Targeting phosphodiesterase 4 as a potential therapy for Parkinson's disease: a review.

Phosphodiesterases (PDEs) have become a promising therapeutic target for various disorders. PDEs are a vast and diversified family of enzymes that degrade cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which have several biochemical and physiological functions. Phosphodiesterase 4 (PDE4) is the most abundant PDE in the central nervous system (CNS) and is extensively expressed in the mammalian brain, where it catalyzes the hydrolysis of intracellular cAMP. An alteration in the balance of PDE4 and cAMP results in the dysregulation of different biological mechanisms involved in neurodegenerative diseases. By inhibiting PDE4 with drugs, the levels of cAMP inside the cells could be stabilized, which may improve the symptoms of mental and neurological disorders such as memory loss, depression, and Parkinson's disease (PD). Though numerous studies have shown that phosphodiesterase 4 inhibitors (PDE4Is) are beneficial in PD, there are presently no approved PDE4I drugs for PD. This review presents an overview of PDE4Is and their effects on PD, their possible underlying mechanism in the restoration/protection of dopaminergic cell death, which holds promise for developing PDE4Is as a treatment strategy for PD. Methods on how these drugs could be effectively delivered to develop as a promising treatment for PD have been suggested.

Neuroprotective potential of traditionally used medicinal plants of Manipur against rotenone-induced neurotoxicity in SH-SY5Y neuroblastoma cells.

ETHNOPHARMACOLOGICAL RELEVANCE: Alternanthera sessilis (L.) R. Br. ex DC., Eryngium foetidum L., and Stephania japonica (Thunb.) Miers plants are traditionally used to treat various central nervous system disorders like paralysis, epilepsy, seizure, convulsion, chronic pain, headache, sleep disturbances, sprain, and mental disorders. However, their possible neuroprotective effects have not been evaluated experimentally so far. AIM OF THE STUDY: The study aims to examine the neuroprotective potential of the three plants against cytotoxicity induced by rotenone in SH-SY5Y neuroblastoma cells and assess its plausible mechanisms of neuroprotection. MATERIALS AND METHODS: The antioxidant properties of the plant extracts were determined chemically by DPPH and ABTS assay methods. The cytotoxicity of rotenone and the cytoprotective activities of the extracts were evaluated using MTT assays. Microtubule-associated protein 2 (MAP2) expression studies in cells were performed to assess neuronal survival after rotenone and extract treatments. Mitochondrial membrane potential and intracellular levels of reactive oxygen species were evaluated using Rhodamine 123 and DCF-DA dye, respectively. Catalase, glutathione peroxidase, and superoxide dismutase activities were also measured. Apoptotic nuclei were examined using DAPI staining. Liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (LC-QTOF-MS) analysis of the plant extracts was also performed. RESULTS: The methanol extracts of A. sessilis, S. japonica, and E. foetidum showed excellent free radical scavenging activities. MAP2 expression studies show that A. sessilis and S. japonica have higher neuroprotective effects against rotenone-induced neurotoxicity in SH-SY5Y cells than E. foetidum. Pre-treating cells with the plant extracts reverses the rotenone-induced increase in intracellular ROS. The plant extracts could also restore the reduced mitochondrial membrane potential induced by rotenone treatment and reinstate rotenone-induced increases in catalase, glutathione peroxidase, and superoxide dismutase activities. All the extracts inhibited rotenone-induced changes in nuclear morphology and DNA condensation, an early event of cellular apoptosis. LC-QTOF-MS analysis of the plant extracts shows the presence of neuroprotective compounds. CONCLUSIONS: The plant extracts showed neuroprotective activities against rotenone-treated SH-SY5Y cells through antioxidant and anti-apoptotic mechanisms. These findings support the ethnopharmacological uses of these plants in treating neurological disorders. They probably are a good source of neuroprotective compounds that could be further explored to develop treatment strategies for neurodegenerative diseases like Parkinson's disease.

Drug addiction and treatment: An epigenetic perspective.

Drug addiction is a complex disease affected by numerous genetic and environmental factors. Brain regions in reward pathway, neuronal adaptations, genetic and epigenetic interactions causing transcriptional enhancement or repression of multiple genes induce different addiction phenotypes for varying duration. Addictive drug use causes epigenetic alterations and similarly epigenetic changes induced by environment can promote addiction. Epigenetic mechanisms include DNA methylation and post-translational modifications like methylation, acetylation, phosphorylation, ubiquitylation, sumoylation, dopaminylation and crotonylation of histones, and ADP-ribosylation. Non-coding RNAs also induce epigenetic changes. This review discusses these above areas and stresses the need for exploring epidrugs as a treatment alternative and adjunct, considering the limited success of current addiction treatment strategies. Epigenome editing complexes have lately been effective in eukaryotic systems. Targeted DNA cleavage techniques such as CRISPR-Cas9 system, CRISPR-dCas9 complexes, transcription activator-like effector nucleases (TALENs) and zinc-finger nucleases (ZFNs) have been exploited as targeted DNA recognition or anchoring platforms, fused with epigenetic writer or eraser proteins and delivered by transfection or transduction methods. Efficacy of epidrugs is seen in various neuropsychiatric conditions and initial results in addiction treatment involving model organisms are remarkable. Epidrugs present a promising alternative treatment for addiction.

