Dillip K. Mohanty

Vibrational characterization of azobenzenes, azoxybenzenes and azoaromatic and azoxyaromatic polyethers

Raman and infrared spectra of a bisphenol-A-containing azoaromatic polyether, a bisphenol-A-containing azoxyaromatic polyether and a bisphenol-A-containing 2-hydroxyazoaromatic polyether were analyzed. Vibrational spectra were also collected for the corresponding model compounds 4,4′-(4-tert-butylphenoxy)azobenzene, 4,4′-(4-tert-butylphenoxy)azoxybenzene and 4,4′-(4-tert-butylphenoxy)-2-hydroxyazobenzene. Comparisons with substituted azobenzenes and azoxybenzenes were used in assigning the spectra in the 1650–900 cm-1 region. Assignments of the N=N stretch (1410–1390 cm-1) demonstrate that all of the compounds are in the trans configuration. The azo bridge vibrations of the azoaromatic ethers are very similar to those of azobenzene. Different types of hydrogen bonding are seen in the 2-hydroxyazoaromatic compounds. The polyether has an OH stretch at 3355 cm-1 which indicates a network of intermolecular hydrogen bonds among the polymers. The 2-hydroxyazoaromatic model compound has no IR peak above 3100 cm-1 and N=N, CO and CN stretches which are shifted due to an intramolecular hydrogen bond with the azo nitrogen. The N=N stretch of the azoxyaromatic ethers is at the same wavenumber as in the azo compounds. Assignment of the N→O stretch vibration is difficult because of mixing with other modes of the azoxy bridge.

Sustained nitric oxide (NO)-releasing compound reverses dysregulated NO signal transduction in priapism

We evaluated the therapeutic potential of a sustained nitric oxide (NO)‐releasing compound to correct the molecular hallmarks and pathophysiology of priapism, an important but poorly characterized erectile disorder. 1,5‐Bis‐(dihexyl‐N‐nitrosoamino)‐2,4‐dinitrobenzene (C6′) and an inactive form of the compound [1,5‐bis‐(dihexylamino)‐2,4‐dinitrobenzene (C6)] were tested in neuronal cell cultures and penile lysates for NO release (Griess assay) and biological activity (cGMP production). The effect of local depot C6′ or C6 was evaluated in mice with a priapic phenotype due to double neuronal and endothelial NO synthase deletion (dNOS‐/‐) or human sickle hemoglobin transgenic expression (Sickle). Changes in NO signaling molecules and reactive oxygen species (ROS) surrogates were assessed by Western blot. The physiological response after C6′ treatment was assessed using an established model of electrically stimulated penile erection. C6′ generated NO, increased cGMP, and dose dependently increased NO metabolites. C6′ treatment reversed abnormalities in key penile erection signaling molecules, including phosphodiesterase type 5, phosphorylated endothelial nitric oxide synthase, and phosphorylated vasodilator‐stimulated phosphoprotein. In Sickle mice, C6′ also attenuated the increased ROS markers gp91phox, 4‐hydroxynonenal, and 3‐nitrotyrosine. Finally, C6′ corrected the excessive priapic erection response of dNOS‐/‐ mice. Exogenous sustained NO release from C6′ corrects pathological erectile signaling in mouse models of priapism and suggests novel approaches to human therapy.—Lagoda, G., Sezen, S. F., Hurt, K. J., Cabrini, M. R., Mohanty, D. K., Burnett, A. L. Sustained nitric oxide (NO)‐releasing compound reverses dysregulated NO signal transduction in priapism. FASEB J. 28, 76–84 (2014). www.fasebj.org

Nicotine exposure induces bronchial epithelial cell apoptosis and senescence via ROS mediated autophagy-impairment

Waterpipe smoking and e-cigarette vaping, the non-combustible sources of inhaled nicotine exposure are increasingly becoming popular and marketed as safer alternative to cigarette smoking. Hence, this study was designed to investigate the impact of inhaled nicotine exposure on disease causing COPD-emphysema mechanisms. For in vitro studies, human bronchial epithelial cells (Beas2b) were treated with waterpipe smoke extract (WPSE, 5%), nicotine (5mM), and/or cysteamine (250μM, an autophagy inducer and anti-oxidant drug), for 6hrs. We observed significantly (p<0.05) increased ubiquitinated protein-accumulation in the insoluble protein fractions of Beas2b cells treated with WPSE or nicotine that could be rescued by cysteamine treatment, suggesting aggresome-formation and autophagy-impairment. Moreover, our data also demonstrate that both WPSE and nicotine exposure significantly (p<0.05) elevates Ub-LC3β co-localization to aggresome-bodies while inducing Ub-p62 co-expression/accumulation, verifying autophagy-impairment. We also found that WPSE and nicotine exposure impacts Beas2b cell viability by significantly (p<0.05) inducing cellular apoptosis/senescence via ROS-activation, as it could be controlled by cysteamine, which is known to have an anti-oxidant property. For murine studies, C57BL/6 mice were administered with inhaled nicotine (intranasal, 500μg/mouse/day for 5 days), as an experimental model of non-combustible nicotine exposure. The inhaled nicotine exposure mediated oxidative-stress induces autophagy-impairment in the murine lungs as seen by significant (p<0.05, n=4) increase in the expression levels of nitrotyrosine protein-adduct (oxidative-stress marker, soluble-fraction) and Ub/p62/VCP (impaired-autophagy marker, insoluble-fraction). Overall, our data shows that nicotine, a common component of WPS, e-cigarette vapor and cigarette smoke, induces bronchial epithelial cell apoptosis and senescence via ROS mediated autophagy-impairment as a potential mechanism for COPD-emphysema pathogenesis.

