Neurosyphilis complicated by anti-γ-aminobutyric acid-B receptor encephalitis: A case report.

BACKGROUND: Syphilis is an infectious disease caused by Treponema pallidum that can invade the central nervous system, causing encephalitis. Few cases of anti-N-methyl-D-aspartate receptor autoimmune encephalitis (AE) secondary to neurosyphilis have been reported. We report a neurosyphilis patient with anti-γ-aminobutyric acid-B receptor (GABABR) AE. CASE SUMMARY: A young man in his 30s who presented with acute epileptic status was admitted to a local hospital. He was diagnosed with neurosyphilis, according to serum and cerebrospinal fluid (CSF) tests for syphilis. After 14 d of antiepileptic treatment and anti-Treponema pallidum therapy with penicillin, epilepsy was controlled but serious cognitive impairment, behavioral, and serious psychiatric symptoms were observed. He was then transferred to our hospital. The Mini-Mental State Examination (MMSE) crude test results showed only 2 points. Cranial magnetic resonance imaging revealed significant cerebral atrophy and multiple fluid-attenuated inversion recovery high signals in the white matter surrounding both lateral ventricles, left amygdala and bilateral thalami. Anti-GABABR antibodies were discovered in CSF (1:3.2) and serum (1:100). The patient was diagnosed with neurosyphilis complicated by anti-GABABR AE, and received methylprednisolone and penicillin. Following treatment, his mental symptoms were alleviated. Cognitive impairment was significantly improved, with a MMSE of 8 points. Serum anti-GABABR antibody titer decreased to 1:32. The patient received methylprednisolone and penicillin after discharge. Three months later, the patient's condition was stable, but the serum anti-GABABR antibody titer was 1:100. CONCLUSION: This patient with neurosyphilis combined with anti-GABABR encephalitis benefited from immunotherapy.

Discovery and Development of 4-Hydroxyphenylpyruvate Dioxygenase as a Novel Crop Fungicide Target.

Plant pathogenic fungi pose a significant threat to crop yields and quality, and the emergence of fungicide resistance has further exacerbated the problem in agriculture. Therefore, there is an urgent need for efficient and environmentally friendly fungicides. In this study, we investigated the antifungal activity of (+)-Usnic acid and its inhibitory effect on crop pathogenic fungal 4-hydroxyphenylpyruvate dioxygenases (HPPDs) and determined the structure of Zymoseptoria tritici HPPD (ZtHPPD)-(+)-Usnic acid complex. Thus, the antifungal target of (+)-Usnic acid and its inhibitory basis toward HPPD were uncovered. Additionally, we discovered a potential lead fungicide possessing a novel scaffold that displayed remarkable antifungal activities. Furthermore, our molecular docking analysis revealed the unique binding mode of this compound with ZtHPPD, explaining its high inhibitory effect. We concluded that HPPD represents a promising target for the control of phytopathogenic fungi, and the new compound serves as a novel starting point for the development of fungicides and dual-purpose pesticides.

Molecular epidemiology of coxsackievirus A16 circulating in children in Beijing, China from 2010 to 2019.

BACKGROUND: Coxsackievirus A16 (CVA16) is one of the major etiological agents of hand, foot and mouth disease (HFMD). This study aimed to investigate the molecular epidemiology and evolutionary characteristics of CVA16. METHODS: Throat swabs were collected from children with HFMD and suspected HFMD during 2010-2019. Enteroviruses (EVs) were detected and typed by real-time reverse transcription-polymerase chain reaction (RT-PCR) and RT-PCR. The genotype, evolutionary rate, the most recent common ancestor, population dynamics and selection pressure of CVA16 were analyzed based on viral protein gene (VP1) by bioinformatics software. RESULTS: A total of 4709 throat swabs were screened. EVs were detected in 3180 samples and 814 were CVA16 positive. More than 81% of CVA16-positive children were under 5 years old. The prevalence of CVA16 showed obvious periodic fluctuations with a high level during 2010-2012 followed by an apparent decline during 2013-2017. However, the activities of CVA16 increased gradually during 2018-2019. All the Beijing CVA16 strains belonged to sub-genotype B1, and B1b was the dominant strain. One B1c strain was detected in Beijing for the first time in 2016. The estimated mean evolutionary rate of VP1 gene was 4.49 × 10-3 substitution/site/year. Methionine gradually fixed at site-23 of VP1 since 2012. Two sites were detected under episodic positive selection, one of which (site-223) located in neutralizing linear epitope PEP71. CONCLUSIONS: The dominant strains of CVA16 belonged to clade B1b and evolved in a fast evolutionary rate during 2010-2019 in Beijing. To provide more favorable data for HFMD prevention and control, it is necessary to keep attention on molecular epidemiological and evolutionary characteristics of CVA16.