Structural and Functional Diversity of the Peroxiredoxin 6 Enzyme Family.

Significance: Peroxiredoxins (Prdxs) with a single peroxidative cysteine (CP) in a conserved motif PXXX(T/S)XXCP within its thioredoxin fold, have been classified as the peroxiredoxin 6 (Prdx6 ) family. All Prdxs can reduce H2O2 and short chain hydroperoxides while Prdx6 in addition, can reduce phospholipid hydroperoxides (PLOOH) due to its ability to interact with peroxidized phospholipid substrate. The single CP of Prdx6 uses various external electron donors including glutathione thioredoxin, and ascorbic acid for resolution of its peroxidized state and, therefore, its peroxidase activity. Prdx6 proteins also exhibit Ca2+-independent phospholipase A2 (PLA2), lysophosphatidylcholine acyltransferase (LPCAT), and chaperone activities that depend on cellular localization and the oxidation and oligomerisation states of the protein. Thus, Prdx6 is a "moonlighting" enzyme. Recent Advance: Physiologically, Prdx6s have been reported to play an important role in protection against oxidative stress, repair of peroxidized cell membranes, mammalian lung surfactant turnover, activation of some NADPH oxidases, the regulation of seed germination in plants, as an indicator of cellular levels of reactive O2 species through Nrf-Klf9 activation, and possibly in male fertility, regulation of cell death through ferroptosis, cancer metastasis, and oxidative stress-related signalling pathways. Critical Issues: This review outlines Prdx6 enzyme unique structural features and explores its wide range of physiological functions. Yet, existing structural data falls short of fully revealing all of human Prdx6 multifunctional roles. Further endeavour is required to bridge this gap in its understanding. Although there are wide variations in both the structure and function of Prdx6 family members in various organisms, all Prdx6 proteins show the unique a long C-terminal extension that is also seen in Prdx1, but not in other Prdxs. Future Directions: As research data continues to accumulate, the potential for detailed insights into the role of C-terminal of Prdx6 in its oligomerisation and activities. There is a need for thorough exploration of structural characteristics of the various biological functions. Additionally, uncovering the interacting partners of Prdx6 and understanding its involvement in signalling pathways will significantly contribute to a more profound comprehension of its role.

Polymorphisms in drug metabolism genes as a risk factor for first-line anti-tuberculosis drug-induced liver injury.

BACKGROUND: Anti-tuberculosis drug-induced liver injury (AT-DILI) is one of the most common side effects in TB patients during treatment. The prime cause of liver injury during TB treatment is reported to be isoniazid and its metabolites. Different factors influenced the development of AT-DILI, and genetic factors are one of the major factors. METHODS AND RESULTS: Polymorphisms in drug metabolism genes like NAT2, CYP2E1, PXR, and GST have been reported to be associated with AT-DILI, and they are one of the major areas of focus at present. Attempts are met in this review to analyse the different markers in these drug metabolism genes for their association with AT-DILI. CONCLUSION: A better understanding of the polymorphisms in these genes and their functional effects will give better insights into the development of AT-DILI, and it could facilitate in designing and developing more effective personalized treatment for TB.

Association of Dopamine Transporter Gene with Heroin Dependence in an Indian Subpopulation from Manipur.

Dopamine transporter (DAT) or solute carrier family 6 member 3 (SLC6A3) is a transmembrane protein regulating dopaminergic neurotransmission. It has been implicated in playing important roles in the dopaminergic reward pathways, and thus, DAT1 is a strong candidate gene for association studies with heroin dependence. A case-control study involving 279 individuals (147 controls and 132 heroin-dependent cases) was conducted. Ten polymorphisms of the DAT1 (SLC6A3) gene were analysed for its association with heroin dependence. Following the Hardy-Weinberg equilibrium (HWE) test, genetic association analyses were performed for the study groups. The post hoc statistical power of the study was 0.655 (65.5%). Single-nucleotide polymorphism (SNP) rs246997 was found to be significantly associated with heroin dependence at allelic, genotypic, and haplotypic levels. A significant difference in the distribution of 11R allele and 10R/11R genotype of rs28363170 between heroin-dependent cases and controls was also observed. Nominal significance at degrees of freedom (df) = 5 was also observed for rs28363170. Five bimarker-based haplotype combinations were also found to be associated with heroin dependence. For the first time, 13R allele (7R/13R genotype) and 14R allele (7R/14R genotype) were identified for rs3836790 in the population. The study also reports that the 11R allele and 10R/11R genotype of rs28363170 is associated with protection against heroin dependence. 7R and 6R alleles were also found to be the common alleles of rs3836790 in the study population. The study provides evidence for the association of polymorphisms of DAT1 (SLC6A3) with heroin dependence.

