Ashbeel Roy

Regulation of cholinergic activity by the vesicular acetylcholine transporter.

Acetylcholine, the first chemical to be identified as a neurotransmitter, is packed in synaptic vesicles by the activity of VAChT (vesicular acetylcholine transporter). A decrease in VAChT expression has been reported in a number of diseases, and this has consequences for the amount of acetylcholine loaded in synaptic vesicles as well as for neurotransmitter release. Several genetically modified mice targeting the VAChT gene have been generated, providing novel models to understand how changes in VAChT affect transmitter release. A surprising finding is that most cholinergic neurons in the brain also can express a second type of vesicular neurotransmitter transporter that allows these neurons to secrete two distinct neurotransmitters. Thus a given neuron can use two neurotransmitters to regulate different physiological functions. In addition, recent data indicate that non-neuronal cells can also express the machinery used to synthesize and release acetylcholine. Some of these cells rely on VAChT to secrete acetylcholine with potential physiological consequences in the periphery. Hence novel functions for the oldest neurotransmitter known are emerging with the potential to provide new targets for the treatment of several pathological conditions.

Cardiomyocyte-secreted acetylcholine is required for maintenance of homeostasis in the heart

Heart activity and long‐term function are regulated by the sympathetic and parasympathetic branches of the nervous system. Parasympathetic neurons have received increased attention recently because acetylcholine (ACh) has been shown to play protective roles in heart disease. However, parasympathetic innervation is sparse in the heart, raising the question of how cholinergic signaling regulates cardiomyocytes. We hypothesized that non‐neuronal secretion of ACh from cardiomyocytes plays a role in cholinergic regulation of cardiac activity. To test this possibility, we eliminated secretion of ACh exclusively from cardiomyocytes by targeting the vesicular acetylcholine transporter (VAChT). We find that lack of cardiomyocyte‐secreted ACh disturbs the regulation of cardiac activity and causes cardiomyocyte remodeling. Mutant mice present normal hemodynamic parameters under nonstressful conditions; however, following exercise, their heart rate response is increased. Moreover, hearts from mutant mice present increased oxidative stress, altered calcium signaling, remodeling, and hypertrophy. Hence, without cardiomyocyte‐derived ACh secretion, hearts from mutant mice show signs of imbalanced autonomic activity consistent with decreased cholinergic drive. These unexpected results suggest that cardiomyocyte‐derived ACh is required for maintenance of cardiac homeostasis and regulates critical signaling pathways necessary to maintain normal heart activity. We propose that this non‐neuronal source of ACh boosts parasympathetic cholinergic signaling to counterbalance sympathetic activity regulating multiple aspects of heart physiology.—Roy, A., Fields, W. C., Rocha‐Resende, C., Resende, R. R., Guatimosim, S., Prado, V. F., Gros, R., Prado, M. A. M., Cardiomyocyte‐secreted acetylcholine is required for maintenance of homeostasis in the heart. FASEB J. 27, 5072–5082 (2013). www.fasebj.org

Non-neuronal cholinergic machinery present in cardiomyocytes offsets hypertrophic signals

Recent work has provided compelling evidence that increased levels of acetylcholine (ACh) can be protective in heart failure, whereas reduced levels of ACh secretion can cause heart malfunction. Previous data show that cardiomyocytes themselves can actively secrete ACh, raising the question of whether this cardiomyocyte derived ACh may contribute to the protective effects of ACh in the heart. To address the functionality of this non-neuronal ACh machinery, we used cholinesterase inhibitors and a siRNA targeted to AChE (acetylcholinesterase) as a way to increase the availability of ACh secreted by cardiac cells. By using nitric oxide (NO) formation as a biological sensor for released ACh, we showed that cholinesterase inhibition increased NO levels in freshly isolated ventricular myocytes and that this effect was prevented by atropine, a muscarinic receptor antagonist, and by inhibition of ACh synthesis or vesicular storage. Functionally, cholinesterase inhibition prevented the hypertrophic effect as well as molecular changes and calcium transient alterations induced by adrenergic overstimulation in cardiomyocytes. Moreover, inhibition of ACh storage or atropine blunted the anti-hypertrophic action of cholinesterase inhibition. Altogether, our results show that cardiomyocytes possess functional cholinergic machinery that offsets deleterious effects of hyperadrenergic stimulation. In addition, we show that adrenergic stimulation upregulates expression levels of cholinergic components. We propose that this cardiomyocyte cholinergic signaling could amplify the protective effects of the parasympathetic nervous system in the heart and may counteract or partially neutralize hypertrophic adrenergic effects.

Cholinergic activity as a new target in diseases of the heart.

