The p75 neurotrophin receptor evades the endolysosomal route in neuronal cells, favouring multivesicular bodies specialised for exosomal release.

The p75 neurotrophin receptor (p75, also known as NGFR) is a multifaceted signalling receptor that regulates neuronal physiology, including neurite outgrowth, and survival and death decisions. A key cellular aspect regulating neurotrophin signalling is the intracellular trafficking of their receptors; however, the post-endocytic trafficking of p75 is poorly defined. We used sympathetic neurons and rat PC12 cells to study the mechanism of internalisation and post-endocytic trafficking of p75. We found that p75 internalisation depended on the clathrin adaptor protein AP2 and on dynamin. More surprisingly, p75 evaded the lysosomal route at the level of the early endosome, instead accumulating in two different types of endosomes, Rab11-positive endosomes and multivesicular bodies (MVBs) positive for CD63, a marker of the exosomal pathway. Consistently, depolarisation by KCl induced the liberation of previously endocytosed full-length p75 into the extracellular medium in exosomes. Thus, p75 defines a subpopulation of MVBs that does not mature to lysosomes and is available for exosomal release by neuronal cells.

INFANTILE ALEXANDER'S DISEASE: A CASE WITH CHARACTERISTIC MRI FEATURES.

Alexander disease, less commoniy known as fibrinoid leukodystrophy is an extremely rare, non- familial, progressive, lethal leukodystrophy which is characterized predominantly by abnormalities of white matter in bilateral frontal regions. It usually presents early within first 2 years of life with clinical features of macrocephaly, recurrent seizures and psychomotor retardation. Diagnosis of this white matter disorder is possible with certain features seen on magnetic resonance imaging (MRI), even without the need for histological confirmation. Our case is a one year old male infant who presented with repeated episodes of focal seizures to the paediatrician. He was referred for an MRI and subsequently based on typical MRI findings the diagnosis of Alexander disease was made.

Redox modification of Akt mediated by the dopaminergic neurotoxin MPTP, in mouse midbrain, leads to down-regulation of pAkt.

Impairment of Akt phosphorylation, a critical survival signal, has been implicated in the degeneration of dopaminergic neurons in Parkinson's disease. However, the mechanism underlying pAkt loss is unclear. In the current study, we demonstrate pAkt loss in ventral midbrain of mice treated with dopaminergic neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), when compared to ventral midbrain of control mice treated with vehicle alone. Thiol residues of the critical cysteines in Akt are oxidized to a greater degree in mice treated with MPTP, which is reflected as a 40% loss of reduced Akt. Association of oxidatively modified Akt with the phosphatase PP2A, which can lead to enhanced dephosphorylation of pAkt, was significantly stronger after MPTP treatment. Maintaining the protein thiol homeostasis by thiol antioxidants prevented loss of reduced Akt, decreased association with PP2A, and maintained pAkt levels. Overexpression of glutaredoxin, a protein disulfide oxidoreductase, in human primary neurons helped sustain reduced state of Akt and abolished MPP(+)-mediated pAkt loss. We demonstrate for the first time the selective loss of Akt activity, in vivo, due to oxidative modification of Akt and provide mechanistic insight into oxidative stress-induced down-regulation of cell survival pathway in mouse midbrain following exposure to MPTP.

Selective activation of p38 mitogen-activated protein kinase in dopaminergic neurons of substantia nigra leads to nuclear translocation of p53 in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated mice.

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by the degeneration of the dopaminergic neurons in the substantia nigra pars compacta (SNpc). Activation of the mixed lineage kinase and c-Jun N-terminal kinase (JNK) has been reported in models of PD. Our focus was to discern whether distinct pathways were activated in cell-specific manner within the SNpc. We now demonstrate the selective phosphorylation of p38 MAP kinase within the dopaminergic neurons, whereas JNK activation occurs predominantly in the microglia. p38 activation results in downstream phosphorylation of p53 and increased p53 mediated transcription of Bax and Puma in the ventral midbrain. Treatment with p38 inhibitor, SB239063 protected primary dopaminergic neurons derived from human progenitor cells from MPP(+) mediated cell death and prevented the downstream phosphorylation of p53 and its translocation to the nucleus in vivo, in the ventral midbrain. The increased staining of phosphorylated p38 in the surviving neurons of SNpc in human brain sections from patients with PD and in MPTP treated mice but not in the ventral tegmental area provides further evidence suggesting a role for p38 in the degeneration of dopaminergic neurons of SNpc. We thus demonstrate the cell specific activation of MAP kinase pathways within the SNpc after MPTP treatment emphasizing the role of multiple signaling cascades in the pathogenesis and progression of the disease. Selective inhibitors of p38 may therefore, help preserve the surviving neurons in PD and slow down the disease progression.

