Synthesis of novel 2-pyrazoline analogues with potent anti-inflammatory effect mediated by inhibition of phospholipase A2: Crystallographic,in silico docking and QSAR analysis

Oxidative-stress induces inflammatory diseases. Further, infections caused by drug-resistant microbial strains are on the rise. This necessitates the discovery of novel small-molecules for intervention therapy. A series of 3-(2,3-dichlorophenyl)-1-(aryl)prop-2-en-1-ones are synthesized as intermediates via Claisen-Schmidt reaction approach. Subsequently, these intermediates were transformed into 2-pyrazolines by their reaction with phenylhydrazine hydrochlorides in methanol and few drops of acetic acid under reflux conditions. Synthesized compounds were characterized by spectroscopic, crystallographic and elemental analyses studies and then, were evaluated for their in vitro antimicrobial and anti-inflammatory activities. Amongst the series, 3-(4-chlorophenyl)-5-(2,3-dichlorophenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (5e), 5-(2,3-dichlorophenyl)-3-(4-fluorophenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (5c) and 5-(2,3-dichlorophenyl)-3-(4-methoxyphenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (5h) showed significant inhibition of phospholipase A2 with IC₅₀ values of 10.2, 11.1 and 11.9 µM, respectively. Protein structure modelling and docking studies indicated that the compounds showed binding to a highly conserved calcium-binding pocket on the enzyme. Further, compounds (5e), 1-(3-chlorophenyl)-5-(2,3-dichlorophenyl)-3-phenyl-4,5-dihydro-1H-pyrazole (5b), and 1-(3-chlorophenyl)-3-(4-chlorophenyl)-5-(2,3-dichlorophenyl)-4,5-dihydro-1H-pyrazole (5f) showed excellent antimicrobial activities against various bacterial and fungal strains. In conclusion, this study is a successful attempt at the synthesis and characterization of chalcone derivatives that can target phospholipase A2, an enzyme that is a prominent player in the physiological inflammatory cascade. Thus, these compounds show promise for development as next-generation nonsteroidal anti-inflammatory drugs.     

Neural responses in human superior temporal cortex support coding of voice representations

The ability to recognize abstract features of voice during auditory perception is an intricate feat of human audition. For the listener, this occurs in near-automatic fashion to seamlessly extract complex cues from a highly variable auditory signal. Voice perception depends on specialized regions of auditory cortex, including superior temporal gyrus (STG) and superior temporal sulcus (STS). However, the nature of voice encoding at the cortical level remains poorly understood. We leverage intracerebral recordings across human auditory cortex during presentation of voice and nonvoice acoustic stimuli to examine voice encoding at the cortical level in 8 patient-participants undergoing epilepsy surgery evaluation. We show that voice selectivity increases along the auditory hierarchy from supratemporal plane (STP) to the STG and STS. Results show accurate decoding of vocalizations from human auditory cortical activity even in the complete absence of linguistic content. These findings show an early, less-selective temporal window of neural activity in the STG and STS followed by a sustained, strongly voice-selective window. Encoding models demonstrate divergence in the encoding of acoustic features along the auditory hierarchy, wherein STG/STS responses are best explained by voice category and acoustics, as opposed to acoustic features of voice stimuli alone. This is in contrast to neural activity recorded from STP, in which responses were accounted for by acoustic features. These findings support a model of voice perception that engages categorical encoding mechanisms within STG and STS to facilitate feature extraction.

Voice perception occurs via specialized networks in higher order auditory cortex, but how voice features are encoded remains a central unanswered question. Using human intracerebral recordings of auditory cortex, this study provides evidence for categorical encoding of voice.     

ENaC, renal sodium excretion and extracellular ATP

Sodium balance determines the extracellular fluid volume and sets arterial blood pressure (BP). Chronically raised BP (hypertension) represents a major health risk in Western societies. The relationship between BP and renal sodium excretion (the pressure/natriuresis relationship) represents the key element in defining the BP homeostatic set point. The renin–angiotensin–aldosterone system (RAAS) makes major adjustments to the rates of renal sodium secretion, but this system works slowly over a period of hours to days. More rapid adjustments can be made by the sympathetic nervous system, although the kidney can function well without sympathetic nerves. Attention has now focussed on regulatory mechanisms within the kidney, including extracellular nucleotides and the P2 receptor system. Here, we discuss how extracellular ATP can control renal sodium excretion by altering the activity of epithelial sodium channels (ENaC) present in the apical membrane of principal cells. There remains considerable controversy over the molecular targets for released ATP, although the P2Y₂ receptor has received much attention. We review the available data and reflect on our own findings in which ATP-activated P2Y and P2X receptors make adjustments to ENaC activity and therefore sodium excretion.     

