Cdk5-mediated oligodendrocyte myelin breakdown and neuroinflammation: Implications for the link between Type 2 Diabetes and Alzheimer's disease.

Oligodendrocytes, crucial myelinating glia in the central nervous system, play a vital role in maintaining axonal integrity and facilitating efficient nerve impulse conduction. The degradation of myelin in oligodendrocytes has been implicated in Alzheimer's disease (AD) and cognitive dysfunction. Interestingly, individuals with Type 2 Diabetes (T2D) have a significantly higher likelihood of developing cognitive impairment, possibly due to insulin resistance and glucose toxicity within the central nervous system (CNS). However, the precise relationship between these two disorders remains elusive. Our study proposes a potential link between T2D and AD, involving Cdk5-mediated breakdown of oligodendrocyte myelin and neuroinflammation. In the context of T2D, glucose toxicity in oligodendrocytes leads to heightened Cdk5 kinase activity and cPLA2 hyperactivation, resulting in chronic inflammation and myelin deterioration. This myelin breakdown in oligodendrocytes is thought to contribute to the development of AD and cognitive dysfunction. Notably, the administration of a Cdk5 inhibitor (TFP5) effectively alleviates neuroinflammation and myelin degradation. Moreover, our findings demonstrate heightened activity of Cdk5, cPLA2, and phospho-cPLA2 levels in the brain of a mouse model with Type 2 Diabetes (T2D). Hence, our findings suggest that targeting Cdk5 could be a promising therapeutic strategy to counteract AD pathogenesis in T2D-related conditions.

Pallidal Deep Brain Stimulation for KMT2B Related Dystonia in An Indian Patient.

Outcomes of pallidal stimulation in KMT2B dystonia have been infrequently reported prospectively. We report the six-month outcomes of bilateral GPi DBS in an Asian Indian patient with early-onset generalized dystonia associated with a novel heterozygous variant in the KMT2B gene.

ATP7A Clinical Genetics Resource - A comprehensive clinically annotated database and resource for genetic variants in ATP7A gene.

ATP7A is a critical copper transporter involved in Menkes Disease, Occipital horn Syndrome and X-linked distal spinal muscular atrophy type 3 which are X linked genetic disorders. These are rare diseases and their genetic epidemiology of the diseases is unknown. A number of genetic variants in the genes have been reported in published literature as well as databases, however, understanding the pathogenicity of variants and genetic epidemiology requires the data to be compiled in a unified format. To this end, we systematically compiled genetic variants from published literature and datasets. Each of the variants were systematically evaluated for evidences with respect to their pathogenicity and classified as per the American College of Medical Genetics and the Association of Molecular Pathologists (ACMG-AMP) guidelines into Pathogenic, Likely Pathogenic, Benign, Likely Benign and Variants of Uncertain Significance. Additional integrative analysis of population genomic datasets provides insights into the genetic epidemiology of the disease through estimation of carrier frequencies in global populations. To deliver a mechanistic explanation for the pathogenicity of selected variants, we also performed molecular modeling studies. Our modeling studies concluded that the small structural distortions observed in the local structures of the protein may lead to the destabilization of the global structure. To the best of our knowledge, ATP7A Clinical Genetics Resource is one of the most comprehensive compendium of variants in the gene providing clinically relevant annotations in gene.

Crosstalk Between the Unfolded Protein Response, MicroRNAs, and Insulin Signaling Pathways: In Search of Biomarkers for the Diagnosis and Treatment of Type 2 Diabetes.

Type 2 diabetes mellitus (T2DM) is a metabolic disorder that is characterized by functional defects in glucose metabolism and insulin secretion. Its complex etiology and multifaceted nature have made it difficult to design effective therapies for early diagnosis and treatment. Several lines of evidence indicate that aberrant activation of the unfolded protein response (UPR) in response to endoplasmic reticulum (ER) stress impairs the ß cell's ability to respond to glucose and promotes apoptosis. Elucidating the molecular mechanisms that govern ß cell dysfunction and cell death can help investigators design therapies to halt or prevent the development of T2DM. Early diagnosis of T2DM, however, warrants additionally the identification of potential biomarkers. MicroRNAs (miRNAs) are key regulators of transcriptional processes that modulate various features of insulin signaling, such as insulin sensitivity, glucose tolerance, and insulin secretion. A deeper understanding of how changes in patterns of expression of miRNAs correlate with altered glucose metabolism can enable investigators to develop methods for the early diagnosis and treatment of T2DM. The first part of this review examines how altered expression of specific UPR pathway proteins disrupts ER function and causes ß cell dysfunction, while the second part discusses the potential role of miRNAs in the diagnostic and treatment of T2DM.

