Babul Kumar Bezbaruah

Targeting poly(ADP-ribose)polymerase1 in neurological diseases: A promising trove for new pharmacological interventions to enter clinical translation

The highly conserved abundant nuclear protein poly(ADP-ribose)polymerase1 (PARP1) functions at the center of cellular stress response and is mainly implied in DNA damage repair mechanism. Apart from its involvement in DNA damage repair, it does sway multiple vital cellular processes such as cell death pathways, cell aging, insulator function, chromatin modification, transcription and mitotic apparatus function. Since brain is the principal organ vulnerable to oxidative stress and inflammatory responses, upon stress encounters robust DNA damage can occur and intense PARP1 activation may result that will lead to various CNS diseases. In the context of soaring interest towards PARP1 as a therapeutic target for newer pharmacological interventions, here in the present review, we are attempting to give a silhouette of the role of PARP1 in the neurological diseases and the potential of its inhibitors to enter clinical translation, along with its structural and functional aspects.

Poly (ADP-ribose) polymerase-1 inhibitor, 3-aminobenzamide pretreatment ameliorates lipopolysaccharide-induced neurobehavioral and neurochemical anomalies in mice.

Poly (ADP-ribose) polymerase-1 (PARP-1) functions at the center of cellular stress and sways the immune system at several key points, thus modulates inflammatory diseases. The antiinflammatory properties of PARP-1 inhibitors have been demonstrated ameliorating effect in various neuroinflammatory disorders. It has been reported that there is a close relationship between the inflammatory processes and major depressive disorder. In the present study, we have elucidated the role of oxidative-nitrosative stress-PARP-1 pathway in lipopolysaccharide (LPS)-induced neurobehavioral and neurochemical alterations in mice. 3-Aminobenzamide (10 and 30mg/kg) and imipramine (10 and 30mg/kg) were administered once daily for 14days. Mice were challenged with LPS (1mg/kg, i.p.) 30min after drug administration on the 14th day. The mRNA expression level of PARP-1 (12h after LPS injection) in the hippocampus was measured through quantitative real-time PCR. All the behavioral and biochemical parameters were assessed at 24h after LPS injection. The expression level of PARP-1mRNA was found significantly up-regulated in the hippocampus at 12h after LPS administration. Results showed that the LPS-challenged mice exhibited an increase in immobility time seen in forced swimming test and tail suspension test. LPS increased the levels of proinflammatory cytokines and oxido-nitrosative stress parameters in the hippocampus. However, pretreatment with 3-aminobenzamide (30mg/kg) significantly reversed the LPS-induced alterations in behavioral parameters, proinflammatory cytokines, oxidative-nitrosative stress and PARP-1 mRNA levels. Imipramine failed to prevent the up-regulation of PARP-1 induced by LPS administration. Our results emphasized that oxidative-nitrosative stress-PARP-1 cascade can play a key role in LPS-induced neurobehavioral and neurochemical anomalies.

Vancomycin-resistant enterococci: Troublemaker of the 21st century.

The emergence of multidrug-resistant and vancomycin-resistant enterococci during the last decade has made it difficult to treat nosocomial infections. Although various enterococcal species have been identified, only two (Enterococcus faecalis and Enterococcus faecium) are responsible for the majority of human infections. Vancomycin is an important therapeutic alternative against multidrug-resistant enterococci but is associated with a poor prognosis. Resistance to vancomycin dramatically reduces the therapeutic options for enterococcal infections. The bacterium develops resistance by modifying the C-terminal d-alanine of peptidoglycan to d-lactate, creating a d-Ala-d-Lac sequence that effectively reduces the affinity of vancomycin for the peptidoglycan by 1000-fold. Moreover, the resistance genes can be transferred from enterococci to Staphylococcus aureus, thereby posing a threat to patient safety and also a challenge for treating physicians. Judicious use of vancomycin and broad-spectrum antibiotics must be implemented, but strict infection control measures must also be followed to prevent nosocomial transmission of these organisms. Furthermore, improvements in clinical practice, rotation of antibiotics, herbal drugs, nanoantibiotics and the development of newer antibiotics based on a pharmacogenomic approach may prove helpful to overcome dreadful vancomycin-resistant enterococcal infections.

