD were evaluated by changes in cell growth, intracellular signaling activities and gene expression profiles. We examined further the effects of CTD on neuronal differentiation by measuring neurite outgrowth. Exposure to CTD (1-100 μM) significantly increased the number of cells within 24 h of culture. The nAChRs antagonists, mecamylamine and SR16584, inhibited this effect, suggesting human α3β4 nAChRs could be targets of neonicotinoids. We observed a transient intracellular calcium influx and increased phosphorylation of extracellular signal-regulated kinase 1/2 shortly after exposure to CTD. Transcriptome analysis revealed that CTD down-regulated genes involved in neuronal function (e.g., formation of filopodia and calcium ion influx) and morphology (e.g., axon guidance signaling and cytoskeleton signaling); these changes were reflected by a finding of increased neurite length during neuronal differentiation. These findings provide novel insight into the potential risks of neonicotinoids to the human nervous system.

New Insights on Neuronal Nicotinic Acetylcholine Receptors as Targets for Pain and Inflammation: A Focus on α7 nAChRs

BACKGROUND

Nicotine and nicotinic acetylcholine receptors (nAChRs) have been explored for the past three decades as targets for pain control. The aim of this review is to introduce readers particularly to α7 nAChRs in a perspective of pain and its modulation.

METHODS

Developments for α7 nAChR modulators and recent animal studies related to pain are reviewed.

RESULTS

Accumulating evidences suggest that selective ligands for α7 nAChRs hold promise in the treatment of chronic pain conditions as they lack many of side effects associated with other nicotinic receptor types.

CONCLUSION

This review provides the reader recent insights on α7 nAChRs from structure and function to the latest findings on the pharmacology and therapeutic targeting of these receptors for the treatment of pain and inflammation.

Differential Effects of Quercetin and Quercetin Glycosides on Human α7 Nicotinic Acetylcholine Receptor-Mediated Ion Currents

Quercetin is a flavonoid usually found in fruits and vegetables. Aside from its antioxidative effects, quercetin, like other flavonoids, has a various neuropharmacological actions. Quercetin-3-O-rhamnoside (Rham1), quercetin-3-O-rutinoside (Rutin), and quercetin-3-(2(G)-rhamnosylrutinoside (Rham2) are mono-, di-, and tri-glycosylated forms of quercetin, respectively. In a previous study, we showed that quercetin can enhance α7 nicotinic acetylcholine receptor (α7 nAChR)-mediated ion currents. However, the role of the carbohydrates attached to quercetin in the regulation of α7 nAChR channel activity has not been determined. In the present study, we investigated the effects of quercetin glycosides on the acetylcholine induced peak inward current (I_ACh) in Xenopus oocytes expressing the α7 nAChR. I_ACh was measured with a two-electrode voltage clamp technique. In oocytes injected with α7 nAChR copy RNA, quercetin enhanced I_ACh, whereas quercetin glycosides inhibited I_ACh. Quercetin glycosides mediated an inhibition of I_ACh, which increased when they were pre-applied and the inhibitory effects were concentration dependent. The order of I_ACh inhibition by quercetin glycosides was Rutin≥Rham1>Rham2. Quercetin glycosides-mediated I_ACh enhancement was not affected by ACh concentration and appeared voltage-independent. Furthermore, quercetin-mediated I_ACh inhibition can be attenuated when quercetin is co-applied with Rham1 and Rutin, indicating that quercetin glycosides could interfere with quercetin-mediated α7 nAChR regulation and that the number of carbohydrates in the quercetin glycoside plays a key role in the interruption of quercetin action. These results show that quercetin and quercetin glycosides regulate the α7 nAChR in a differential manner.

The Role of nAChR and Calcium Signaling in Pancreatic Cancer Initiation and Progression

Pancreatic cancer shows a strong correlation with smoking and the current therapeutic strategies have been relatively ineffective in improving the survival of patients. Efforts have been made over the past many years to understand the molecular events that drive the initiation and progression of pancreatic cancer, especially in the context of smoking. It has become clear that components of tobacco smoke not only initiate these cancers, especially pancreatic ductal adenocarcinomas (PDACs) through their mutagenic properties, but can also promote the growth and metastasis of these tumors by stimulating cell proliferation, angiogenesis, invasion and epithelial-mesenchymal transition. Studies in cell culture systems, animal models and human samples have shown that nicotinic acetylcholine receptor (nAChR) activation enhances these tumor-promoting events by channeling signaling through multiple pathways. In this context, signaling through calcium channels appear to facilitate pancreatic cancer growth by itself or downstream of nAChRs. This review article highlights the role of nAChR downstream signaling events and calcium signaling in the growth, metastasis as well as drug resistance of pancreatic cancer.