A single nucleotide polymorphism in OPRM1(rs483481) and risk for heroin use disorder.

Opioid receptor mu1 (OPRM1) is the target of many opioid drugs, and it is known to have affinity toward both endogenous and exogenous opioids, opiate and opioid analgesic drugs. The present study was undertaken to explore association of single nucleotide polymorphisms (SNPs) in the OPRM1 gene with heroin use disorder. Ten OPRM1 polymorphisms were analyzed in 132 cases and 147 healthy controls. The SNP rs483481 showed significant allelic, genotypic and haplotypic association (Allelic: p-value = 0.003, OR = 1.75, CI = 1.21-2.55) (Genotypic: p-value = 0.003, OR = 1.72, CI = 1.08-2.75) with heroin use disorder. Allelic and genotypic association remained significant even after multiple testing corrections with 1000 permutations. A significant positive correlation between 'Number of times drug abstained' and 'rs483481-AA genotype' (p-value = 0.002; Pearson correlation = 0.265) was also observed. One-way ANOVA analysis demonstrated significant association of rs483481 with 'number of times drug abstained' (F = 4.86, p-value =0.009). 'A' allele and 'AA' genotype of marker rs483481 seem to confer protective effect while 'G' allele and 'GG' genotype potentiates risk for heroin use disorder. OPRM1 is found to be associated with heroin use disorder in the studied Manipuri cohort. The study suggests that individuals with G allele and GG genotypes at rs483481 could be more vulnerable to heroin dependence, and it could be taken into consideration in prevention and intervention programs.

Embryonic stem cells derived neuron transplantation recovery in models of parkinsonism in relation to severity of the disorder in rats.

6-Hydroxydopamine (6-OHDA)- and 1-methyl-4-phenylpyridinium (MPP(+))-induced hemi-parkinsonism was investigated in relation to the severity of the disorder in terms of behavioral disability and nigral neuronal loss and recovery regarding the number of stem cell-derived neurons transplanted in the striatum. Intra-median forebrain bundle infusion of the parkinsonian neurotoxins and intra-striatal transplantation of differentiated embryonic stem cells (ESCs) were carried out by rat brain stereotaxic surgery. The severity of the disease was determined using the number of amphetamine- or apomorphine-induced rotations, striatal dopamine levels as estimated by high-performance liquid chromatography (HPLC)-electrochemistry, and the number of surviving tyrosine hydroxylase immunoreactive dopaminergic neurons in the substantia nigra pars compacta. Rats that received unilateral infusion of 6-OHDA or MPP(+) responded with dose-dependent, unilateral bias in turning behavior when amphetamine or apomorphine was administered. Rotational asymmetry in both models correlated significantly well with the loss in the number of nigral dopaminergic neurons and striatal dopamine depletion. Transplantation of 2×10(5) differentiated murine ESCs revealed remarkably similar kinds of recovery in both animal models. The survival of the grafted dopaminergic cells in the striatum was better in animals with low-severity parkinsonism, but poor in the animals with severe parkinsonism. Amphetamine-induced rotational recovery correlated positively with an increasing number of cells transplanted in animals with uniform nigral neuronal lesion. These results suggest that disease severity is an important factor for determining the number of cells to be transplanted in parkinsonian rats for desirable recovery, which may be true in clinical conditions too.

Engraftment of mouse embryonic stem cells differentiated by default leads to neuroprotection, behaviour revival and astrogliosis in parkinsonian rats.