Disparity in actions of rosiglitazone against cisplatin-induced nephrotoxicity in female Sprague-Dawley rats

Cisplatin is one of the most common chemotherapeutic drugs used against various solid, tumours. Despite of its therapeutic benefits, its use in clinical practice is often limited because of dose, related toxicity. The nephrotoxic potential of cisplatin has been ascribed to its accumulation in the, renal tubular cells generating reactive oxygen species (ROS), activation of Bax, increased secretion of, TNFα and activation of certain inflammatory mediators like cytokines. The present investigation was, undertaken with an objective to study the effect of rosiglitazone against cisplatin induced, nephrotoxicity. Pretreatment of rosiglitazone prevents cisplatin induced nephrotoxicity which was, clearly evident from the renal biochemical parameters like reduced BUN, creatinine and TNFα levels, and increased albumin levels, which was also supported by histopathological studies of the kidneys. In contrast, posttreatment of rosiglitazone was not able to protect the renal damage in cisplatin induced, renal toxicity. These results showed the variation of pre & posttreatment effects of rosiglitazone, against the cisplatin induced nephrotoxicity.

Epigenetic Modifications, Alcoholic Brain and Potential Drug Targets

Acute and chronic alcohol exposure evidently influences epigenetic changes, both transiently and permanently, and these changes in turn influence a variety of cells and organ systems throughout the body. Many of the alcohol-induced epigenetic modifications can contribute to cellular adaptations that ultimately lead to behavioral tolerance and alcohol dependence. The persistence of behavioral changes demonstrates that long-lasting changes in gene expression, within particular regions of the brain, may contribute importantly to the addiction phenotype. The research activities over the past years have demonstrated a crucial role of epigenetic mechanisms in causing long lasting and transient changes in the expression of several genes in diverse tissues, including brain. This has stimulated recent research work that is aimed at characterizing the influence of epigenetic regulatory events in mediating the long lasting and transient effects of alcohol abuse on the brain in humans and animal models of alcohol addiction. In this study, we update our current understanding of the impact of alcohol exposure on epigenetic mechanisms in the brain and refurbish the knowledge of epigenetics in the direction of new drugs development.