Impact of Maternal Selenium Supplementation from Late Gestation and Lactation on Piglet Immune Function.

The present work aimed at assessing passive, innate, and acquired immunity in piglets from sows supplemented with either organic or inorganic selenium (Se). A total of 12 multiparous pregnant sows were randomly allocated to three groups: selenium-deficient, corn and soy-based diet base diet (BD), 0.3 mg Se/kg as hydroxy-selenomethionine (OH-SeMet), and 0.3 mg Se/kg as sodium selenite (SS). The feeding trial was carried out from gd 84 to weaning on postpartum day 21 (ppd 21). On gd 98 and 105, sows were vaccinated with hen egg white lysozyme (HEWL) to assess passive immunity. On ppd 23, weaned piglets were intramuscularly challenged with lipopolysaccharide (LPS) to trigger an acute-phase response. On ppd 14, 28, and 35, piglets were vaccinated with ovalbumin (OVA) to assess OVA-specific immunoglobulin G (IgG) and dermal hypersensitivity responses. Se levels in piglet plasma, muscle, and liver on ppd 21 were higher in OH-SeMet group. On ppd 2, piglet HEWL-specific IgG levels in OH-SeMet group were significantly increased. IL-10 and haptoglobin (HP) levels in OH-SeMet group were significantly increased 2 h and 48 h post-LPS simulation, respectively. The OVA-specific IgG levels in BD group were significantly higher than the other two groups, and the IL-4 concentration following whole blood ex vivo challenge with either OVA or mitogen was significantly increased in OH-SeMet group. OVA-specific skin swelling was lower in OH-SeMet and SS groups at 3 h and 6 h. This suggests that sow supplementation with OH-SeMet enhances mainly passive immunity through IgG maternal transfer and can influence piglet innate and acquired immunity.

TFP5 peptide, derived from CDK5-activating cofactor p35, provides neuroprotection in early-stage of adult ischemic stroke.

Cyclin-dependent kinase 5 (CDK5) is a multifaceted protein shown to play important roles in the central nervous system. Abundant evidence indicates that CDK5 hyperactivities associated with neuronal apoptosis and death following ischemic stroke. CDK5 activity increases when its cofactor p35 cleaves into p25 during ischemia. Theoretically, inhibition of CDK5/p25 activity or reduction of p25 would be neuroprotective. TFP5, a modified 24-aa peptide (Lys254-Ala277) derived from p35, was found to effectively inhibit CDK5 hyperactivity and improve the outcomes of Alzheimer's disease and Parkinson's disease in vivo. Here, we showed that intraperitoneal injection of TFP5 significantly decreased the size of ischemia in early-stage of adult ischemic stroke rats. Relative to controls, rats treated with TFP5 displayed reduced excitotoxicity, neuroinflammation, apoptosis, astrocytes damage, and blood-brain barrier disruption. Our findings suggested that TFP5 might serve as a potential therapeutic candidate for acute adult ischemic stroke.

Lipopolysaccharide induces acute bursal atrophy in broiler chicks by activating TLR4-MAPK-NF-κB/AP-1 signaling.