Phosphorylation of the Transient Receptor Potential Ankyrin 1 by Cyclin-dependent Kinase 5 affects Chemo-nociception.

Cyclin-dependent kinase 5 (Cdk5) is a key neuronal kinase that is upregulated during inflammation, and can subsequently modulate sensitivity to nociceptive stimuli. We conducted an in silico screen for Cdk5 phosphorylation sites within proteins whose expression was enriched in nociceptors and identified the chemo-responsive ion channel Transient Receptor Potential Ankyrin 1 (TRPA1) as a possible Cdk5 substrate. Immunoprecipitated full length TRPA1 was shown to be phosphorylated by Cdk5 and this interaction was blocked by TFP5, an inhibitor that prevents activation of Cdk5. In vitro peptide-based kinase assay revealed that four of six TRPA1 Cdk5 consensus sites acted as substrates for Cdk5, and modeling of the ankyrin repeats disclosed that phosphorylation would occur at characteristic pockets within the (T/S)PLH motifs. Calcium imaging of trigeminal ganglion neurons from genetically engineered mice overexpressing or lacking the Cdk5 activator p35 displayed increased or decreased responsiveness, respectively, to stimulation with the TRPA1 agonist allylisothiocyanate (AITC). AITC-induced chemo-nociceptive behavior was also heightened in vivo in mice overexpressing p35 while being reduced in p35 knockout mice. Our findings demonstrate that TRPA1 is a substrate of Cdk5 and that Cdk5 activity is also able to modulate TRPA1 agonist-induced calcium influx and chemo-nociceptive behavioral responses.

Peripheral and orofacial pain sensation is unaffected by the loss of p39.

Abstract: Cdk5 is a key neuronal kinase necessary for proper brain development, which has recently been implicated in modulating nociception. Conditional deletion of Cdk5 in pain-sensing neurons attenuates pain responses to heat in both the periphery and orofacial regions. Cdk5 activity is regulated by binding to the activators p35 and p39, both of which possess a cyclin box. Our previous examination of the nociceptive role of the well-characterized Cdk5 activator p35 using mice that either lack or overexpress this regulatory subunit demonstrated that Cdk5/p35 activity affects mechanical, chemical, and thermal nociception. In contrast, the nociceptive role of Cdk5's other less-studied activator p39 is unknown. Here, we report that the knockout of p39 in mice did not affect orofacial and peripheral nociception. The lack of any algesic response to nociceptive stimuli in the p39 knockout mice contrasts with the hypoalgesic effects that result from the deletion of p35. Our data demonstrate different and nonoverlapping roles of Cdk5 activators in the regulation of orofacial as well as peripheral nociception with a crucial role for Cdk5/p35 in pain signaling.

TFP5, a Peptide Inhibitor of Aberrant and Hyperactive Cdk5/p25, Attenuates Pathological Phenotypes and Restores Synaptic Function in CK-p25Tg Mice.

It has been reported that cyclin-dependent kinase 5 (cdk5), a critical neuronal kinase, is hyperactivated in Alzheimer's disease (AD) and may be, in part, responsible for the hallmark pathology of amyloid plaques and neurofibrillary tangles (NFTs). It has been proposed by several laboratories that hyperactive cdk5 results from the overexpression of p25 (a truncated fragment of p35, the normal cdk5 regulator), which, when complexed to cdk5, induces hyperactivity, hyperphosphorylated tau/NFTs, amyloid-ß plaques, and neuronal death. It has previously been shown that intraperitoneal (i.p.) injections of a modified truncated 24-aa peptide (TFP5), derived from the cdk5 activator p35, penetrated the blood-brain barrier and significantly rescued AD-like pathology in 5XFAD model mice. The principal pathology in the 5XFAD mutant, however, is extensive amyloid plaques; hence, as a proof of concept, we believe it is essential to demonstrate the peptide's efficacy in a mouse model expressing high levels of p25, such as the inducible CK-p25Tg model mouse that overexpresses p25 in CamKII positive neurons. Using a modified TFP5 treatment, here we show that peptide i.p. injections in these mice decrease cdk5 hyperactivity, tau, neurofilament-M/H hyperphosphorylation, and restore synaptic function and behavior (i.e., spatial working memory, motor deficit using Rota-rod). It is noteworthy that TFP5 does not inhibit endogenous cdk5/p35 activity, nor other cdks in vivo suggesting it might have no toxic side effects, and may serve as an excellent therapeutic candidate for neurodegenerative disorders expressing abnormally high brain levels of p25 and hyperactive cdk5.

