Phosphorylation of the MNK1 substrate eIF4E is not required for response to acute pancreatitis.

BACKGROUND: The MNK1 protein kinase is directly activated by the MAPK pathway and is specifically expressed in pancreatic acinar cells. Both the MNK1 kinase and the MAPK pathway are required for response to pancreatitis, suggesting that their pharmacological targeting would be of therapeutic interest. Because the mRNA cap-binding protein and translation initiation factor eIF4E is the major known MNK1 substrate, one could anticipate that the protective function of MNK1 in pancreatitis is mediated by eIF4E phosphorylation. METHODS: Acute pancreatitis was induced by the intraperitoneal administration of cerulein in wild-type mice and in transgenic mice carrying two non-phosphorylatable Eif4e alleles. The expression and phosphorylation of proteins of the MNK1-eIF4E pathway was visualized by western-blotting. The severity of pancreatitis was monitored by the measure of serum amylase levels and by histopathology and immunohistochemistry using apoptosis and immune infiltrate markers. RESULTS: Despite a strong induction in MNK1 kinase activity in both wild-type and transgenic mice, precluding eIF4E phosphorylation has no impact on the severity of acute pancreatitis. Serum amylase is equally induced in both mouse genotypes and neither acinar cell apoptosis nor immune infiltrate is exacerbated. CONCLUSION: eIF4E phosphorylation is not required for response to pancreatitis indicating that the acinar-cell-specific MNK1 kinase acts in acute pancreatitis via another substrate.

FAK activity in cancer-associated fibroblasts is a prognostic marker and a druggable key metastatic player in pancreatic cancer.

Cancer-associated fibroblasts (CAFs) are considered the most abundant type of stromal cells in pancreatic ductal adenocarcinoma (PDAC), playing a critical role in tumour progression and chemoresistance; however, a druggable target on CAFs has not yet been identified. Here we report that focal adhesion kinase (FAK) activity (evaluated based on 397 tyrosine phosphorylation level) in CAFs is highly increased compared to its activity in fibroblasts from healthy pancreas. Fibroblastic FAK activity is an independent prognostic marker for disease-free and overall survival of PDAC patients (cohort of 120 PDAC samples). Genetic inactivation of FAK within fibroblasts (FAK kinase-dead, KD) reduces fibrosis and immunosuppressive cell number within primary tumours and dramatically decreases tumour spread. FAK pharmacologic or genetic inactivation reduces fibroblast migration/invasion, decreases extracellular matrix (ECM) expression and deposition by CAFs, modifies ECM track generation and negatively impacts M2 macrophage polarization and migration. Thus, FAK activity within CAFs appears as an independent PDAC prognostic marker and a druggable driver of tumour cell invasion.

eIF4A inhibition circumvents uncontrolled DNA replication mediated by 4E-BP1 loss in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) relies on hyperactivated protein synthesis. Consistently, human and mouse PDAC lose expression of the translational repressor and mTOR target 4E-BP1. Using genome-wide polysome profiling, we here explore mRNAs whose translational efficiencies depend on the mTOR/4E-BP1 axis in pancreatic cancer cells. We identified a functional enrichment for mRNAs encoding DNA replication and repair proteins, including RRM2 and CDC6. Consequently, 4E-BP1 depletion favors DNA repair and renders DNA replication insensitive to mTOR inhibitors, in correlation with a sustained protein expression of CDC6 and RRM2, which is inversely correlated with 4E-BP1 expression in PDAC patient samples. DNA damage and pancreatic lesions induced by an experimental pancreatitis model uncover that 4E-BP1/2-deleted mice display an increased acinar cell proliferation and a better recovery than WT animals. Targeting translation, independently of 4E-BP1 status, using eIF4A RNA helicase inhibitors (silvestrol derivatives) selectively modulates translation and limits CDC6 expression and DNA replication, leading to reduced PDAC tumor growth. In summary, 4E-BP1 expression loss during PDAC development induces selective changes in translation of mRNA encoding DNA replication and repair protein. Importantly, targeting protein synthesis by eIF4A inhibitors circumvents PDAC resistance to mTOR inhibition.

Neuroprotection in non-transgenic and transgenic mouse models of Alzheimer's disease by positive modulation of σ1 receptors.

The sigma-1 (σ1) receptor is an endoplasmic reticulum (ER) chaperone protein, enriched in mitochondria-associated membranes. Its activation triggers physiological responses to ER stress and modulate Ca2+ mobilization in mitochondria. Small σ1 agonist molecules activate the protein and act behaviorally as antidepressant, anti-amnesic and neuroprotective agents. Recently, several chemically unrelated molecules were shown to be σ1 receptor positive modulators (PMs), with some of them a clear demonstration of their allostericity. We here examined whether a σ1 PM also shows neuroprotective potentials in pharmacological and genetic models of Alzheimer's disease (AD). For this aim, we describe (±)-2-(3-chlorophenyl)-3,3,5,5-tetramethyl-2-oxo-[1,4,2]-oxazaphosphinane (OZP002) as a novel σ1 PM. OZP002 does not bind σ1 sites but induces σ1 effects in vivo and boosts σ1 agonist activity. OZP002 was antidepressant in the forced swim test and its effect was blocked by the σ1 antagonist NE-100 or in σ1 receptor knockout mice. It potentiated the antidepressant effect of the σ1 agonist igmesine. In mice tested for Y-maze alternation or passive avoidance, OZP002 prevented scopolamine-induced learning deficits, in a NE-100 sensitive manner. Pre-administered IP before an ICV injection of amyloid Aß25-35 peptide, a pharmacological model of Alzheimer's disease, OZP002 prevented the learning deficits induced by the peptide after one week in the Y-maze, passive avoidance and novel object tests. Biochemical analyses of the mouse hippocampi showed that OZP002 significantly decreased Aß25-35-induced increases in reactive oxygen species, lipid peroxidation, and increases in Bax, TNFα and IL-6 levels. Immunohistochemically, OZP002 prevented Aß25-35-induced reactive astrogliosis and microgliosis in the hippocampus. It also alleviated Aß25-35-induced decreases in synaptophysin level and choline acetyltransferase activity. Moreover, chronically administered in APPswe mice during 2 months, OZP002 prevented learning deficits (in all tests plus place learning in the water-maze) and increased biochemical markers. This study shows that σ1 PM with high neuropotective potential can be identified, combining pharmacological efficacy, selectivity and therapeutic safety, and identifies a novel promising compound, OZP002.