We investigated the mechanisms that induce atrophy of the chicken bursa of Fabricius (BF) upon lipopolysaccharide (LPS) treatment in young chicks. LPS treatment resulted in ∼36% decrease in bursal weight within 36 h (P < 0.01). Histological analysis showed infiltration of eosinophilic heterophils and nucleated oval shaped RBCs in or near blood vessels of the BF from LPS-treated chicks. Scanning electron micrographs showed severe erosion and breaks in the mucosal membrane at 12 h and complete exuviation of bursal mucosal epithelial cells at 36 h. We observed decreased cell proliferation (low PCNA positivity) and increased apoptosis (high TUNEL and ssDNA positivity) in the BF 12-72 h after LPS treatment. RNA-seq analysis of the BF transcriptome showed 736 differentially expressed genes with most expression changes (637/736) 12 h after LPS treatment. KEGG pathway analysis identified TLR4-MAPK-NF-κB/AP-1 as the key signaling pathway affected in response to LPS stimulation. These findings indicate LPS activates the TLR4-MAPK-NF-κB/AP-1 signaling pathway that mediates acute atrophy of the chicken bursa of Fabricius by inducing inflammation and apoptosis.

TFP5 is comparable to mild hypothermia in improving neurological outcomes in early-stage ischemic stroke of adult rats.

AIM: We compared the efficacy of a modified truncated 24-aa peptide (TFP5), derived from the cyclin-dependent kinase 5 (CDK5)-activating cofactor p35, with mild hypothermia (MH), and determined whether the efficacy of TFP5 is affected by MH. METHODS: Ischemic stroke was induced in adult male Sprague-Dawley rats for 2h. Immediately after initiating reperfusion, TFP5, MH, or the combination of the two were administrated. 48h after reperfusion, neurological outcomes were evaluated. RESULTS: Rats that received either MH, TFP5, or the combined treatment showed smaller brain infarct size than normothermia control (NT), and there was no apparent difference among these three treatment groups. The neurological deficit was significantly improved only by the combined treatment. MH or TFP5 ameliorated the blood-brain barrier (BBB) disruption in ischemic regions with similar efficacy, whereas the combination of them had a trend toward better effect. Besides, the cleavage of p35 into p25 and apoptosis in ischemic regions was inhibited by TFP5 or the combination, but not by MH alone. CONCLUSIONS: TFP5 is comparable to MH in improving neurological outcomes in early-stage adult ischemic stroke. When TFP5 is given along with MH, less neurological deficit tends to be achieved.

TFP5 prevents 1-methyl-4-phenyl pyridine ion-induced neurotoxicity in mouse cortical neurons.

The present study aimed to investigate the protective effect of a modified p5 peptide, TFP5, on 1-methyl-4-phenyl pyridine ion (MPP+)-induced neurotoxicity in cortical neurons and explore the therapeutic effect of TFP5 on Parkinson's disease (PD). MPP+ was applied to a primary culture of mouse cortical neurons to establish the cell model of PD. Neurons were divided into four groups: Control, model (MPP+), scrambled peptide (Scb) (Scb + MPP+) and TFP5 (TFP5 + MPP+) groups. Pretreatment with Scb or TFP5 was applied to the latter two groups, respectively, for 3 h, while phosphate-buffered saline was applied to the control and model groups. MPP+ was then applied to all groups, with the exception of the control group, and neurons were cultured for an additional 24 h. Neuron viability was evaluated using a Cell Counting kit-8 (CCK8) assay. To explore the mechanism underlying the protective effects of TFP5, the expression levels of p35, p25 and phosphorylated myocyte enhancer factor 2 (p-MEF2D) were determined by western blotting. Fluorescence microscopy showed that TFP5 was able to pass through cell membranes and distribute around the nucleus. CCK8 assay showed that neuronal apoptosis was dependent on MPP+ concentration and exposure time. Cell viability decreased significantly in the model group compared with the control group (55±7 vs. 100±0%; P<0.01), and increased significantly in the TFP5 group compared with the model group (98±2 vs. 55±5%; P<0.01) and Scb group (98±2 vs. 54±4%; P<0.01). Scb exhibited no protective effect. Western blotting results showed that MPP+ induced p25 and p-MEF2D expression, TFP5 and Scb did not affect MPP+-induced p25 expression, but TFP5 reduced MPP+-induced p-MEF2D expression. In summary, TFP5 protects against MPP+-induced neurotoxicity in mouse cortical neurons, possibly through inhibiting the MPP+-induced formation and elevated kinase activity of a cyclin-dependent kinase 5/p25 complex.