The effect of α7 nicotinic receptor activation on glutamatergic transmission in the hippocampus

Nicotinic acetylcholine receptors (nAChRs) are expressed widely in the CNS, and mediate both synaptic and perisynaptic activities of endogenous cholinergic inputs and pharmacological actions of exogenous compounds (e.g., nicotine and choline). Behavioral studies indicate that nicotine improves such cognitive functions as learning and memory, however the cellular mechanism of these actions remains elusive. With help from newly developed biosensors and optogenetic tools, recent studies provide new insights on signaling mechanisms involved in the activation of nAChRs. Here we will review α7 nAChR's action in the tri-synaptic pathway in the hippocampus. The effects of α7 nAChR activation via either exogenous compounds or endogenous cholinergic innervation are detailed for spontaneous and evoked glutamatergic synaptic transmission and synaptic plasticity, as well as the underlying signaling mechanisms. In summary, α7 nAChRs trigger intracellular calcium rise and calcium-dependent signaling pathways to enhance glutamate release and induce glutamatergic synaptic plasticity.

Activation of the Macrophage α7 Nicotinic Acetylcholine Receptor and Control of Inflammation

Inflammatory responses to stimuli are essential body defenses against foreign threats. However, uncontrolled inflammation may result in serious health problems, which can be life-threatening. The α7 nicotinic acetylcholine receptor, a ligand-gated ion channel expressed in the nervous and immune systems, has an essential role in the control of inflammation. Activation of the macrophage α7 receptor by acetylcholine, nicotine, or other agonists, selectively inhibits production of pro-inflammatory cytokines while leaving anti-inflammatory cytokines undisturbed. The neural control of this regulation pathway was discovered recently and it was named the cholinergic anti-inflammatory pathway (CAP). When afferent vagus nerve terminals are activated by cytokines or other pro-inflammatory stimuli, the message travels through the afferent vagus nerve, resulting in action potentials traveling down efferent vagus nerve fibers in a process that eventually leads to macrophage α7 activation by acetylcholine and inhibition of pro-inflammatory cytokines production. The mechanism by which activation of α7 in macrophages regulates pro-inflammatory responses is subject of intense research, and important insights have thus been made. The results suggest that activation of the macrophage α7 controls inflammation by inhibiting NF-κB nuclear translocation, and activating the JAK2/STAT3 pathway among other suggested pathways. While the α7 is well characterized as a ligand-gated ion channel in neurons, whole-cell patch clamp experiments suggest that α7's ion channel activity, defined as the translocation of ions across the membrane in response to ligands, is absent in leukocytes, and therefore, ion channel activity is generally assumed not to be required for the operation of the CAP. In this perspective, we briefly review macrophage α7 activation as it relates to the control of inflammation, and broaden the current view by providing single-channel currents as evidence that the α7 expressed in macrophages retains its ion translocation activity despite the absence of whole-cell currents. Whether this ion-translocating activity is relevant for the proper operation of the CAP or other important physiological processes remains obscure.

Positive allosteric modulation of alpha-7 nicotinic receptors promotes cell death by inducing Ca(2+) release from the endoplasmic reticulum