The autonomic nervous system is an important modulator of cardiac signaling in both health and disease. In fact, the significance of altered parasympathetic tone in cardiac disease has recently come to the forefront. Both neuronal and nonneuronal cholinergic signaling likely play a physiological role, since modulating acetylcholine (ACh) signaling from neurons or cardiomyocytes appears to have significant consequences in both health and disease. Notably, many of these effects are solely due to changes in cholinergic signaling, without altered sympathetic drive, which is known to have significant adverse effects in disease states. As such, it is likely that enhanced ACh-mediated signaling not only has direct positive effects on cardiomyocytes, but it also offsets the negative effects of hyperadrenergic tone. In this review, we discuss recent studies that implicate ACh as a major regulator of cardiac remodeling and provide support for the notion that enhancing cholinergic signaling in human patients with cardiac disease can reduce morbidity and mortality. These recent results support the idea of developing large clinical trials of strategies to increase cholinergic tone, either by stimulating the vagus or by increased availability of Ach, in heart failure.

DNMT3B (C46359T) Polymorphisms and Immunoexpression of DNMT3b and DNMT1 Proteins in Oral Lichen Planus

Objective: To investigate the DNMT3B (C46359T) polymorphism and immunoexpression of DNMT3b and DNMT1 in oral lichen planus (OLP) compared to a control group. Methods: We aimed to investigate the DNMT3B (C46359T) polymorphism and immunoexpression of DNMT3b and DNMT1 in OLP (n = 32), comparing it with oral mucosa (control; n = 24). The DNMT3B (C46359T) polymorphism was analyzed using the RFLP-PCR and DNMT1, and DNMT3a proteins were identified using immunohistochemistry. We also compared the DNMT3B expression in OLP and oral inflammatory fibrous hyperplasia (OIFH), another oral inflammatory disease. Differences between the groups were determined by specific statistical analyses. Results: The CT genotype of DNMT3B was associated with OLP development (p = 0.012). Increased expression of DNMT3B and DNMT1 was observed in OLP compared to the control group (p = 0.014 and p = 0.001, respectively). A significant increase in DNMT3B protein levels was observed in the genotype CT in DNMT3B (C46359T) polymorphisms (p = 0.045). No DNMT3B expression differences between OLP and OIFH were observed. Conclusions: Our data show that the DNMT3B (C46359T) polymorphism is associated with OLP development. Furthermore, increased expression of the enzyme DNMT3B, an epigenetic-associated protein, is present in OLP.

Increased VEGFR2 and MMP9 protein levels are associated with epithelial dysplasia grading

The present study aimed to compare levels of VEGFR2 and MMP-9 among control, epithelial dysplasia (ED) and oral squamous cell carcinoma (OSCC) groups. We analyzed 48 patients with oral leukoplakia (OL), 20 patients with OSCC and 21 patients without OL and OSCC. Immunohistochemistry of VEGFR2 and MMP9 were performed and compared among groups. Analysis of tissue immunolocalization of VEGFR2 and MMP-9 assumed non-parametrical distribution and comparison between groups was performed using the Mann-Whitney and Kruskal-Wallis statistical tests. VEGFR2 and MMP9 immunoexpression appeared to correlate with the degree of dysplasia and was observed to increase in lesions with more severe dysplasia as compared to those with lower degrees of dysplasia. Immunoreactivity of MMP-9 was lower in the OL samples compared to the OSCC samples (p = 0.004). We observed no difference in VEGFR2 protein levels between OL and OSCC samples. A positive correlation was found between VEGFR2 and MMP-9 in OL samples (r = +0.452, p = 0.001), however, no correlation was found in OSCC samples (r = -0.042, p = 0.861). In conclusion, the results of the current study suggest that expression of MMP9 and VEGFR2 is associated with ED grading and MMP9 levels are increased in OSCC.

Cardiac acetylcholine inhibits ventricular remodeling and dysfunction under pathologic conditions.

Autonomic dysfunction is a characteristic of cardiac disease and decreased vagal activity is observed in heart failure. Rodent cardiomyocytes produce de novo ACh, which is critical in maintaining cardiac homeostasis. We report that this nonneuronal cholinergic system is also found in human cardiomyocytes, which expressed choline acetyltransferase (ChAT) and the vesicular acetylcholine transporter (VAChT). Furthermore, VAChT expression was increased 3‐ and 1.5‐fold at the mRNA and protein level, respectively, in ventricular tissue from patients with heart failure, suggesting increased ACh secretion in disease. We used mice with genetic deletion of cardiomyocyte‐specific VAChT or ChAT and mice overexpressing VAChT to test the functional significance of cholinergic signaling. Mice deficient for VAChT displayed an 8% decrease in fractional shortening and 13% decrease in ejection fraction compared with angiotensin II (Ang II)‐treated control animals, suggesting enhanced ventricular dysfunction and pathologic remodeling in response to Ang II. Similar results were observed in ChAT‐deficient mice. Conversely, no decline in ventricular function was observed in Ang II‐treated VAChT overexpressors. Furthermore, the fibrotic area was significantly greater (P < 0.05) in Ang II‐treated VAChT‐deficient mice (3.61 ± 0.64%) compared with wild‐type animals (2.24 ± 0.11 %). In contrast, VAChT overexpressing mice did not display an increase in collagen deposition. Our results provide new insight into cholinergic regulation of cardiac function, suggesting that a compensatory increase in cardiomyocyte VAChT levels may help offset cardiac remodeling in heart failure.—Roy, A., Dakroub, M., Tezini, G. C. S. V., Liu, Y., Guatimosim, S., Feng, Q., Salgado, H. C., Prado, V. F., Prado, M. A. M., Gros, R. Cardiac acetylcholine inhibits ventricular remodeling and dysfunction under pathologic conditions. FASEB J. 30, 688‐701 (2016). www.fasebj.org