Profiling of p5, a 24 Amino Acid Inhibitory Peptide Derived from the CDK5 Activator, p35 CDKR1 Against 70 Protein Kinases.

Cyclin-dependent kinase 5 (CDK5) is a multifunctional serine/threonine kinase that regulates a large number of neuronal processes essential for nervous system development and function with its activator p35 CDK5R1. Upon neuronal insults, p35 is proteolyzed and cleaved to p25 producing deregulation and hyperactivation of CDK5 (CDK5/p25), implicated in tau hyperphosphorylation, a pathology in some neurodegenerative diseases. A truncated, 24 amino acid peptide, p5, derived from p35 inhibits the deregulated CDK5 phosphotransferase activity and ameliorates Alzheimer's disease (AD) phenotypes in AD model mice. In the present study, we have screened a diverse panel of 70 human protein kinases for their sensitivities to p5, and a subset of these to p35. At least 16 of the tested protein kinases exhibited IC50 values that were 250 µM or less, with CAMK4, ZAP70, SGK1, and PIM1 showing greater sensitivity to inhibition by p5 than CDK5/p35 and CDK5/p25. In contrast, the p5 peptide modestly activated LKB1 and GSK3ß. A sub set of kinases screened against p35 showed that activity of CAMK4 in the absence of calcium and calmodulin was also markedly inhibited by p35. The Cyclin Y-dependent kinases PFTK1 (CDK14) and PCTK1 (CDK16) were activated by p35 at least 10-fold in the absence of Cyclin Y and by approximately 50% in its presence. These findings provide additional insights into the mechanisms of action for p5 and p35 in the regulation of protein phosphorylation in the nervous system.

TFP5/TP5 peptide provides neuroprotection in the MPTP model of Parkinson's disease.

Cyclin-dependent kinase 5 (Cdk5) is a member of the serine-threonine kinase family of cyclin-dependent kinases. Cdk5 is critical to normal mammalian nervous system development and plays important regulatory roles in multiple cellular functions. Recent evidence indicates that Cdk5 is inappropriately activated in several neurodegenerative conditions, including Parkinson's disease (PD). PD is a chronic neurodegenerative disorder characterized by the loss of dopamine neurons in the substantia nigra, decreased striatal dopamine levels, and consequent extrapyramidal motor dysfunction. During neurotoxicity, p35 is cleaved to form p25. Binding of p25 with Cdk5 leads deregulation of Cdk5 resulting in number of neurodegenerative pathologies. To date, strategies to specifically inhibit Cdk5 hyperactivity have not been successful without affecting normal Cdk5 activity. Here we show that inhibition of p25/Cdk5 hyperactivation through TFP5/TP5, truncated 24-aa peptide derived from the Cdk5 activator p35 rescues nigrostriatal dopaminergic neurodegeneration induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP/MPP(+)) in a mouse model of PD. TP5 peptide treatment also blocked dopamine depletion in the striatum and improved gait dysfunction after MPTP administration. The neuroprotective effect of TFP5/TP5 peptide is also associated with marked reduction in neuroinflammation and apoptosis. Here we show inhibition of Cdk5/p25-hyperactivation by TFP5/TP5 peptide, which identifies Cdk5/p25 as a potential therapeutic target to reduce neurodegeneration in PD.

Analysis of the Inhibitory Elements in the p5 Peptide Fragment of the CDK5 Activator, p35, CDKR1 Protein.