Positive allosteric modulation of α7 isoform of nicotinic acetylcholine receptors (α7-nAChRs) is emerging as a promising therapeutic approach for central nervous system disorders such as schizophrenia or Alzheimer's disease. However, its effect on Ca(2+) signaling and cell viability remains controversial. This study focuses on how the type II positive allosteric modulator (PAM II) PNU120596 affects intracellular Ca(2+) signaling and cell viability. We used human SH-SY5Y neuroblastoma cells overexpressing α7-nAChRs (α7-SH) and their control (C-SH). We monitored cytoplasmic and endoplasmic reticulum (ER) Ca(2+) with Fura-2 and the genetically encoded cameleon targeting the ER, respectively. Nicotinic inward currents were measured using patch-clamp techniques. Viability was assessed using methylthiazolyl blue tetrazolium bromide or propidium iodide staining. We observed that in the presence of a nicotinic agonist, PNU120596 (i) reduced viability of α7-SH but not of C-SH cells; (ii) significantly increased inward nicotinic currents and cytosolic Ca(2+) concentration; (iii) released Ca(2+) from the ER by a Ca(2+) -induced Ca(2+) release mechanism only in α7-SH cells; (iv) was cytotoxic in rat organotypic hippocampal slice cultures; and, lastly, all these effects were prevented by selective blockade of α7-nAChRs, ryanodine receptors, or IP3 receptors. In conclusion, positive allosteric modulation of α7-nAChRs with the PAM II PNU120596 can lead to dysregulation of ER Ca(2+) , overloading of intracellular Ca(2+) , and neuronal cell death. This study focuses on how the type II positive allosteric modulator PNU120596 (PAM II PNU12) affects intracellular Ca(2+) signaling and cell viability. Using SH-SY5Y neuroblastoma cells overexpressing α7-nAChRs (α7-SH) and their control (C-SH), we find that PAM of α7-nAChRs with PNU120596: (i) increases inward calcium current (ICa ) and cytosolic Ca(2+) concentration ([Ca(2+) ]cyt ); (ii) releases Ca(2+) from the ER ([Ca(2+) ]ER ) by a Ca(2+) -induced Ca(2+) release mechanism; and (iv) reduces cell viability. These findings were corroborated in rat hippocampal organotypic cultures. [Ca(2+) ]cyt , cytosolic Ca(2+) concentration; [Ca(2+) ]ER , endoplasmic reticulum Ca(2+) concentration; α7 nAChR, α7 isoform of nicotinic acetylcholine receptors; α7-SH, SH-SY5Y stably overexpressing α7 nAChRs cells; C-SH, control SH-SY5Y cells; Nic, nicotine; PNU12, PNU120596.

Merging old and new perspectives on nicotinic acetylcholine receptors

This review covers history underlying the discovery of the molecular mediators of nicotine's effects in the brain and the diversity of the nicotinic acetylcholine receptor (nAChR) subtypes. Models are presented for both their structure and their function as mediators of signal transduction, with special consideration of the differences between the two main subtypes: heteromeric receptors, which are specialized for rapid electrochemical signal transduction, and homomeric α7 receptors, which have come to be implicated in both ionotropic and metabotropic signaling. This review presents perspectives on the pharmacology and therapeutic targeting of nAChRs for the treatment of nicotine dependence or disease.

Presynaptic α7 nicotinic acetylcholine receptors enhance hippocampal mossy fiber glutamatergic transmission via PKA activation

Nicotinic acetylcholine receptors (nAChRs) are expressed widely in the CNS, and mediate both synaptic and perisynaptic activities of endogenous cholinergic inputs and pharmacological actions of exogenous compounds (e.g., nicotine and choline). Behavioral studies indicate that nicotine improves such cognitive functions as learning and memory. However, the mechanism of nicotine's action on cognitive function remains elusive. We performed patch-clamp recordings from hippocampal CA3 pyramidal neurons to determine the effect of nicotine on mossy fiber glutamatergic synaptic transmission. We found that nicotine in combination with NS1738, an α7 nAChR-positive allosteric modulator, strongly potentiated the amplitude of evoked EPSCs (eEPSCs), and reduced the EPSC paired-pulse ratio. The action of nicotine and NS1738 was mimicked by PNU-282987 (an α7 nAChR agonist), and was absent in α7 nAChR knock-out mice. These data indicate that activation of α7 nAChRs was both necessary and sufficient to enhance the amplitude of eEPSCs. BAPTA applied postsynaptically failed to block the action of nicotine and NS1738, suggesting again a presynaptic action of the α7 nAChRs. We also observed α7 nAChR-mediated calcium rises at mossy fiber giant terminals, indicating the presence of functional α7 nAChRs at presynaptic terminals. Furthermore, the addition of PNU-282987 enhanced action potential-dependent calcium transient at these terminals. Last, the potentiating effect of PNU-282987 on eEPSCs was abolished by inhibition of protein kinase A (PKA). Our findings indicate that activation of α7 nAChRs at presynaptic sites, via a mechanism involving PKA, plays a critical role in enhancing synaptic efficiency of hippocampal mossy fiber transmission.