We report here protection against rotenone-induced behavioural dysfunction, striatal dopamine depletion and nigral neuronal loss, following intra-striatal transplantation of neurons differentiated from murine embryonic stem cells (mES). mES maintained in serum free medium exhibited increase in neuronal, and decrease in stem cell markers by 7th and 10th days as revealed by RT-PCR and immunoblot analyses. Tyrosine hydroxylase, NURR1, PITX3, LMX1b and c-RET mRNA showed a significant higher expression in differentiated cells than in mES. Dopamine level was increased by 3-fold on 10th day as compared to 7 days differentiated cells. Severity of rotenone-induced striatal dopamine loss was attenuated, and amphetamine-induced unilateral rotations were significantly reduced in animals transplanted with 7 days differentiated cells, but not in animals that received undifferentiated ES transplant. However, the ratio of contralateral to ipsilateral swings in elevated body swing test was significantly reduced in both the transplanted groups, as compared to control. Striatal grafts exhibited the presence of tyrosine hydroxylase positive cells, and the percentage of dopaminergic neurons in the substantia nigra was also found to be higher in the ipsilateral side of 7 days and mES grafted animals. Increased expression of CD11b and IBA-1, suggested a significant contribution of these microglia-derived factors in controlling the limited survival of the grafted cells. Astrocytosis in the grafted striatum, and significant increase in the levels of glial cell line derived neurotrophic factor may have contributed to the recovery observed in the hemiparkinsonian rats following transplantation.

Evidence for the involvement of central serotonergic mechanisms in cholinergic tremor induced by tacrine in Balb/c mice.

Tacrine is a potent and reversible inhibitor of acetylcholinesterase (AChE) in the brain. It produces tremor in animals, which is believed to be due to an increase in the brain acetylcholine level following AChE inhibition. The present study was undertaken to investigate the involvement, if any, of biogenic amines in the genesis of this motor dysfunction. Administration of tacrine (10-20 mg/kg, i.p.) produced dose- and time-dependent tremor in Balb/c mice. While in vivo inhibition of striatal AChE activity was observed only for the highest dose of tacrine, a dose-dependent increase in striatal choline acetyltransferase activity was obtained. Serotonin (5-HT) levels, as assayed following a sensitive HPLC-electrochemical procedure, were significantly increased in nucleus caudatus putamen, nucleus accumbens, substantia nigra, nucleus raphe dorsalis, olivary nucleus and the cerebellum. However, dopamine or norepinephrine levels remained unaltered in these areas of the brain. In animals treated with p-chlorophenylalanine, a specific tryptophan hydroxylase inhibitor and 5-HT depletor, tacrine failed to elevate the levels of 5-HT in the brain regions, and significantly attenuated tremor response to the drug. Tacrine-induced tremor was also significantly (83%) attenuated by 5-HT(2A/2C) receptor antagonist mianserin (5 mg/kg, i.p.), but methysergide (5 mg/kg, i.v.) could block tacrine-induced tremor only by 20%. Atropine (5 mg/kg, i.p.) antagonized tacrine-induced tremor by about 53%, but a combination of atropine and mianserin completely blocked the tremor response. These results indicate that the cholinergic tremor produced by tacrine in Balb/c mice is mediated via central serotonergic mechanisms, and stimulation of 5-HT(2A/2C) receptors plays a pivotal role in this motor dysfunction.

Swim-test as a function of motor impairment in MPTP model of Parkinson's disease: a comparative study in two mouse strains.

Parkinson's disease (PD) is a common neurodegenerative disease that exhibits motor dysfunctions, such as tremor, akinesia and rigidity. In the present study, we investigated whether swim-test could be used as one of the behavioural monitoring techniques to study motor disability in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism in two mouse strains, Balb/c and C57BL/6. Mice were treated with different doses of MPTP (10, 20 and 30 mg/kg, twice, 16 h apart), and were subjected to swim-test on the third day of the first MPTP injection. MPTP-induced tremor was monitored at 30 min, and akinesia and rigidity developed were studied 3 h after the second MPTP treatment. While tremor and akinesia produced were dose-dependent and the intensity of tremor was comparable in the two strains of mice studied, the latter response in C57BL/6 was significantly lesser than that observed in Balb/c. Rigidity exhibited in Balb/c mice were dose-dependent, but not in C57BL/6. There was observed an inverse relationship between swim-score and the doses of MPTP in both the strains. MPTP caused a significant and dose-dependent reduction in striatal dopamine level in both the strains of mice, when assayed on the fourth day employing an HPLC with electrochemical detector. A significant positive correlation existed (r = 0.94 for Balb/c and r = 0.82 for C57BL/6) for the striatal dopamine-depletion and the swim-score in the MPTP-treated mice. While swim deficit and striatal dopamine loss were long lasting (till the third week) in C57BL/6, in Balb/c mice the motor deficit showed recovery by the second week. In these animals, a significant attenuation in striatal dopamine loss was observed by the third week. These results indicate that swim ability is directly proportional to striatal dopamine content, and suggest that swim-test could be used as a major technique to monitor motor dysfunction in experimental animals.