Besides the hallmark pathology of amyloid plaques and neurofibrillary tangles, it is well documented that cyclin-dependent kinase 5 (CDK5), a critical neuronal protein kinase in nervous system development, function, and survival, when deregulated and hyperactivated induces Alzheimer's disease (AD) and amyotrophic lateral sclerosis and Parkinson's disease-like phenotypes in mice. In a recent study, we demonstrated that p5, a small, truncated fragment of 24 amino acid residues derived from the CDK5 activator protein 35 (NCK5A, p35), selectively inhibited deregulated CDK5 hyperactivity and ameliorated AD phenotypes in model mice. In this study, we identified the most inhibitory elements in the p5 peptide fragment. Each amino acid residue in p5 was systematically replaced with its homologous residues that may still be able to functionally substitute. The effects of these p5 peptide analogs were studied on the phosphotransferase activities of CDK5/p35, CDK5/p25, ERK1, and GSK3ß. The mimetic p5 peptide (A/V substitution at the C-terminus of the peptide) in the sequence, KNAFYERALSIINLMTSKMVQINV (p5-MT) was the most effective inhibitor of CDK5 kinase activity of 79 tested mimetic peptides including the original p5 peptide, KEAFWDRCLSVINLMSSKMLQINA (p5-WT). Replacement of the residues in C-terminus end of the peptide affected CDK5 phosphotransferase activity most significantly. These peptides were strong inhibitors of CDK5, but not the related proline-directed kinases, ERK1 and GSK3ß.

Peptide TFP5/TP5 derived from Cdk5 activator P35 provides neuroprotection in the MPTP model of Parkinson's disease.

Parkinson's disease (PD) is a chronic neurodegenerative disorder characterized by the loss of dopamine neurons in the substantia nigra, decreased striatal dopamine levels, and consequent extrapyramidal motor dysfunction. Recent evidence indicates that cyclin-dependent kinase 5 (Cdk5) is inappropriately activated in several neurodegenerative conditions, including PD. To date, strategies to specifically inhibit Cdk5 hyperactivity have not been successful without affecting normal Cdk5 activity. Previously we reported that TFP5 peptide has neuroprotective effects in animal models of Alzheimer's disease. Here we show that TFP5/TP5 selective inhibition of Cdk5/p25 hyperactivation in vivo and in vitro rescues nigrostriatal dopaminergic neurodegeneration induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP/MPP+) in a mouse model of PD. TP5 peptide treatment also blocked dopamine depletion in the striatum and improved gait dysfunction after MPTP administration. The neuroprotective effect of TFP5/TP5 peptide is also associated with marked reduction in neuroinflammation and apoptosis. Here we show selective inhibition of Cdk5/p25 -hyperactivation by TFP5/TP5 peptide, which identifies the kinase as a potential therapeutic target to reduce neurodegeneration in Parkinson's disease.

TFP5, a peptide derived from p35, a Cdk5 neuronal activator, rescues cortical neurons from glucose toxicity.

Multiple lines of evidence link the incidence of diabetes to the development of Alzheimer's disease (AD). Patients with diabetes have a 50 to 75% increased risk of developing AD. Cyclin dependent kinase 5 (Cdk5) is a serine/threonine protein kinase, which forms active complexes with p35 or p39, found principally in neurons and in pancreatic ß cells. Recent studies suggest that Cdk5 hyperactivity is a possible link between neuropathology seen in AD and diabetes. Previously, we identified P5, a truncated 24-aa peptide derived from the Cdk5 activator p35, later modified as TFP5, so as to penetrate the blood-brain barrier after intraperitoneal injections in AD model mice. This treatment inhibited abnormal Cdk5 hyperactivity and significantly rescued AD pathology in these mice. The present study explores the potential of TFP5 peptide to rescue high glucose (HG)-mediated toxicity in rat embryonic cortical neurons. HG exposure leads to Cdk5-p25 hyperactivity and oxidative stress marked by increased reactive oxygen species production, and decreased glutathione levels and superoxide dismutase activity. It also induces hyperphosphorylation of tau, neuroinflammation as evident from the increased expression of inflammatory cytokines like TNF-α, IL-1ß, and IL-6, and apoptosis. Pretreatment of cortical neurons with TFP5 before HG exposure inhibited Cdk5-p25 hyperactivity and significantly attenuated oxidative stress by decreasing reactive oxygen species levels, while increasing superoxide dismutase activity and glutathione. Tau hyperphosphorylation, inflammation, and apoptosis induced by HG were also considerably reduced by pretreatment with TFP5. These results suggest that TFP5 peptide may be a novel candidate for type 2 diabetes therapy.