Multiple facets of poly（ADP-ribose） polymerase- 1 in neurological diseases

The highly conserved abundant nuclear protein poly (ADP-ribose) polymerase-1 (PARP-1) is activated by DNA damage. PARP-1 activation is associated in DNA repair, cell death and inflammation. Since oxidative stress induced robust DNA damage and wide spread inflammatory responses are common pathologies of various CNS diseases, the attention towards PARP-1 as a therapeutic target has been amplifying. This review highlights the multiple roles of PARP-1 in neurological diseases and potential of PARP-1 inhibitors to enter clinical translation. Activity of PARP-1 in physiology and patho-physiology: PARP-1 is an abundant nuclear enzyme consisting of three domains: N-terminal DNA binding domain containing two zinc fingers, auto-modification domain and catalytical domain. PARP-1 functions as a sensor of DNA damage and to bind to DNA breaks/nicks through Zn finger domains. Upon activation PARP-1 synthesizes poly ADP-ribose polymers by catalyzing nicotinamide adenine dinucleo tide (NAD+) into nicotinamide and ADP-ribose, which are then used as substrates to form linear or branched polymers (poly(ADP-riboses); PARs). These polymers of ADP-ribose units then covalently attached to Glu, Lys or Asp residues of acceptor proteins (heteromodification) or onto PARP1 itself (automodification). The high negative charge of PAR dramatically affects the function of target proteins, leading to electrostatic repulsion among histone proteins and DNA, a process implicated in chromatin remodeling, DNA repair and transcriptional regulation. However, the covalent modification of proteins by the transfer of ADP-ribose residues is only momentary due to the rapid action of a group of enzymes including, poly(ADP-ribose) glycohydrolase (PARG), ADP-ribosyl hydrolase3 (ARH3), nucleoside diphosphate linked to another moiety X (NUDIX) and macrodomain containing proteins (MDCPs) which catalyze the hydrolysis of these polymers into free ADP-ribose (ADPR) units (Sriram et al., 2014). Besides to the inception DNA repair mechanism, PARP-1 activity is found to be vital for epigenetic regulation of mitochondrial DNA repair and transcription as well (Lapucci et al., 2011). Furthermore, the activity of PARP-1 is also essential for a vital epigenetic mechanism, DNA methylation (Lodhi et al., 2014). PARP-1 acts at the center of cellular stress. Oxidative stress causes DNA damage and consequently activates PARP-1 to repair the damaged DNA (Krietsch et al., 2012). PARP-1 has been implicated in neuronal pathology, as the brain is highly susceptible to oxidative stress. The degree of the PARylation in response to DNA damage largely depends on the nature and amount of DNA breaks produced. For low levels of DNA damage, PARP1 activity favors repair and survival by interacting with DNA repair enzyme cascade, such as such as XRCC1 and DNA-dependent protein. Moderate DNA damage leads to apoptotic cell death, during which PARP1 will be cleaved into two fragments by caspases. Cleavage of PARP1 is assumed to foil the activation of PARP1 by DNA damage and thereby it prevents cells from pathological consequences such as necrosis of cells. For extensive DNA injury as observed during ischemia/reperfusion and inflammatory conditions, the massive production of PAR ultimately causes cell-death via at least two distinct mechanisms: energy-failure induced necrosis or apoptosis-inducing factor (AIF) dependent apoptosis (Sriram et al., 2014). In the cells with extensive DNA damage or damage that is not repaired, PARP1 remains activated, leading to continued NAD+ depletion and further ATP consumption in order to resynthe-size NAD+ (Berger et al., 1983). Continued NAD+ depletion has also been shown to induce a rapid mitochondrial dysfunction, which was followed by a collapse in mitochondrial potential, and the release of AIF and cytochrome c (Alano et al., 2010). The released AIF thus mediates the caspase-independent cell death termed parthanatos. In contrast to its name, AIF is now further acknowledged as a necrotic rather than an apoptotic mediator, providing further support for the necrotic role of PARylation. Thus it is can be inferred that inhibition of elevated PARylation could be beneficial (Figure 1) (Sriram et al., 2014). Figure 1 Diagram representing the activity of ADP-ribosylation and consequences. Impact of PARP-1 in neurological diseases: As aforesaid, PARP-1 has been implicated in neuronal pathology, as the brain is highly susceptible to oxidative stress. We can go for the inhibition of PARylation for minimizing or nullifying the harmful effects of elevated oxidative-nitrosative stress. PARP-1 is the main enzyme responsible for PARylation, so inhibiting this enzyme could be useful in this regard. In the laboratory there are different types of models (in vitro and in vivo) for studying the possible protective role of PARP-1 inhibition. In the in vivo models PARP-1 inhibition can be achieved in two ways either by using knockout animal models or by using chemical inhibition, while in vitro models equip the cell lines which are devoid of PARP-1 gene. As inferred theoretically, even the results from many studies (in vitro and in vivo) have revealed the promising neuro-protective role of PARP-1 inhibition (Sriram et al., 2014). There are many neurological indications, in which PARP-1 has been studied extensively such as stroke, traumatic brain injury, neurodegenerative diseases (Parkinsons disease, Alzheimers disease and amyotrophic lateral sclerosis) and neuro-inflmmatory diseases such as multiple sclerosis. Almost all the studies revealed a unique conclusion, that is targeting PARP-1 in neurological is a promising approach for minimizing the harmful effects of oxidative-nitrosative stress (Jangra et al., 2013; Martire et al., 2013; Rulten et al., 2014; Sriram et al., 2014). Among the neurological diseases stroke is extensively studied indication for the impact of PARP-1. The results from many studies have proved the protective impact of PARP-1 inhibition in stroke. A recent break through study by Matsuura and group has further enriched the concept of protective role PARP-1 inhibition in stroke. They have reported the outstanding findings from their study of PARP-1 inhibitor, MP-124 in cynomolgus and rhesus monkeys. Even the results from that particular study are in compliant with recommendations laid by Stroke Therapy Academic Industry Roundtable (STAIR). The magnitude of the therapeutic effect, as well as the therapeutic window of intervention is important while dealing with cerebral stroke and ischemia. The therapeutic window of PARP-1 inhibitor is making them an attractive class of drugs for these indications, as a very few number of drugs show such a good therapeutic window. However, presently a phase-1 clinical study of PARP1 inhibitor, JPI-289 is underway for stroke (Matsuura et al., 2011; Moroni et al., 2012; Sriram et al., 2014). In addition, several PARP-1 inhibitors are in different clinical phases of development as a single and combined therapy for the cancer indications ranging from solid tumors to breast cancers (Sriram et al., 2014). To be honest the exploration of impact PARP1 in the other central nervous system diseases is a bit late as compared to stroke. It is still better in the case of traumatic brain injury as compared to neurodegenerative diseases (Alzheimers and Parkinsons) and neuroinflammatory diseases such as multiple sclerosis. Apart from stroke, the results from several studies of PARP-1 in different neurological models are also providing potential evidence of the approach (Sriram et al., 2014; Stoica et al., 2014) Conclusion and future perspectives: Extreme severity and restricted clinical options are making neurological indications more difficult to handle. However, the treatment with PARP-1 inhibitors showing promising results for neurological indications in multiple preclinical studies. Now PARP-1 could be reliable target for newer drug developments in the field of neurological diseases. In spite of this much propitious situation, PARP-1 inhibition therapy has its own set of limitations. The primary function of PARP1 is in DNA-damage repair, widespread PARP-1 inhibition may leave cells with larger number of DNA anomalies which may amplify the risk of genomic instability. Surviving neurons with DNA damage might be dysfunctional and thus later on undergo apoptosis. Additionally, the prolonged PARP-1 inhibition might have negative effects beyond the genetic stability. In addition, at present the available drugs are not exceptionally specific for PARP-1. To combat these issues some more studies are still required to corroborate the safety of the therapeutic approach.