Activation of apoptosis signal regulating kinase 1 (ASK1) and translocation of death-associated protein, Daxx, in substantia nigra pars compacta in a mouse model of Parkinson's disease: protection by alpha-lipoic acid.

Parkinson's disease (PD), a neurodegenerative disorder, causes severe motor impairment due to loss of dopaminergic neurons in substantia nigra pars compacta (SNpc). MPTP, a neurotoxin that causes dopaminergic cell loss in mice, was used in an animal model to study the pathogenic mechanisms leading to neurodegeneration. We observed the activation of apoptosis signal regulating kinase (ASK1, MAPKKK) and phosphorylation of its downstream targets MKK4 and JNK, 12 h after administration of a single dose of MPTP. Further, Daxx, the death-associated protein, translocated to the cytosol selectively in SNpc neurons seemingly due to MPTP mediated down-regulation of DJ-1, the redox-sensitive protein that binds Daxx in the nucleus. Coadministration of alpha-lipoic acid (ALA), a thiol antioxidant, abolished the activation of ASK1 and phosphorylation of downstream kinases, MKK4, and JNK and prevented the down-regulation of DJ-1 and translocation of Daxx to the cytosol seen after MPTP. ALA also attenuated dopaminergic cell loss in SNpc seen after subchronic MPTP treatment. Our studies demonstrate for the first time that MPTP triggers death signaling pathway by activating ASK1 and translocating Daxx, in vivo, in dopaminergic neurons in SNpc of mice and thiol antioxidants, such as ALA terminate this cascade and afford neuroprotection.

Synthesis, molecular docking and PTP1B inhibitory activity of functionalized 4,5-dihydronaphthofurans and dibenzofurans.

Protein tyrosine phosphatase 1B (PTP1B) is an enzyme that plays a critical role in down-regulating insulin signaling through dephosphorylation of the insulin receptor. Inhibitors of PTP1B showed increased insulin sensitivity and normalize plasma glucose level and thus are useful therapeutic agents for the treatment of diabetes. A series of functionalized 4,5-dihydronaphthofurans and dibenzofurans were synthesized, studied through molecular docking and evaluated for their PTP1B inhibitory activity.

Isolated Tear Of Posterolateral Bundle Of Anterior Cruciate Ligament.

Anterior cruciate ligament injuries are very commonly encountered during routine MRI reporting and various signs have been described for their identification. However, the diagnosis of isolated bundle tears is difficult using MRI, thus can be easily overlooked, especially isolated tear of posterolateral bundle. We present a case of a young male with "Gap" and "Footprint" signs on MRI knee joint, which are considered highly specific of posterolateral ACL bundle tear.

Constitutive expression and functional characterization of mitochondrial glutaredoxin (Grx2) in mouse and human brain.

Oxidative stress and mitochondrial dysfunction caused by loss of complex I activity are presumed to be primary events leading to neurodegeneration in Parkinson's disease. Mitochondrial glutaredoxin (Grx2), a glutathione-dependent thiol disulfide oxidoreductase helps maintain redox homeostasis in the mitochondria. We therefore, examined the constitutive expression of Grx2 in brain and its role in MPTP-mediated mitochondrial dysfunction in the extrapyramidal system. Grx2 is constitutively expressed in both neuron and glia in mouse and human brain including the neurons in human substantia nigra. Grx2 mRNA and protein were transiently upregulated in midbrain and striatum 1 h but not 4 h after a single dose of MPTP. Downregulation of Grx2 using antisense oligonucleotides, in vivo, in mouse brain resulted in partial loss of complex I activity indicating that Grx2 may help maintain complex I function in the mitochondria. Further, overexpression of Grx2 abolished MPP(+)-mediated toxicity in vitro in neuroblastoma cells. Our results demonstrate the probable role of Grx2 in maintenance of the redox milieu in mitochondria and its potential neuroprotective role in preserving mitochondrial integrity in neurodegenerative diseases, such as Parkinson's disease.