Topographic regulation of neuronal intermediate filaments by phosphorylation, role of peptidyl-prolyl isomerase 1: significance in neurodegeneration.

The neuronal cytoskeleton is tightly regulated by phosphorylation and dephosphorylation reactions mediated by numerous associated kinases, phosphatases and their regulators. Defects in the relative kinase and phosphatase activities and/or deregulation of compartment-specific phosphorylation result in neurodegenerative disorders. The largest family of cytoskeletal proteins in mammalian cells is the superfamily of intermediate filaments (IFs). The neurofilament (NF) proteins are the major IFs. Aggregated forms of hyperphosphorylated tau and phosphorylated NFs are found in pathological cell body accumulations in the central nervous system of patients suffering from Alzheimer's disease, Parkinson's disease, and Amyotrophic Lateral Sclerosis. The precise mechanisms for this compartment-specific phosphorylation of cytoskeletal proteins are not completely understood. In this review, we focus on the mechanisms of neurofilament phosphorylation in normal physiology and neurodegenerative diseases. We also address the recent breakthroughs in our understanding the role of different kinases and phosphatases involved in regulating the phosphorylation status of the NFs. In addition, special emphasis has been given to describe the role of phosphatases and Pin1 in phosphorylation of NFs.

siRNA against presenilin 1 (PS1) down regulates amyloid ß42 production in IMR-32 cells.

BACKGROUND: One of the pathological hallmarks of Alzheimer's disease (AD) is the deposition of the ~4 kDa amyloid ß protein (Aß) within lesions known as senile plaques. Aß is also deposited in the walls of cerebral blood vessels in many cases of AD. A substantial proportion of the Aß that accumulates in the AD brain is deposited as Amyloid, which is highly insoluble, proteinaceous material with a ß-pleated-sheet conformation and deposited extracellularly in the form of 5-10 nm wide straight fibrils. As γ-secretase catalyzes the final cleavage that releases the Aß42 or 40 from amyloid ß -protein precursor (APP), therefore, it is a potential therapeutic target for the treatment of AD. γ-Secretase cleavage is performed by a high molecular weight protein complex containing presenilins (PSs), nicastrin, Aph-1 and Pen-2. Previous studies have demonstrated that the presenilins (PS1 and PS2) are critical components of a large enzyme complex that performs γ-secretase cleavage. METHODS: In this study we used RNA interference (RNAi) technology to examine the effects of small-interfering RNA (siRNA) against PS1 on expression levels of PS1 and Aß42 in IMR-32 Cells using RTPCR, western blotting and immunofluorescence techniques. RESULTS: The results of the present study showed down regulation of PS1 and Aß42 in IMR32 cells transfected with siRNA against PS1. CONCLUSION: Our results substantiate the concept that PS1 is involved in γ-secretase activity and provides the rationale for therapeutic strategies aimed at influencing Aß42 production.

Protective efficacy of coenzyme Q10 against DDVP-induced cognitive impairments and neurodegeneration in rats.

The present study was carried out to elucidate the effects of coenzyme Q(10) (CoQ(10)) against cognitive impairments induced by dichlorvos (DDVP). We have previously shown organophosphate, DDVP-induced impairments in neurobehavioral indices viz. rota rod, passive avoidance, and water maze tests. In addition to this, we have also reported that chronic DDVP exposure leads to decreased mitochondrial electron transfer activities of cytochrome oxidase along with altered mitochondrial complexes I-III activity. Administration of CoQ(10) (4.5 mg/kg, i.p. for 12 weeks prior to DDVP administration daily) to DDVP-treated rats improved cognitive performance in passive avoidance task and Morris water maze test. Furthermore, CoQ(10) treatment also reduced oxidative stress (as evident by reduced malondialdehyde, decreased ROS and increased Mn-SOD activity) in DDVP-treated rats' hippocampus region, along with enhanced activity of complexes I-III and complex IV. Electron microscope studies of rat hippocampus mitochondria revealed that CoQ(10) administration leads to near normal physiology of mitochondria with well-defined cristae compared with DDVP-treated animals where enlarged mitochondria with distorted cristae are observed. CoQ(10) administration also attenuated neuronal damage in hippocampus as evident from histopathological studies. These results demonstrate the beneficial effects of CoQ(10) against organophosphate-induced cognitive impairments and hippocampal neuronal degeneration.