[Missense mutation R1345Q in CACNA1A gene causes a new type of ataxia with episodic tremor: clinical features, genetic analysis and treatment in a familial case].

OBJECTIVE: Mutations in CACNA1A, which encodes the P/Q-type calcium channel subunit, are responsible for at least 3 allelic diseases, namely type 2 episodic ataxia (EA-2), familial hemiplegic migraine?type-1 (FHM1), and spinocerebellar ataxia type-6?(SCA 6). Herein we present a case of ataxia with episodic tremors in a 19-year-old man with a missense mutation of CACNA1A gene and summarize the clinical features, genetic analysis and treatment in this case and in his affected family members. METHODS: Physical examinations were conducted for the patient and his affected family members. DNA sample from the proband was analyzed with next-generation sequencing technology to identify the causative mutation. Sanger sequencing was used to confirm the gene mutation in the family members. RESULTS: Physical examinations of the patient revealed signs of ataxia, drunken gait, and tremor of his head and body. Four other members in his family had similar but much milder symptoms. A heterozygous missense mutation in CACNA1A (NM_001127221.1 c.4034G->A, p.R1345Q, exon 25) was identified in the proband, which was confirmed in the affected family members. The proband did not respond to methazolamide treatment, but his tremor symptom was well controlled with flunarizine, a calcium channel blocker. CONCLUSION: Based on the clinical features, mutation analysis and treatment response, we suggest that this patient with a missense CACNA1A mutation, R1345Q, has a new type of ataxia with episodic tremor other than any of EA2, FHM1, or SCA 6.

Glibenclamide enhances the effects of delayed hypothermia after experimental stroke in rats.

In order to evaluate whether glibenclamide can extend the therapeutic window during which induced hypothermia can protect against stroke, we subjected adult male Sprague-Dawley rats to middle cerebral artery occlusion (MCAO). We first verified the protective effects of hypothermia induced at 0, 2, 4 or 6h after MCAO onset, and then we assessed the effects of the combination of glibenclamide and hypothermia at 6, 8 or 10h after MCAO onset. At 24h after MCAO, we assessed brain edema, infarct volume, modified neurological severity score, Evans Blue leakage and expression of Sulfonylurea receptor 1 (SUR1) protein and pro-inflammatory factors. No protective effects were observed when hypothermia was induced too long after MCAO. At 6h after MCAO onset, hypothermia alone failed to decrease cerebral edema and infarct volume, but the combination of glibenclamide and hypothermia decreased both. The combination also improved neurological outcome, ameliorated blood-brain barrier damage and decreased levels of COX-2, TNF-α and IL-1ß. These results suggest that glibenclamide enhances and extends the therapeutic effects of delayed hypothermia against ischemia stroke, potentially by ameliorating blood-brain barrier damage and declining levels of pro-inflammatory factors.

Regnase-1 in microglia negatively regulates high mobility group box 1-mediated inflammation and neuronal injury.

Extracellular high mobility group box 1 (HMGB1) has been demonstrated to function as a proinflammatory cytokine and induces neuronal injury in response to various pathological stimuli in central nervous system (CNS). However, the regulatory factor involved in HMGB1-mediated inflammatory signaling is largely unclear. Regulatory RNase 1 (Regnase-1) is a potent anti-inflammation enzyme that can degrade a set of mRNAs encoding proinflammatory cytokines. The present study aims to determine the role of Regnase-1 in the regulation of HMGB1-mediated inflammatory injury in CNS. Cultured microglia and rat brain were treated with recombinant HMGB1 to examine the induction of Regnase-1 expression. Moreover, the role of Regnase-1 in modulating the expression of inflammatory cytokines and neuronal injury was then investigated in microglia by specific siRNA knockdown upon HMGB1 treatment. Results showed that HMGB1 could significantly induce the de novo synthesis of Regnase-1 in cultured microglia. Consistently, Regnase-1 was elevated and found to be co-localized with microglia marker in the brain of rat treated with HMGB1. Silencing Regnase-1 in microglia enhanced HMGB1-induced expression of proinflammatory cytokines and exacerbated neuronal toxicity. Collectively, these results suggest that Regnase-1 can be induced by HMGB1 in microglia and negatively regulates HMGB1-mediated neuroinflammation and neuronal toxicity.