Poly(aryl ether ketone) synthesis via competing SNAR and SRN1 reactions: 1. Polymers derived from 1,3-bis(p-chlorobenzoyl)benzene and 1,3-bis(p-fluorobenzoyl)benzene with hydroquinone and 4,4′-isopropylidenediphenol

Abstract Poly(aryl ether ketone)s were synthesized by the reaction of 1,3-(bischlorobenzoyl)benzene or the corresponding fluoro analogue with bisphenoxides derived from either hydroquinone or 4,4′-isopropylidenebiphenol (bisphenol-A). With the stronger nucleophile, obtained from bisphenol-A, and either of the dihalides, high molecular weight polymers are formed exclusively via a nucleophilic aromatic substitution (SNAR) reaction. A similar reaction leads to the formation of a high molecular weight polymer when the weaker nucleophile, derived from hydroquinone, is allowed to react with the bisfluoride. On the other hand, oligomeric products are obtained when the bischloride is treated with this weaker nucleophile. In this case, both SNAR and SRN1 (substitution, radical-nucleophilic, unimolecular) mechanisms are operative for the replacement of the chlorine atoms. The SRN1 pathway, which is responsible for the formation of oligomeric products, can be eliminated by the addition of a suitable radical scavenger. High molecular weight poly(aryl ether ketone) is then formed via the SNAR mechanism.

Effects of slow, sustained, and rate-tunable nitric oxide donors on human aortic smooth muscle cells proliferation.

Smooth muscle cell (SMC) proliferation has been accepted as a common event in the pathophysiology of vascular diseases, including atherogenesis and intimal hyperplasia. Delivery of the nitric oxide synthase (NOS) substrate l‐arginine, pharmacological nitric oxide (NO) donors, NO gas or overexpression of NOS proteins can inhibit SMC proliferation and reduce the injury responses within the blood vessel wall. Although commercial development of NO donors that attempt to provide exogenous delivery of NO has accelerated over the last few years, none of the currently available products can provide controlled, sustained, time‐tunable release of NO. Nitrosamine‐based NO donors, prepared in our laboratory, present a unique and innovative alternative for possible treatments for long‐term NO deficiency‐related diseases, including atherosclerosis, asthma, erectile dysfunction, cancer, and neurodegenerative diseases. A family of secondary amines prepared via nucleophilic aromatic displacement reactions could be readily N‐nitrosated to produce NO donors. NO release takes place in three distinct phases. During the initial phase, the release rate is extremely fast. In the second phase, the release is slower and the rate remains essentially the same during the final stage. These compounds inhibited up to 35% human aortic smooth muscle cell proliferation in a concentration‐dependent manner.

Preparation and properties of novel aromatic poly(thioethers) derived from 4,4′‐thiobisbenzenethiol

A series of amorphous and semicrystalline aromatic poly(thioethers) have been prepared by the reactions of 4,4′-thiobisbenzenethiol and activated dihalides. Azo group activated dihalide monomer was prepared by the reactions of 4-fluoronitrosobenzene with a suitable diamine. The keto and phosphine sulfide containing monomers were synthesized by Friedel-Crafts acylation reactions of suitable halobenzenes with appropriate acid chlorides. Potassium carbonate mediated reactions in dimethylacetamide afforded moderate to high molecular weight polymers. Polymers with high melting points were prepared by using diphenyl sulfone as a co-solvent. The poly(thioethers) exhibit high glass transition temperatures and/or high melting points. In addition, the polymers exhibit excellent thermal stability.