An Analysis of the Myocardial Transcriptome in a Mouse Model of Cardiac Dysfunction with Decreased Cholinergic Neurotransmission

Autonomic dysfunction is observed in many cardiovascular diseases and contributes to cardiac remodeling and heart disease. We previously reported that a decrease in the expression levels of the vesicular acetylcholine transporter (VAChT) in genetically-modified homozygous mice (VAChT KDHOM) leads to decreased cholinergic tone, autonomic imbalance and a phenotype resembling cardiac dysfunction. In order to further understand the molecular changes resulting from chronic long-term decrease in parasympathetic tone, we undertook a transcriptome-based, microarray-driven approach to analyze gene expression changes in ventricular tissue from VAChT KDHOM mice. We demonstrate that a decrease in cholinergic tone is associated with alterations in gene expression in mutant hearts, which might contribute to increased ROS levels observed in these cardiomyocytes. In contrast, in another model of cardiac remodeling and autonomic imbalance, induced through chronic isoproterenol treatment to increase sympathetic drive, these genes did not appear to be altered in a pattern similar to that observed in VAChT KDHOM hearts. These data suggest the importance of maintaining a fine balance between the two branches of the autonomic nervous system and the significance of absolute levels of cholinergic tone in proper cardiac function.

Impact of the epithelial dysplasia grading and Ki67 proliferation index in the adjacent non-malignant mucosa on recurrence and survival in head and neck squamous cell carcinoma.

This study aimed to evaluate the association between several different aspects of disease in head and neck squamous cell carcinoma (HNSCC): morphological grading, Ki67 proliferation index (PI), invasive front, adjacent non-malignant mucosa (ANMM), recurrence and overall survival of the patients. Sixty-four fully reviewed and followed-up patients with primary HNSCC were matched according to recurrence of the lesion and placed in one of two groups of 32 cases. Chi-square and Fishers exact tests were used to analyze the clinicopathological parameters between both groups of patients. Association between Ki67 PI and clinicopathological parameters was also analyzed through chi-square and Fishers exact tests with the binary logistic regression model used as a multivariate analysis. In addition, survival analysis was also performed. Our results showed that high-risk dysplasia in ANMM and high Ki67 PI in ANMM of HNSCC exhibited a higher risk of tumor recurrence. Survival analysis showed that T3/T4 tumor sizes and high Ki67 PI were significantly associated with an increase in the risk of death in multivariate analysis. Our results revealed that high-risk dysplasia and high Ki67 PI of the ANMM are parameters which are indicative of tumor recurrence. Furthermore, T3/T4 tumor sizes and high Ki67 PI in the invasive front appear to be important prognostic tools for HNSCC.

Synthetic triterpenoids inhibit GSK3β activity and localization and affect focal adhesions and cell migration

Synthetic triterpenoids are a class of anti-cancer compounds that target many cellular functions, including apoptosis and cell growth in both cell culture and animal models. We have shown that triterpenoids inhibit cell migration in part by interfering with Arp2/3-dependent branched actin polymerization in lamellipodia (To et al., 2010). Our current studies reveal that Glycogen Synthase Kinase 3 beta (GSK3β), a kinase that regulates many cellular processes, including cell adhesion dynamics, is a triterpenoid-binding protein. Furthermore, triterpenoids were observed to inhibit GSK3β activity and increase cellular focal adhesion size. To further examine whether these effects on focal adhesions in triterpenoid-treated cells were GSK3β-dependent, GSK3β inhibitors (lithium chloride and SB216763) were used to examine cell adhesion and morphology as well as cell migration. Our results showed that GSK3β inhibitors also altered cell adhesion sizes. Moreover, these inhibitors blocked cell migration and displaced proteins at the leading edge of migrating cells, consistent with what was observed in triterpenoid-treated cells. Therefore, the triterpenoids may affect cell migration via a mechanism that targets and alters the activity and localization of GSK3β.