Systematic evaluation of transcellular activities of secretory phospholipases A2. High activity of group V phospholipases A2 to induce eicosanoid biosynthesis in neighboring inflammatory cells

The mechanisms by which secretory phospholipase A2 (PLA2) exerts cellular effects are not fully understood. To elucidate these mechanisms, we systematically and quantitatively assessed the activities of human group IIA, V, and X PLA2s on originating and neighboring cells using orthogonal fluorogenic substrates in various mixed cell systems. When HEK293 cells stably expressing each of these PLA2s were mixed with non-transfected HEK293 cells, group V and X PLA2s showed strong transcellular lipolytic activity, whereas group IIA PLA2 exhibited much lower transcellular activity. The transcellular activity of group V PLA2 was highly dependent on the presence of cell surface heparan sulfate proteoglycans of acceptor cells. Activation of RBL-2H3 and DLD-1 cells that express endogenous group V PLA2 led to the secretion of group V PLA2 and its transcellular action on neighboring human neutrophils and eosinophils, respectively. Similarly, activation of human bronchial epithelial cells, BEAS-2B, caused large increases in arachidonic acid and leukotriene C4 release from neighboring human eosinophils. Collectively, these studies show that group V and X PLA2s can act transcellularly on mammalian cells and suggest that group V PLA2 released from neighboring cells may function in triggering the activation of inflammatory cells under physiological conditions.     

Changes to respiratory mechanisms during speech as a result of different cues to increase loudness.

The purpose of the present study was to determine whether different cues to increase loudness in speech result in different internal targets (or goals) for respiratory movement and whether the neural control of the respiratory system is sensitive to changes in the speaker's internal loudness target. This study examined respiratory mechanisms during speech in 30 young adults at comfortable level and increased loudness levels. Increased loudness was elicited using three methods: asking subjects to target a specific sound pressure level, asking subjects to speak twice as loud as comfortable, and asking subjects to speak in noise. All three loud conditions resulted in similar increases in sound pressure level . However, the respiratory mechanisms used to support the increase in loudness differed significantly depending on how the louder speech was elicited. When asked to target at a particular sound pressure level, subjects used a mechanism of increasing the lung volume at which speech was initiated to take advantage of higher recoil pressures. When asked to speak twice as loud as comfortable, subjects increased expiratory muscle tension, for the most part, to increase the pressure for speech. However, in the most natural of the elicitation methods, speaking in noise, the subjects used a combined respiratory approach, using both increased recoil pressures and increased expiratory muscle tension. In noise, an additional target, possibly improving intelligibility of speech, was reflected in the slowing of speech rate and in larger volume excursions even though the speakers were producing the same number of syllables.     

Effects of light dynamics on coral spawning synchrony

Synchrony of spawning in many hermatypic corals, typically a few nights after the full moon, is putatively dependent on solar and lunar light cycles in conjunction with other possible cues such as tides and temperature. We analyze here the contributions of separate components of light dynamics, because the effects of twilight and lunar skylight on coral spawning synchrony have previously been conflated and the alternative hypothesis that these components have differential contributions as proximate cues has not been tested. Moonlight-dependent changes in spectra during twilight, rates of decreasing twilight intensities, and changes in lunar photoperiod were experimentally decoupled using programmed light-emitting diodes and compared for their separate effects on spawning synchrony in Acropora humilis. Effects on synchrony under the control of synthetic lunar cues were greatest in response to changes in lunar photoperiod; changes in light intensities and spectra had lesser influence. No significant differences among treatment responses were found at the circa-diel time scale. We conclude that spawning synchrony on a particular lunar night and specific time of night is a threshold response to differential periods of darkness after twilight that is primarily influenced by lunar photoperiod and secondarily by discrete optical components of early nocturnal illumination.     

Crystal structures of open and closed forms of d-serine deaminase from Salmonella typhimurium - implications on substrate specificity and catalysis

Metabolism of D-amino acids is of considerable interest due to their key importance in cell structure and function. Salmonella typhimuriumd-serine deaminase (StDSD) is a pyridoxal 5' phosphate (PLP) dependent enzyme that catalyses degradation of D-Ser to pyruvate and ammonia. The first crystal structure of d-serine deaminase described here reveals a typical Foldtype II or tryptophan synthase β subunit fold of PLP-dependent enzymes. Although holoenzyme was used for crystallization of both wild-type StDSD (WtDSD) and selenomethionine labelled StDSD (SeMetDSD), significant electron density was not observed for the cofactor, indicating that the enzyme has a low affinity for the cofactor under crystallization conditions. Interestingly, unexpected conformational differences were observed between the two structures. The WtDSD was in an open conformation while SeMetDSD, crystallized in the presence of isoserine, was in a closed conformation suggesting that the enzyme is likely to undergo conformational changes upon binding of substrate as observed in other Foldtype II PLP-dependent enzymes. Electron density corresponding to a plausible sodium ion was found near the active site of the closed but not in the open state of the enzyme. Examination of the active site and substrate modelling suggests that Thr166 may be involved in abstraction of proton from the Cα atom of the substrate. Apart from the physiological reaction, StDSD catalyses α, β elimination of D-Thr, D-Allothr and L-Ser to the corresponding α-keto acids and ammonia. The structure of StDSD provides a molecular framework necessary for understanding differences in the rate of reaction with these substrates.     

3-D warped discrete cosine transform for MRI image compression

Image compression is an application of data compression on digital images. Several lossy/lossless transform coding techniques are used for image compression. Discrete cosine transform (DCT) is one such widely used technique. A variation of DCT, known as warped discrete cosine transform (WDCT), is used for 2-D image compression and it is shown to perform better than the DCT at high bit-rates. We extend this concept and develop the 3-D WDCT, a transform that has not been previously investigated. We outline some of its important properties, which make it especially suitable for image compression. We then propose a complete image coding scheme for volumetric data sets based on the 3-D WDCT scheme. It is shown that the 3-D WDCT-based compression scheme performs better than a similar 3-D DCT scheme for volumetric data sets at high bit-rates.