Slow and sustained nitric oxide releasing compounds inhibit multipotent vascular stem cell proliferation and differentiation without causing cell death

Atherosclerosis is the leading cause of cerebral and myocardial infarction. It is believed that neointimal growth common in the later stages of atherosclerosis is a result of vascular smooth muscle cell (SMC) de-differentiation in response to endothelial injury. However, the claims of the SMC de-differentiation theory have not been substantiated by monitoring the fate of mature SMCs in response to such injuries. A recent study suggests that atherosclerosis is a consequence of multipotent vascular stem cell (MVSC) differentiation. Nitric oxide (NO) is a well-known mediator against atherosclerosis, in part because of its inhibitory effect on SMC proliferation. Using three different NO-donors, we have investigated the effects of NO on MVSC proliferation. Results indicate that NO inhibits MVSC proliferation in a concentration dependent manner. A slow and sustained delivery of NO proved to inhibit proliferation without causing cell death. On the other hand, larger, single-burst NO concentrations, inhibits proliferation, with concurrent significant cell death. Furthermore, our results indicate that endogenously produced NO inhibits MVSC differentiation to mesenchymal-like stem cells (MSCs) and subsequently to SMC as well.

Secondary amines containing one aromatic nitro group: preparation, nitrosation, sustained nitric oxide release, and the synergistic effects of released nitric oxide and an arginase inhibitor on vascular smooth muscle cell proliferation.

Atherosclerosis, a leading cause of death worldwide, is associated with the excessive proliferation of vascular smooth muscle cells. Nitrogen monoxide, more commonly known as nitric oxide, inhibits this uncontrolled proliferation. Herein we report the preparation of two families of nitric oxide donors; beginning with the syntheses of secondary amine precursors, obtained through the reaction between 2 equiv of various monoamines with 2,4 or 2,6-difluoronitrobenzene. The purified secondary amines were nitrosated then subjected to a Griess reagent test to examine the slow and sustained nitric oxide release rate for each compound in both the absence and presence of reduced glutathione. The release rate profiles of these two isomeric families of NO-donors were strongly dependent on the number of side chain methylene units and the relative orientations of the nitro groups with respect to the N-nitroso moieties. The nitrosated compounds were then added to human aortic smooth muscle cell cultures, individually and in tandem with S-2-amino-6-boronic acid (ABH), a potent arginase inhibitor. Cell viability studies indicated a lack of toxicity of the amine precursors, in addition to anti-proliferative effects exhibited by the nitrosated compounds, which were enhanced in the presence of ABH.

Competing reactions for poly(aryl ether ketone) synthesis: 2. Preparationof high molecular weight polymer from hydroquinoneand 1,3-bis(4-chlorobenzoyl)benzene

Abstract High molecular weight semicrystalline poly(aryl ether ketone)s have been prepared from hydroquinone and 1,3-bis(4-chlorobenzoyl)benzene in diphenylsulfone and anhydrous potassium carbonate with or without toluene. The use of this solvent system, instead of a combination of dimethylacetamide, diphenylsulfone and toluene, results in the elimination of SR,,I (radical nucleophilic, unimolecular substitution) processes and the formation of high molecular weight polymer takes place entirely via SNAR (nucleophilic aromatic substitution) reactions.

1,3‐Bis(ethylamino)‐2‐nitrobenzene, 1,3‐bis(n‐octylamino)‐2‐nitrobenzene and 4‐ethylamino‐2‐methyl‐1H‐benzimidazole

1,3-Bis(ethylamino)-2-nitrobenzene, C(10)H(15)N(3)O(2), (I), and 1,3-bis(n-octylamino)-2-nitrobenzene, C(22)H(39)N(3)O(2), (II), are the first structurally characterized 1,3-bis(n-alkylamino)-2-nitrobenzenes. Both molecules are bisected though the nitro N atom and the 2-C and 5-C atoms of the ring by twofold rotation axes. Both display intramolecular N-H...O hydrogen bonds between the amine and nitro groups, but no intermolecular hydrogen bonding. The nearly planar molecules pack into flat layers ca 3.4 A apart that interact by hydrophobic interactions involving the n-alkyl groups rather than by pi-pi interactions between the rings. The intra- and intermolecular interactions in these molecules are of interest in understanding the physical properties of polymers made from them. Upon heating in the presence of anhydrous potassium carbonate in dimethylacetamide, (I) and (II) cyclize with formal loss of hydrogen peroxide to form substituted benzimidazoles. Thus, 4-ethylamino-2-methyl-1H-benzimidazole, C(10)H(13)N(3), (III), was obtained from (I) under these reaction conditions. Compound (III) contains two independent molecules with no imposed internal symmetry. The molecules are linked into chains via N-H...N hydrogen bonds involving the imidazole rings, while the ethylamino groups do not participate in any hydrogen bonding. This is the first reported structure of a benzimidazole derivative with 4-amino and 2-alkyl substituents.