Amyloid toxicity is enhanced after pharmacological or genetic invalidation of the σ1 receptor.

The sigma-1 receptor (S1R) is a molecular chaperone which activity modulates several intracellular signals including calcium mobilization at mitochondria-associated endoplasmic reticulum membranes. S1R agonists are potent neuroprotectants against neurodegenerative insults and particularly in rodent models of Alzheimer's disease (AD). We here analyzed whether S1R inactivation modifies vulnerability to amyloid toxicity in AD models. Two strategies were used: (1) amyloid ß[25-35] (Aß25-35) peptide (1, 3, 9nmol) was injected intracerebroventricularly in mice treated repeatedly with the S1R antagonist NE-100 or in S1RKO mice, and (2) WT, APPSweInd, S1RKO, and APPSweInd/S1RKO mice were created and female littermates analyzed at 8 months of age. Learning deficits, oxidative stress, Bax level and BDNF content in the hippocampus were analyzed. Aß25-35 induced learning impairment, oxidative stress, Bax induction and BDNF alteration at lower dose in NE-100-treated mice or S1RKO mice as compared to WT animals. The extent of learning deficits and biochemical alterations were also higher in APPSweInd/S1RKO mice as compared to WT, APPSweInd, and S1RKO animals. S1R inactivation or altered S1R expression augmented the pathological status in pharmacologic and genetic AD mouse models. These observations, in relation with the well-known protective effects of S1R agonists, are coherent with a role of signal amplifier in neurodegeneration and neuroprotection proposed for S1R in AD and related neurodegenerative disorders.

An Intranasal Formulation of Erythropoietin (Neuro-EPO) Prevents Memory Deficits and Amyloid Toxicity in the APPSwe Transgenic Mouse Model of Alzheimer's Disease.

Erythropoietin (EPO) is a cytokine known to have effective cytoprotective action in the brain, particularly in ischemic, traumatic, inflammatory, and neurodegenerative conditions. We previously reported the neuroprotective effect of a low sialic form of EPO, Neuro-EPO, applied intranasally in rodent models of stroke or cerebellar ataxia and in a non-transgenic mouse model of Alzheimer's disease (AD). Here we analyzed the protective effect of Neuro-EPO in APPSwe mice, a reference transgenic mouse model of AD. Mice were administered 3 times a day, 3 days in the week with Neuro-EPO (125, 250 µg/kg) intranasally, between 12 and 14 months of age. Motor responses, general activity, and memory responses were analyzed during and after treatment. The deficits in spontaneous alternation, place learning in the water-maze, and novel object recognition observed in APPSwe mice were alleviated by the low dose of Neuro-EPO. Oxidative stress, neuroinflammation, trophic factor levels, and a synaptic marker were analyzed in the hippocampus or cortex of the animals. The increases in lipid peroxidation or in GFAP and Iba-1 contents in APPSwe mice were significantly reduced after Neuro-EPO. Activation of intrinsic and extrinsic apoptotic pathways was analyzed. The increases in Bax/Bcl-2 ratio, TNFα, or Fas ligand levels observed in APPSwe mice were reduced by Neuro-EPO. Finally, immunohistochemical and ELISA analyses of Aß1-42 levels in the APPSwe mouse cortex and hippocampus showed a marked reduction in Aß deposits and in soluble and insoluble Aß1-42 forms. This study therefore confirmed the neuroprotective activity of EPO, particularly for an intranasally deliverable formulation, devoid of erythropoietic side effects, in a transgenic mouse model of AD. Neuro-EPO alleviated memory alterations, oxidative stress, neuroinflammation, apoptosis induction, and amyloid load in 14-month-old APPSwe mice.

Learning performances and vulnerability to amyloid toxicity in the butyrylcholinesterase knockout mouse.

Butyrylcholinesterase (BChE) is an important enzyme for detoxication and metabolism of ester compounds. It also hydrolyzes the neurotransmitter acetylcholine (ACh) in pathological conditions and may play a role in Alzheimer's disease (AD). We here compared the learning ability and vulnerability to Aß toxicity in male and female BChE knockout (KO) mice and their 129Sv wild-type (Wt) controls. Animals tested for place learning in the water-maze showed increased acquisition slopes and presence in the training quadrant during the probe test. An increased passive avoidance response was also observed for males. BChE KO mice therefore showed enhanced learning ability in spatial and non-spatial memory tests. Intracerebroventricular (ICV) injection of increasing doses of amyloid-ß[25-35] (Aß25-35) peptide oligomers resulted, in Wt mice, in learning and memory deficits, oxidative stress and decrease in ACh hippocampal content. In BChE KO mice, the Aß25-35-induced deficit in place learning was attenuated in males and blocked in females. No change in lipid peroxidation or ACh levels was observed after Aß25-35 treatment in male or female BChE KO mice. These data showed that the genetic invalidation of BChE in mice augmented learning capacities and lowered the vulnerability to Aß toxicity.