Adult-onset deletion of Pten increases islet mass and beta cell proliferation in mice

Aims/hypothesis

Adult beta cells have a diminished ability to proliferate. Phosphatase and tensin homologue (PTEN) is a lipid phosphatase that antagonises the function of the mitogenic phosphatidylinositol 3-kinase (PI3K) pathway. The objective of this study was to understand the role of PTEN and PI3K signalling in the maintenance of beta cells postnatally.

Methods

We developed a Pten ^lox/lox; Rosa26 ^lacZ; RIP-CreER ⁺ model that permitted us to induce Pten deletion by treatment with tamoxifen in mature animals. We evaluated islet mass and function as well as beta cell proliferation in 3- and 12-month-old mice treated with tamoxifen (Pten deleted) vs mice treated with vehicle (Pten control).

Results

Deletion of Pten in juvenile (3-month-old) beta cells significantly induced their proliferation and increased islet mass. The expansion of islet mass occurred concomitantly with the enhanced ability of the Pten-deleted mice to maintain euglycaemia in response to streptozotocin treatment. In older mice (>12 months of age), deletion of Pten similarly increased islet mass and beta cell proliferation. This novel finding suggests that PTEN-regulated mechanisms may override the age-onset diminished ability of beta cells to respond to mitogenic stimulation. We also found that proteins regulating G1/S cell-cycle transition, such as cyclin D1, cyclin D2, p27 and p16, were altered when PTEN was lost, suggesting that they may play a role in PTEN/PI3K-regulated beta cell proliferation in adult tissue.

Conclusions/interpretation

The signals regulated by the PTEN/PI3K pathway are important for postnatal maintenance of beta cells and regulation of their proliferation in adult tissues.     

Chemical induction of hepatic apoptosis in rodents

The urge of identifying new pharmacological interventions to prevent or attenuate liver injury is of critical importance and needs an expanded experimental toolbox. Hepatocyte injury and cellular death is a prominent feature behind the pathology of liver diseases. Several research activities focused on identifying chemicals and hepatotoxicants that induce cell death by apoptosis, in addition to presenting its corresponding signaling pathway. Although such efforts provided further understanding of the mechanisms of cell death, it has also raised confusion concerning identifying the involvement of several modes of cell death including apoptosis, necrosis and fibrosis. The current review highlights the ability of several chemicals and potential hepatotoxicants to induce liver damage in rodents by means of apoptosis while the probable involvement of other modes of cell death is also exposed. Thus, several chemical substances including hepatotoxins, mycotoxins, hyperglycemia inducers, metallic nanoparticles and immunosuppressant drugs are reviewed to explore the hepatic cytotoxic spectrum they could exert on hepatocytes of rodents. In addition, the current review address the mechanism by which hepatotoxicity is initiated in hepatocytes in different rodents aiding the researcher in choosing the right animal model for a better research outcome.     

Migration Inhibitory Factor Enhances Inflammation via CD74 in Cartilage End Plates with Modic Type 1 Changes on MRI

Background

Type 1 Modic changes are characterized by edema, vascularization, and inflammation, which lead to intervertebral disc degeneration. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine closely related to the inflammatory cytokines detected in degenerative intervertebral disc tissues. However, the existence and role of MIF and its receptor CD74 in intervertebral disc degeneration have not been elucidated.

Questions/purposes

We asked whether (1) MIF and its receptor CD74 are expressed in cartilage end plates with Type 1 Modic changes, (2) MIF is associated with cartilage end plate degeneration, (3) the MIF antagonist (S, R)-3(4-hydroxyphenyl)-4, 5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1) suppresses MIF-induced inflammatory cytokine release, and (4) inflammatory cytokines are released by cartilage end plate chondrocytes via CD74 by activating the CD74 antibody (CD74Ab).

Methods

We examined MIF and CD74 expression by human cartilage end plate chondrocytes and tissues with Type 1 Modic changes from eight patients using immunocytofluorescence and immunohistochemistry. MIF production by the chondrocytes was assessed by ELISA and PCR. We compared cytokine release by chondrocytes treated with MIF in the presence or absence of exogenous ISO-1 by ELISA. Cytokine release by chondrocytes after treatment with CD74Ab was determined by ELISA.

Results

MIF was expressed in degenerated human cartilage end plate tissues and chondrocytes. Lipopolysaccharide and tumor necrosis factor α (TNF-α) upregulated MIF expression and increased MIF secretion in chondrocytes in a dose-dependent manner. MIF increased the secretion of IL-6, IL-8, and prostaglandin E2 (PGE2) in a dose-dependent manner. ISO-1 reduced the secretion of IL-6, IL-8, and PGE2. CD74Ab activated CD74 and induced release of inflammatory cytokines.