Epidermoid cyst of perineum: a rare case in a young female.

Epidermoid cyst is a common, cutaneous, benign lesion that is frequently seen on the face, neck and trunk. It is rarely seen in the perineal region. The differential diagnosis of perineal cystic lesions includes a wide range of lesions, with an epidermoid cyst being a rare entity to be considered, and only a few such cases have been reported in the literature. Our case was a young Asian female who presented with painless perineal swelling for the past 6 months and was diagnosed as having an epidermoid cyst on the basis of diffusion-weighted MRI and contrast enhancement pattern, which was later confirmed by histopathological findings.

Down-regulation of glutaredoxin by estrogen receptor antagonist renders female mice susceptible to excitatory amino acid mediated complex I inhibition in CNS.

beta-N-oxalyl-amino-L-alanine, (L-BOAA), an excitatory amino acid, acts as an agonist of the AMPA subtype of glutamate receptors. It inhibits mitochondrial complex I in motor cortex and lumbosacral cord of male mice through oxidation of critical thiol groups, and glutaredoxin, a thiol disulfide oxido-reductase, helps maintain integrity of complex I. Since incidence of neurolathyrism is less common in women, we examined the mechanisms underlying the gender-related effects. Inhibition of complex I activity by L-BOAA was seen in male but not female mice. Pretreatment of female mice with estrogen receptor antagonist ICI 182,780 or tamoxifen sensitizes them to L-BOAA toxicity, indicating that the neuroprotection is mediated by estrogen receptors. L-BOAA triggers glutathione (GSH) loss in male mice but not in female mice, and only a small but significant increase in oxidized glutathione (GSSG) was seen in females. As a consequence, up-regulation of gamma-glutamyl cysteinyl synthase (the rate-limiting enzyme in glutathione synthesis) was seen only in male mouse CNS but not in females. Both glutathione reductase and glutaredoxin that reduce oxidized glutathione and protein glutathione mixed disulfides, respectively, were constitutively expressed at higher levels in females. Furthermore, glutaredoxin activity in female mice was down-regulated by estrogen antagonist indicating its regulation by estrogen receptor. The higher constitutive expression of glutathione reductase and glutaredoxin could potentially confer neuroprotection to female mice.

Large hiatal hernia in infancy with right intrathoracic stomach along with left sided morgagni hernia.

Congenital diaphragmatic hernia is a very common intrathoracic fetal anomaly with Morgagni hernia typically seen on right side anteriorly and Bochdalek hernia on left side posteriorly, because of the protective effects of liver and heart on either side respectively. Hiatal hernias range from herniation of a small portion of stomach into thoracic cavity to herniation of entire stomach into the left thoracic cavity. Very rarely the herniated stomach has been reported in the right thoracic cavity. Early diagnosis and treatment of all diaphragmatic hernias is essential to reduce the associated morbidity and mortality. We present a very rare and interesting case of an 18 months old baby girl with reverse scenarios. She had a large hiatal hernia with right intrathoracic stomach along with a left sided Morgagni hernia in combination.

DJ-1 loss by glutaredoxin but not glutathione depletion triggers Daxx translocation and cell death.

Environmental and genetic causes are implicated in the etiopathogenesis of Parkinson's disease (PD), a neurodegenerative movement disorder. DJ-1, a putative gene recessively linked to early onset PD, functions as an antioxidant, transcriptional co-activator, and molecular chaperone. We examined DJ-1 status following global perturbation of protein thiol homeostasis by depleting cellular antioxidant glutathione or downregulating glutaredoxin 1, a thiol disulfide oxidoreductase, wherein both paradigms generate oxidative stress. While these perturbations did not affect expression of DJ-1 mRNA, downregulation of glutaredoxin 1 but not glutathione depletion caused loss of DJ-1 protein, translocation of Daxx (a death-associated protein) from nucleus, and cell death. Overexpression of wild-type DJ-1, but not the cysteine mutants, prevented Daxx translocation and cytotoxicity. Protease inhibitors prevented constitutive DJ-1 loss. Residual DJ-1 was present in reduced state, indicating that DJ-1 when oxidized was degraded through proteolysis. Thus, loss of DJ-1 occurring through its oxidative modification and subsequent proteolysis mediated through dysregulation of thiol disulfide oxidoreductase may contribute to pathogenesis of sporadic PD, thus providing a link between environmental challenges and constitutive levels of this vital protein.