Chronic dichlorvos exposure: microglial activation, proinflammatory cytokines and damage to nigrostriatal dopaminergic system.

Dopaminergic cells in the substantia nigra are highly vulnerable to the neurodegenerative process of Parkinson's disease. Therefore, mechanisms that enhance their susceptibility to injury bear important implications for disease pathogenesis. We have previously shown that chronic dichlorvos exposure caused nigrostriatal dopaminergic degeneration and significant behavioral impairments. In this study, we analyzed the relationship between microglial activation and dopaminergic neurodegeneration to examine the possibility that neuroinflammation may induce dopaminergic neuronal loss in the nigrostriatal system. Chronic dichlorvos exposure causes microglial activation including induction of NADPH oxidase and a selective loss of dopaminergic neurons in rat. Microglial marker expression was increased at transcription as well as translational levels in the substantia nigra (SN) and corpus striatum (CS) of rats exposed to dichlorvos. Activated microglia were seen in SN and CS of dichlorvos-treated animals but were rarely observed in controls. Immunostaining revealed lesser number of TH-positive neurons and higher number of microglia in SN and CS regions after dichlorvos treatment. The mRNA and protein levels of the NADPH oxidase main subunit gp91(phox) were significantly increased after dichlorvos administration. Dichlorvos exposure also leads to increased level of microglial noxious mediators such as IL-1ß, TNF-α and IL-6 in ventral midbrain and CS at transcription as well as translational levels. Data indicate that microglial activation and consequent induction of NADPH oxidase and proinflammatory cytokines such as TNF-α, IL-1ß and IL-6 may act as risk factors for Parkinson's disease by increasing the vulnerability of dopaminergic cells to dichlorvos toxic injury.

Protection of dichlorvos induced oxidative stress and nigrostriatal neuronal death by chronic coenzyme Q10 pretreatment.

Numerous epidemiological studies have shown an association between pesticide exposure and increased risk of developing Parkinson's diseases. Oxidative stress generated as a result of mitochondrial dysfunction has been implicated as an important factor in the etiology of Parkinson's disease. Previously, we reported that chronic dichlorvos exposure causes mitochondrial impairments and nigrostriatal neuronal death in rats. The present study was designed to test whether Coenzyme Q(10) (CoQ(10)) administration has any neuroprotective effect against dichlorvos mediated nigrostriatal neuronal death, α-synuclein aggregation, and motor dysfunction. Male albino rats were administered dichlorvos by subcutaneous injection at a dose of 2.5 mg/kg body weight over a period of 12 weeks. Results obtained there after showed that dichlorvos exposure leads to enhanced mitochondrial ROS production, α-synuclein aggregation, decreased dopamine and its metabolite levels resulting in nigrostriatal neurodegeneration. Pretreatment by Coenzyme Q(10) (4.5 mg/kg ip for 12 weeks) to dichlorvos treated animals significantly attenuated the extent of nigrostriatal neuronal damage, in terms of decreased ROS production, increased dopamine and its metabolite levels, and restoration of motor dysfunction when compared to dichlorvos treated animals. Thus, the present study shows that Coenzyme Q(10) administration may attenuate dichlorvos induced nigrostriatal neurodegeneration, α-synuclein aggregation and motor dysfunction by virtue of its antioxidant action.

Serum paraoxonase-1 (PON1) activities (PONase/AREase) and polymorphisms in patients with type 2 diabetes mellitus in a North-West Indian population.