Nicotine elicits prolonged calcium signaling along ventral hippocampal axons

Presynaptic nicotinic acetylcholine receptors (nAChRs) have long been implicated in the modulation of CNS circuits. We previously reported that brief exposure to low concentrations of nicotine induced sustained potentiation of glutamatergic transmission at ventral hippocampal (vHipp)-striatal synapses. Here, we exploited nAChR subtype-selective antagonists and agonists and α7*nAChR knockout mutant mice (α7-/-) to elucidate the signaling mechanisms underlying nAChR-mediated modulation of synaptic transmission. Using a combination of micro-slices culture from WT and α7-/-mice, calcium imaging, and immuno-histochemical techniques, we found that nicotine elicits localized and oscillatory increases in intracellular Ca(2+) along vHipp axons that persists for up to 30 minutes. The sustained phase of the nicotine-induced Ca(2+) response was blocked by α-BgTx but not by DHβE and was mimicked by α7*nAChR agonists but not by non-α7*nAChR agonists. In vHipp slices from α7-/- mice, nicotine elicited only transient increases of axonal Ca(2+) signals and did not activate CaMKII. The sustained phase of the nicotine-induced Ca(2+) response required localized activation of CaMKII, phospholipase C, and IP3 receptor mediated Ca(2+)-induced Ca(2+) release (CICR). In conclusion, activation of presynaptic nAChRs by nicotine elicits Ca(2+) influx into the presynaptic axons, the sustained phase of the nicotine-induced Ca(2+) response requires that axonal α7*nAChR activate a downstream signaling network in the vHipp axons.

Nicotine prevents synaptic impairment induced by amyloid-β oligomers through α7-nicotinic acetylcholine receptor activation

An emerging view on Alzheimer disease's (AD) pathogenesis considers amyloid-β (Aβ) oligomers as a key factor in synaptic impairment and rodent spatial memory decline. Alterations in the α7-nicotinic acetylcholine receptor (α7-nAChR) have been implicated in AD pathology. Herein, we report that nicotine, an unselective α7-nAChR agonist, protects from morphological and synaptic impairments induced by Aβ oligomers. Interestingly, nicotine prevents both early postsynaptic impairment and late presynaptic damage induced by Aβ oligomers through the α7-nAChR/phosphatidylinositol-3-kinase (PI3K) signaling pathway. On the other hand, a cross-talk between α7-nAChR and the Wnt/β-catenin signaling pathway was revealed by the following facts: (1) nicotine stabilizes β-catenin, in a concentration-dependent manner; (2) nicotine prevents Aβ-induced loss of β-catenin through the α7-nAChR; and (3) activation of canonical Wnt/β-catenin signaling induces α7-nAChR expression. Analysis of the α7-nAChR promoter indicates that this receptor is a new Wnt target gene. Taken together, these results demonstrate that nicotine prevents memory deficits and synaptic impairment induced by Aβ oligomers. In addition, nicotine improves memory in young APP/PS1 transgenic mice before extensive amyloid deposition and senile plaque development, and also in old mice where senile plaques have already formed. Activation of the α7-nAChR/PI3K signaling pathway and its cross-talk with the Wnt signaling pathway might well be therapeutic targets for potential AD treatments.

α7 nicotinic ACh receptors as a ligand-gated source of Ca(2+) ions: the search for a Ca(2+) optimum

The spatiotemporal distribution of cytosolic Ca(2+) ions is a key determinant of neuronal behavior and survival. Distinct sources of Ca(2+) ions including ligand- and voltage-gated Ca(2+) channels contribute to intracellular Ca(2+) homeostasis. Many normal physiological and therapeutic neuronal functions are Ca(2+)-dependent, however an excess of cytosolic Ca(2+) or a lack of the appropriate balance between Ca(2+) entry and clearance may destroy cellular integrity and cause cellular death. Therefore, the existence of optimal spatiotemporal patterns of cytosolic Ca(2+) elevations and thus, optimal activation of ligand- and voltage-gated Ca(2+) ion channels are postulated to benefit neuronal function and survival. Alpha7 nicotinic -acetylcholine receptors (nAChRs) are highly permeable to Ca(2+) ions and play an important role in modulation of neurotransmitter release, gene expression and neuroprotection in a variety of neuronal and non-neuronal cells. In this review, the focus is placed on α7 nAChR-mediated currents and Ca(2+) influx and how this source of Ca(2+) entry compares to NMDA receptors in supporting cytosolic Ca(2+) homeostasis, neuronal function and survival.