Redox activated MAP kinase death signaling cascade initiated by ASK1 is not activated in female mice following MPTP: novel mechanism of neuroprotection.

Incidence of Parkinson's disease (PD) is lower in women compared to men (1:1.46), which is reflected in animal models. However, precise mechanisms are unclear. Administration of MPTP (1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine) to female mice does not lead to mitochondrial complex I inhibition as seen in males and the progressive dopaminergic cell loss in substantia nigra (SNpc) is significantly attenuated. Redox driven apoptotic signaling pathways regulated by thiol disulfide oxidoreductase(s) have been implicated in the neurodegeneration seen in PD. Oxidation of thioredoxin leads to activation of apoptosis signal regulating kinase 1 (ASK1; MAPKKK) initiating cell death cascade through MAP kinase(s). Higher constitutive expression of enzymes involved in cellular redox maintenance, such as glutathione reductase, thioredoxin, and thioredoxin reductase is observed in female brain. Exposure to MPTP activates ASK1 in male but not in female mice. Higher expression of Trx in females potentially prevents ASK1 activation. Downstream of ASK1, phosphorylation of p38 MAP kinase is seen in male but not female mice. Expression of DJ-1, the redox sensing protein is higher in females and the loss of nuclear DJ-1, followed by translocation of Daxx (death associated protein) from the nucleus to the cytosol, which promotes ASK1 mediated death cascade is not seen in females. The enzymes involved in redox maintenance potentially could play a crucial role in preventing the activation of redox driven death signaling cascade and offer neuroprotection. Theraupeutic strategies that help maintain redox homeostasis may help prevent the progressive neurodegeneration seen in PD.

Knockdown of cytosolic glutaredoxin 1 leads to loss of mitochondrial membrane potential: implication in neurodegenerative diseases.

Mitochondrial dysfunction including that caused by oxidative stress has been implicated in the pathogenesis of neurodegenerative diseases. Glutaredoxin 1 (Grx1), a cytosolic thiol disulfide oxido-reductase, reduces glutathionylated proteins to protein thiols and helps maintain redox status of proteins during oxidative stress. Grx1 downregulation aggravates mitochondrial dysfunction in animal models of neurodegenerative diseases, such as Parkinson's and motor neuron disease. We examined the mechanism underlying the regulation of mitochondrial function by Grx1. Downregulation of Grx1 by shRNA results in loss of mitochondrial membrane potential (MMP), which is prevented by the thiol antioxidant, alpha-lipoic acid, or by cyclosporine A, an inhibitor of mitochondrial permeability transition. The thiol groups of voltage dependent anion channel (VDAC), an outer membrane protein in mitochondria but not adenosine nucleotide translocase (ANT), an inner membrane protein, are oxidized when Grx1 is downregulated. We then examined the effect of beta-N-oxalyl amino-L-alanine (L-BOAA), an excitatory amino acid implicated in neurolathyrism (a type of motor neuron disease), that causes mitochondrial dysfunction. Exposure of cells to L-BOAA resulted in loss of MMP, which was prevented by overexpression of Grx1. Grx1 expression is regulated by estrogen in the CNS and treatment of SH-SY5Y cells with estrogen upregulated Grx1 and protected from L-BOAA mediated MMP loss. Our studies demonstrate that Grx1, a cytosolic oxido-reductase, helps maintain mitochondrial integrity and prevents MMP loss caused by oxidative insult. Further, downregulation of Grx1 leads to mitochondrial dysfunction through oxidative modification of the outer membrane protein, VDAC, providing support for the critical role of Grx1 in maintenance of MMP.