Hypothermia followed by rapid rewarming exacerbates ischemia-induced brain injury and augments inflammatory response in rats.

Hypothermia followed by slow rewarming is neuroprotective for ischemic stroke. However, slow rewarming causes patients' longer stay in intensive care unit and increases the risk of hypothermic complications. Hypothermia followed by rapid rewarming (HTRR) is more convenient; but it exacerbates intracranial hypertension for patients with massive hemispheric infarcts. The present study aims to investigate in detail how HTRR exacerbates ischemic brain injury and what are underlying mechanisms. Rats subjected to transient focal ischemia by middle cerebral artery occlusion were treated with normothermia or hypothermia followed by rapid rewarming. Neurological outcome, neuronal injury, blood-brain barrier integrity and expressions of inflammatory cytokines were observed. Results showed that HTRR at a rate of 3 °C/20 min increased both neurological deficit score and Longa score, enhanced the loss of neurons and the plasma level of neuron-specific enolase. Rapid rewarmed rats also displayed increased Evans blue dye extravasation, matrix metalloproteinase 9 level and tight junction impairment. Meanwhile, interleukin-1ß, -6, tumor necrosis factor α and cyclooxygenase-2 were markedly elevated in rapid rewarmed rats. Anti-inflammatory agent minocycline suppressed HTRR-induced elevation of inflammatory cytokines and improved neurological outcome. These results indicated that HTRR significantly impaired neurovascular unit and augmented proinflammatory response in stroke.

Preconditioning with recombinant high-mobility group box 1 induces ischemic tolerance in a rat model of focal cerebral ischemia-reperfusion.

Preconditioning with ligands of toll-like receptors (TLRs) is a powerful neuroprotective approach whereby a low dose of stimulus confers significant protection against subsequent substantial brain damage by reprogramming the ischemia-activated TLRs signaling. Herein, we aim to explore whether preconditioning with recombinant high-mobility group box 1 (rHMGB1), one of the TLRs ligands, decreases cerebral ischemia-reperfusion injury (IRI). Rats were intracerebroventricularly pretreated with rHMGB1, 1 or 3 days before induction of middle cerebral artery occlusion. Results showed that preconditioning with rHMGB1 1 day, but not 3 days, prior to ischemia dramatically reduced neurological deficits, infarct size, brain swelling, cell apoptosis, and blood-brain barrier permeability. Interleukin-1R-associated kinase-M (IRAK-M), a critical negative regulator of TLRs signaling, was robustly increased in response to brain IRI and was further elevated by rHMGB1 pretreatment, indicating its role associated with the rHMGB1 preconditioning-mediated ischemic tolerance. In vitro and in vivo assays indicated that the induced IRAK-M expression was localized in microglia. In addition, TLR4 specific inhibitor TAK-242 abolished the neuroprotective effects and the induction of IRAK-M offered by rHMGB1 preconditioning. Collectively, our study demonstrates that rHMGB1 preconditioning is neuroprotective during cerebral IRI, which is associated with activated TLR4/IRAK-M signaling in microglia. We found that high-mobility group box 1 (HMGB1) pretreatment conditioned the brain against subsequent ischemia-reperfusion injury. We propose the following mechanism for HMGB1 preconditioning-mediated ischemic tolerance: through toll-like receptor TLR4, HMGB1 preconditioning magnifies the up-regulation of interleukin-1R-associated kinase-M (IRAK-M) induced by ischemia-reperfusion in microglia, resulting in the decreased phosphorylation of IRAK-1. These findings are helpful in understanding the endogenous mechanisms that counteract ischemic insults.