Central nicotinic acetylcholine receptor involved in Ca(2+) -calmodulin-endothelial nitric oxide synthase pathway modulated hypotensive effects

BACKGROUND AND PURPOSE

Recent evidence has suggested that nicotine decreases blood pressure (BP) and heart rate (HR) in the nucleus tractus solitarii (NTS), indicating that nicotinic acetylcholine receptors (nAChRs) play an important role in BP control in the NTS. However, the signalling mechanisms involved in nAChR-mediated depressor effects in the NTS are unclear. Hence, the aim of this study was to investigate these signalling mechanisms.

EXPERIMENTAL APPROACH

Depressor responses to nicotine microinjected into the NTS of Wistar-Kyoto rats were elicited in the absence and presence of an antagonist of α7 nAChR, the calcium chelator ethylene glycol tetraacetic acid, a calmodulin-specific inhibitor, nitric oxide (NO) synthase (NOS) inhibitor, endothelial NOS (eNOS)-selective inhibitor or neuronal NOS (nNOS)-specific inhibitor.

KEY RESULTS

Microinjection of nicotine into the NTS produced a dose-dependent decrease in BP and HR, and increased nitrate levels. This depressor effect of nicotine was attenuated after pretreatment with a nAChR antagonist or blockers of the calmodulin-eNOS pathway. In contrast, N5-(1-Imino-3-butenyl)-L-ornithine (vinyl-L-NIO), nNOS-specific inhibitor, did not diminish these nicotine-mediated effects. Calmodulin was found to bind eNOS after nicotine injection into NTS. However, nicotine did not affect the eNOS phosphorylation level or eNOS upstream extracellular signal-regulated kinases (ERK)1/2 and Akt phosphorylation levels. Furthermore, pretreatment with an ERK1/2 or Akt inhibitor did not attenuate nicotine-induced depressor effects in the NTS.

CONCLUSIONS AND IMPLICATIONS

These results suggest that the nAChR-Ca(2+) -calmodulin-eNOS-NO signalling pathway, but not nNOS, plays a significant role in central BP regulation, and neither the ERK1/2 nor Akt signalling pathway are significantly involved in the activation of eNOS by nAChRs in the NTS.

Quercetin enhances human α7 nicotinic acetylcholine receptor-mediated ion current through interactions with Ca(2+) binding sites

The flavonoid quercetin is a low molecular weight substance found in fruits and vegetables. Aside from its anti-oxidative effect, quercetin, like other flavonoids, has a wide range of neuropharmacological actions. The α7 nicotinic acetylcholine receptor (α7 nAChR) has a Ca(2+)-binding site, is highly permeable to the Ca(2+) ion, and plays important roles in Ca(2+)-related normal brain functions. Dysfunctions of α7 nAChR are associated with a variety of neurological disorders. In the present study, we investigated the effects of quercetin on the ACh-induced inward peak current (I(ACh)) in Xenopus oocytes that heterologously express human α7 nAChR. I(ACh) was measured with the two-electrode voltage clamp technique. In oocytes injected with α7 nAChR cRNA, the effects of the co-application of quercetin on I(ACh) were concentration-dependent and reversible. The ED(50) was 36.1 + 6.1 μM. Quercetin-mediated enhancement of I(ACh) caused more potentiation when quercetin was pre-applied. The degree of I(ACh) potentiation by quercetin pre-application was time-dependent and saturated after 1 min. Quercetin-mediated I(ACh) enhancement was not affected by ACh concentration and was voltage-independent. However, quercetin-mediated I(ACh) enhancement was dependent on extracellular Ca(2+) concentrations and was specific to the Ca(2+) ion, since the removal of extracellular Ca(2+) or the addition of Ba(2+) instead of Ca(2+) greatly diminished quercetin enhancement of I(ACh). The mutation of Glu195 to Gln195, in the Ca(2+)-binding site, almost completely diminished quercetin-mediated I(ACh) enhancement. These results indicate that quercetin-mediated I(ACh) enhancement human α7 nAChR heterologously expressed in Xenopus oocytes could be achieved through interactions with the Ca(2+)-binding site of the receptor.