OBJECTIVE: Paraoxonase-1 (PON1), an HDL-C associated enzyme, protects lipoproteins from oxidation. There is evidence that PON1 enzyme activity is reduced in the patients with type 2 diabetes mellitus (T2DM). North-West Indian Punjabis, a distinct ethnic group has high incidence of T2DM. However till date there is no information regarding PON1 enzyme activities and PON1 polymorphisms in T2DM patients of this ethnic group. METHODS: We identified polymorphisms in the coding Q192R, L55M and promoter -909G/C, -162A/G, -108C/T of the PON1 gene by using PCR-RFLP, multiplex PCR and allele specific oligonucleotide PCR assays in 250 T2DM patients and 300 healthy controls. We also assessed paraoxonase (PONase) and arylesterase (AREase) activities of PON1 enzyme. RESULTS: The serum PONase (114.2 vs. 178.0nmol/min/ml) and AREase (62.7 vs. 82.5µmol/min/ml) activities were significantly lower (p<0.0001) in patients as compared to controls. PONase activity was affected by all the studied PON1 polymorphisms. However, AREase activity was not affected by any of these polymorphisms. Coding Q192R and promoter -909G/C polymorphisms showed significant differences in genotypic distribution. QR, RR (Q192R) and GC, CC (-909G/C) genotypes and L-C-A-R-G, L-T-A-R-G, L-T-G-Q-C haplotypes showed significant association with type 2 diabetes. No significant linkage disequilibrium was observed among the five polymorphisms. CONCLUSION: Both PONase and AREase activities are lower in patients and this could lead to increased lipid peroxidation and accelerated atherosclerosis in them. PONase activity, but not AREase activity is influenced by PON1 polymorphisms. QR, RR, GC, CC genotypes and L-C-A-R-G, L-T-A-R-G, L-T-G-Q-C haplotypes are commoner in diabetics as compared to controls and may be related to genetic susceptibility to type 2 diabetes.

Aluminum phosphide poisoning: an unsolved riddle.

Aluminum phosphide (ALP), a widely used insecticide and rodenticide, is also infamous for the mortality and morbidity it causes in ALP-poisoned individuals. The toxicity of metal phosphides is due to phosphine liberated when ingested phosphides come into contact with gut fluids. ALP poisoning is lethal, having a mortality rate in excess of 70%. Circulatory failure and severe hypotension are common features of ALP poisoning and frequent cause of death. Severe poisoning also has the potential to induce multi-organ failure. The exact site or mechanism of its action has not been proved in humans. Rather than targeting a single organ to cause gross damage, ALP seems to work at the cellular level, resulting in widespread damage leading to multiorgan dysfunction (MOD) and death. There has been proof in vitro that phosphine inhibits cytochrome c oxidase. However, it is unlikely that this interaction is the primary cause of its toxicity. Mitochondria could be the possible site of maximum damage in ALP poisoning, resulting in low ATP production followed by metabolic shutdown and MOD; also, owing to impairment in electron flow, there could be free radical generation and damage, again producing MOD. Evidence of reactive oxygen species-induced toxicity owing to ALP has been observed in insects and rats. A similar mechanism could also play a role in humans and contribute to the missing link in the pathogenesis of ALP toxicity. There is no specific antidote for ALP poisoning and supportive measures are all that are currently available.

MiADMSA reverses impaired mitochondrial energy metabolism and neuronal apoptotic cell death after arsenic exposure in rats.

Arsenicosis, due to contaminated drinking water, is a serious health hazard in terms of morbidity and mortality. Arsenic induced free radicals generated are known to cause cellular apoptosis through mitochondrial driven pathway. In the present study, we investigated the effect of arsenic interactions with various complexes of the electron transport chain and attempted to evaluate if there was any complex preference of arsenic that could trigger apoptosis. We also evaluated if chelation with monoisoamyl dimercaptosuccinic acid (MiADMSA) could reverse these detrimental effects. Our results indicate that arsenic exposure induced free radical generation in rat neuronal cells, which diminished mitochondrial potential and enzyme activities of all the complexes of the electron transport chain. Moreover, these complexes showed differential responses towards arsenic. These early events along with diminished ATP levels could be co-related with the later events of cytosolic migration of cytochrome c, altered bax/bcl(2) ratio, and increased caspase 3 activity. Although MiADMSA could reverse most of these arsenic-induced altered variables to various extents, DNA damage remained unaffected. Our study for the first time demonstrates the differential effect of arsenic on the complexes leading to deficits in bioenergetics leading to apoptosis in rat brain. However, more in depth studies are warranted for better understanding of arsenic interactions with the mitochondria.