Prolonged hypothermia exposure diminishes neuroprotection for severe ischemic-hypoxic primary neurons.

This study aimed to identify optimal mild hypothermic (MH) condition that would provide the best protection for neuronal cells undergoing severe ischemia and hypoxia. We also sought to determine if longer exposure to mild hypothermia would confer greater protection to severe ischemia and hypoxia in these cells. We designed a primary neuronal cell model for severe glucose and oxygen deprivation/reoxygenation (OGD/R) to simulate the hypoxic-ischemic condition of patients with severe stroke, trauma, or hypoxic-ischemic encephalopathy. We evaluated the viability of these neurons following 3 h of OGD/R and variable MH conditions including different temperatures and durations of OGD/R exposure. We further explored the effects of the optimal MH condition on several parts which are associated with mitochondrial apoptosis pathway: intracellular calcium, reactive oxygen species (ROS), and mitochondrial transmembrane potential (MTP). The results of this study showed that the apoptosis proportion (AP) and cell viability proportion (CVP) after OGD/R significantly varied depending on which MH condition cells were exposed to (p < 0.001). Further, our findings showed that prolonged MH reduced the neuroprotection to AP and CVP. We also determined that the optimal MH conditions (34 °C for 4.5 h) reduced intracellular calcium, ROS, and recovered MTP. These findings indicate that there is an optimal MH treatment strategy for severely hypoxia-ischemic neurons, prolonged duration might diminish the neuroprotection, and that MH treatment likely initiates neuroprotection by inhibiting the mitochondrial apoptosis pathway.

Combination of mild hypothermia with neuroprotectants has greater neuroprotective effects during oxygen-glucose deprivation and reoxygenation-mediated neuronal injury.

Co-treatment of neuroprotective reagents may improve the therapeutic efficacy of hypothermia in protecting neurons during ischemic stroke. This study aimed to find promising drugs that enhance the neuroprotective effect of mild hypothermia (MH). 26 candidate drugs were selected based on different targets. Primary cultured cortical neurons were exposed to oxygen-glucose deprivation and reoxygenation (OGD/R) to induce neuronal damage, followed by either single treatment (a drug or MH) or a combination of a drug and MH. Results showed that, compared with single treatment, combination of MH with brain derived neurotrophic factor, glibenclamide, dizocilpine, human urinary kallidinogenase or neuroglobin displayed higher proportion of neuronal cell viability. The latter three drugs also caused less apoptosis rate in combined treatment. Furthermore, co-treatment of those three drugs and MH decreased the level of reactive oxygen species (ROS) and intracellular calcium accumulation, as well as stabilized mitochondrial membrane potential (MMP), indicating the combined neuroprotective effects are probably via inhibiting mitochondrial apoptosis pathway. Taken together, the study suggests that combined treatment with hypothermia and certain neuroprotective reagents provide a better protection against OGD/R-induced neuronal injury.

Intermittent hypothermia is neuroprotective in an in vitro model of ischemic stroke.

OBJECTIVE: To investigate whether the intermittent hypothermia (IH) protects neurons against ischemic insult and the potential molecular targets using an in vitro ischemic model of oxygen glucose deprivation (OGD). METHODS: Fetal rat cortical neurons isolated from Day E18 rat embryos were subjected to 90-min OGD and hypothermia treatments during reoxygenation before examining the changes in microscopic morphology, cell viability, microtubule- associated protein 2 (MAP-2) release, intracellular pH value and calcium, reactive oxygen species (ROS) generation, mitochondrial membrane potential (△Ψm) and neuronal death using cell counting kit (CCK-8), enzyme-linked immunosorbent assay (ELISA), BCECF AM, Fluo-3 AM, DCFH-DA and dihydroethidium (DHE), JC-1 staining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), respectively. RESULTS: 90-min OGD induced morphologic abnormalities, cell viability decline, MAP-2 release, intracellular acidosis, calcium overload, increased ROS generation, △Ψm decrease and cell death in primary neurons, which was partially inhibited by continuous hypothermia (CH) and intermittent hypothermia (IH). Interestingly, 6-h CH was insufficient to reduce intracellular calcium overload and stabilize mitochondrial membrane potential (△Ψm), while 12-h CH was effective in reversing the above changes. All IH treatments (6×1 h, 4×1.5 h or 3×2 h) effectively attenuated intracellular free calcium overload, inhibited ROS production, stabilized mitochondrial membrane potential (△Ψm) and reduced delayed cell death in OGD-treated cells. However, only IH intervals longer than 1.5 h appeared to be effective in preventing cell viability loss and intracellular pH decline. CONCLUSION: Both CH and IH were neuroprotective in an in vitro model of ischemic stroke, and in spite of shorter hypothermia duration, IH could provide a comparable neuroprotection to CH.