Prefrontal beta2 subunit-containing and alpha7 nicotinic acetylcholine receptors differentially control glutamatergic and cholinergic signaling

One-second-long increases in prefrontal cholinergic activity ("transients") were demonstrated previously to be necessary for the incorporation of cues into ongoing cognitive processes ("cue detection"). Nicotine and, more robustly, selective agonists at alpha4beta2* nicotinic acetylcholine receptors (nAChRs) enhance cue detection and attentional performance by augmenting prefrontal cholinergic activity. The present experiments determined the role of beta2-containing and alpha7 nAChRs in the generation of prefrontal cholinergic and glutamatergic transients in vivo. Transients were evoked by nicotine, the alpha4beta2* nAChR agonist ABT-089 [2-methyl-3-(2-(S)-pyrrolindinylmethoxy) pyridine dihydrochloride], or the alpha7 nAChR agonist A-582941 [2-methyl-5-(6-phenyl-pyridazin-3-yl)-octahydro-pyrrolo[3,4-c]pyrrole]. Transients were recorded in mice lacking beta2 or alpha7 nAChRs and in rats after removal of thalamic glutamatergic or midbrain dopaminergic inputs to prefrontal cortex. The main results indicate that stimulation of alpha4beta2* nAChRs evokes glutamate release and that the presence of thalamic afferents is necessary for the generation of cholinergic transients. ABT-089-evoked transients were completely abolished in mice lacking beta2* nAChRs. The amplitude, but not the decay rate, of nicotine-evoked transients was reduced by beta2* knock-out. Conversely, in mice lacking the alpha7 nAChR, the decay rate, but not the amplitude, of nicotine-evoked cholinergic and glutamatergic transients was attenuated. Substantiating the role of alpha7 nAChR in controlling the duration of release events, stimulation of alpha7 nAChR produced cholinergic transients that lasted 10- to 15-fold longer than those evoked by nicotine. alpha7 nAChR-evoked cholinergic transients are mediated in part by dopaminergic activity. Prefrontal alpha4beta2* nAChRs play a key role in evoking and facilitating the transient glutamatergic-cholinergic interactions that are necessary for cue detection and attentional performance.

alpha7-Nicotinic receptor antagonists at the beginning of a clinical era for NSCLC and Mesothelioma?

Of the human solid cancers, Non-Small Cell Lung Cancer (NSCLC) and Malignant Pleural Mesothelioma (MPM) display a natural history supporting the concept that they develop from multiple preneoplastic pathways. Recently, new evidence suggested that nicotinic Acetylcholine Receptors (nAChRs) play a significant role in lung cancer predisposition and natural history. This review is based on some translational research aimed at evaluating the potential therapeutic effect of nAChR antagonists on NSCLC and MPM. The background and rationale of this approach are based on the experimental observations that: (a) NSCLC and MPM cells express nAChRs and (b) the activation of these receptors by agonists, namely nicotine, inhibits apoptosis, whereas receptor antagonists have a pro-apoptotic effect.

Nicotine: a pro-angiogenic factor

Angiogenesis, the formation of new blood vessels from pre-existing ones, is regulated by the balance between angiogenic activating and inhibiting factors. Recent evidence indicates that nicotine, an alkaloid compound, presents pro-angiogenic effects in certain concentrations. Nicotine-induced angiogenesis results from the stimulation of non-neuronal nicotinic acetylcholinergic receptors (particularly alpha 7-NAChR subtype) and involves growth factor secretion and activation of intracellular signalling pathways. Although nicotine is a constituent of tobacco smoke, its contribution towards pathophysiology of several tobacco-associated pathologies is controversial. Nowadays, nicotine is used in tobacco smoke cessation programs, but, again, its use is still a matter of discordance regarding cardiovascular morbidity. Nevertheless, given the established effects of nicotine-induced angiogenesis, this alkaloid might be of therapeutic value in situations of inefficient angiogenesis, such as peripheral vascular impairment and tissue ischemia. Conversely, blockade of nicotine pathway can be helpful in complications exhibiting excessive angiogenesis, namely in diabetic retinopathy and nephropathy or neoplasia. Knowing that nicotine is involved in many angiogenic-associated disorders with a high prevalence in the western world, and that this alkaloid widely used in smoke cessation programs, elucidation of the action of nicotine on the vascularization process is of utmost importance. The current paper provides an overview of the effects of nicotine in angiogenesis.