Cognitive deficits induced by combined exposure of stress and alcohol mediated through oxidative stress-PARP pathway in the hippocampus

Several studies reported that stress can enhance the consumption of alcohol in humans and animals. However, the combinatorial effect of stress and alcohol on cognitive function and neurochemical alterations is quite understudied. In the present study, we have elucidated the involvement of oxidative stress-PARP cascade in alcohol and restraint stress (RS)-exposed animals using a PARP inhibitor, 1,5-isoquinolinediol (3mg/kg for 14days). Male Swiss albino mice were given alcohol (ALC) or RS (2h per day) or both in ALC+RS group for 28days. Behavioral analysis revealed cognitive dysfunction in ALC+RS group. Furthermore, oxidative stress and raised level of pro-inflammatory cytokines were found in the hippocampus region of ALC+RS group. Semi-quantitative reverse transcriptase PCR showed overactivation of PARP-1 gene in ALC+RS group. 1,5-isoquinolinediol treatment significantly prevented cognitive deficits and aforementioned neurochemical alterations. Overall, our findings showed that ALC+RS exerted deleterious effects on the hippocampus which involves oxidative stress-PARP overactivation cascade.

Prescribing pattern of analgesics in orthopedic in-patient department at tertiary care hospital in Guwahati, Assam, Northeast India

Objectives: The aim of this study is to evaluate the prescribing pattern of analgesics and analyze the rational use of analgesic in orthopedic in-patient department of tertiary care teaching hospital, Guwahati, Assam. Subjects and Methods: An observational and cross-sectional study was carried out for 1 month from April to May 2014. Collected data included age, sex, diagnosis and line of management during the study. The generic name and the average cost of treatment per patient were evaluated using Indian Drug Review, 2014. The prescribed drugs were assessed with respective National Model List of Essential Medicines (NLEM), 2011 and the rationality of prescriptions was determined using the World Health Organization indicators of drug utilization. The patients’ details were recorded in a predeigned data collection form and results were analyzed by descriptive statistics. Results: Out of 200 patients, 123 were male and 77 were female. The average number of analgesic per prescription was 1.46. In this study, 55.5% of patients had received single analgesic. Diclofenac was the most commonly prescribed analgesic (43.49%). During hospitalization, majority of the patients have received parenteral preparation. Gastroprotective agents and antimicrobials were frequently prescribed along with analgesics. Out of 292 analgesics prescribed, 183 (62.67%) were from the NLEM, India. Furthermore, 176 (57.19%) analgesics were prescribed by generic name. The average cost of treatment per patient was 2151.72 INR. Utilization of analgesic in terms of defined daily dose/100 bed-days was 104.01. Conclusion: The percentages of analgesics prescribing from NLEM and the use of analgesic by generic name were found satisfactory. Regular educational interventions to improve prescribing practices among physicians at different levels may further promote rational prescribing.