Cdk5 inhibitory peptide (CIP) inhibits Cdk5/p25 activity induced by high glucose in pancreatic beta cells and recovers insulin secretion from p25 damage.

Cdk5/p25 hyperactivity has been demonstrated to lead to neuron apoptosis and degenerations. Chronic exposure to high glucose (HG) results in hyperactivity of Cdk5 and reduced insulin secretion. Here, we set out to determine whether abnormal upregulation of Cdk5/p25 activity may be induced in a pancreatic beta cell line, Min6 cells. We first confirmed that p25 were induced in overexpressed p35 cells treated with HG and increased time course dependence. Next, we showed that no p25 was detected under short time HG stimulation (4-12 hrs), however was detectable in the long exposure in HG cells (24 hrs and 48 hrs). Cdk5 activity in the above cells was much higher than low glucose treated cells and resulted in more than 50% inhibition of insulin secretion. We confirmed these results by overexpression of p25 in Min6 cells. As in cortical neurons, CIP, a small peptide, inhibited Cdk5/p25 activity and restored insulin secretion. The same results were detected in co-infection of dominant negative Cdk5 (DNCdk5) with p25. CIP also reduced beta cells apoptosis induced by Cdk5/p25. These studies indicate that Cdk5/p25 hyperactivation deregulates insulin secretion and induces cell death in pancreatic beta cells and suggests that CIP may serve as a therapeutic agent for type 2 diabetes.

Overexpression of p35 in Min6 pancreatic beta cells induces a stressed neuron-like apoptosis.

Cdk5 activity has been implicated in brain development and the regulation of many neuronal processes. Recently, the expression of p35 and Cdk5 activity has been reported in pancreatic beta cells. Decreased Cdk5 activity enhanced glucose-stimulated insulin secretion. This suggests that Cdk5 may play an important role in the regulation of insulin secretion. To further understand how Cdk5 regulates insulin secretion in glucose-stimulated pancreatic ß cells, we first confirmed the presence of a low level of p35 in pancreatic Min6 cells. Next, in a time-course experiment in high glucose (25 mM) we showed that endogenous p35 increased gradually accompanied by a 3-fold increase in Cdk5 activity by 16 h. Insulin secretion, however, doubled after 2 h followed by progressive downregulation, negatively correlated with Cdk5 activity. On the other hand, overexpression of p35 in these cells resulted in more than a three-fold increase in Cdk5 activity within 2 h coupled to a 50% reduction in insulin secretion in both high and low (3 mM) glucose. Most significantly, cells overexpressing p35, treated with high glucose for 4 h, showed induction of p25, the p35-derived truncated fragment which hyperactivates Cdk5 in neurons. As a result, insulin secretion was inhibited and cells became apoptotic. Roscovitine or co-infection of dominant negative Cdk5 (dnCdk5) with p35 increased insulin secretion and inhibited apoptosis. These results suggest that the model for deregulation and hyperactivation of Cdk5 in neurodegeneration may apply to the pathology seen in type 2 diabetes (T2DM). It is consistent with the view that Alzheimer's disease and T2DM are linked metabolically and pathologically by Cdk5 in a number of ways.