Conclusions

Chondrocytes in cartilage end plate with Type 1 Modic changes express MIF and its receptor CD74. MIF might promote the inflammatory response through CD74. MIF-induced cytokine release appears to be suppressed by ISO-1, and CD74Ab could induce cytokine release.

Clinical Relevance

The MIF/CD74 pathway may represent a crucial target for treating disc degeneration since inhibiting the function of MIF with its antagonist ISO-1 can reduce MIF-induced inflammation and exert potent therapeutic effects.     

Preparation and characterization of letrozole-loaded poly(d,l-lactide) nanoparticles for drug delivery in breast cancer therapy

Letrozole (LTZ), an aromatase inhibitor used for the treatment of hormonally-positive breast cancer in postmenopausal women, has poor water solubility, rapid metabolism, and a range of side effects. In this study, polymer-based nanoparticles (NPs) incorporating the drug have been designed and characterized, aimed to control the release, potentially maximize the therapeutic efficiency, and minimize the side effects of the drug. LTZ was incorporated into poly(d,l-lactide) (PDLLA) NPs by employing the emulsion-solvent evaporation technique using a range of drug concentrations. Loaded drug and drug-polymer interactions were studied using X-ray diffraction and NPs morphology was evaluated using scanning electron microscopy (SEM). Particle size distribution (PSD) and zeta potential of the NPs were analyzed using dynamic light scattering (DLS) and laser Doppler velocimetry (LDV), respectively. Drug content and release profile studies were carried out and determined using ultra performance liquid chromatography (UPLC). The yield of LTZ-PDLLA NPs reached as high as 85%. The NPs were spherical and smooth, regardless of LTZ concentration in the formulation. However, particle size increased from 241.6?±?1.2 to 348.7?±?6.1?nm upon increasing LTZ concentration from 0 to 30% w/w, with entrapment efficiencies reaching up to 96.8%. Drug release from the polymeric matrix was best described by Higuchi model with a predominant diffusion-based mechanism. More than 15, 46, and 86% of LTZ was released in a controlled fashion over 30?d from the 10, 20, and 30% LTZ-PDLLA NPs, respectively. Overall, LTZ-PDLLA NPs were designed with appropriate size and surface charge, high drug loading, superior entrapment efficiency, and prolonged release profile.     

Protein Energy Wasting in a Cohort of Maintenance Hemodialysis Patients in Dhaka,Bangladesh

Malnutrition is associated with high rates of mortality among patients with end stage kidney disease (ESKD). There is a paucity of data from Bangladesh, where around 35,000–40,000 people reach ESKD annually. We assessed protein-energy wasting (PEW) amongst 133 patients at a single hemodialysis setting in Dhaka. Patients were 49% male, age 50 ± 13 years, 62% were on twice-weekly hemodialysis. Anthropometric, biochemical, and laboratory evaluations revealed: BMI 24.1 ± 5.2 kg/m², mid-arm muscle circumference (MAMC) 21.6 ± 3.6 cm, and serum albumin 3.7 ± 0.6 g/dL. Based on published criteria, 18% patients had PEW and for these patients, BMI (19.8 ± 2.4 vs. 25.2 ± 5.2 kg/m²), MAMC (19.4 ± 2.4 vs. 22.2 ± 3.8 cm), serum albumin (3.5 ± 0.7 vs. 3.8 ± 0.5 g/dL), and total cholesterol (135 ± 34 vs. 159 ± 40 mg/dL), were significantly lower as compared to non-PEW patients, while hand grip strength was similar (19.5 ± 7.6 vs. 19.7 ± 7.3 kg). Inflammatory C-reactive protein levels tended to be higher in the PEW group (20.0 ± 34.8 vs. 10.0 ± 13.9 p = 0.065). Lipoprotein analyses revealed PEW patients had significantly lower low density lipoprotein cholesterol (71 ± 29 vs. 88 ± 31 mg/dL, p < 0.05) and plasma triglyceride (132 ± 51 vs. 189 ± 103 mg/dL, p < 0.05), while high density lipoprotein cholesterol was similar. Nutritional assessments using a single 24 h recall were possible from 115 of the patients, but only 66 of these were acceptable reporters. Amongst these, while no major differences were noted between PEW and non-PEW patients, the majority of patients did not meet dietary recommendations for energy, protein, fiber, and several micronutrients (in some cases intakes were 60–90% below recommendations). Malnutrition Inflammation Scores were significantly higher in PEW patients (7.6 ± 3.1 vs. 5.3 ± 2.7 p < 0.004). No discernible differences were apparent in measured parameters between patients on twice- vs. thrice-weekly dialysis. Data from a larger cohort are needed prior to establishing patient-management guidelines for PEW in this population.     

急性心肌梗塞后左室重构的超声心动图分析

用二维超声心动图对50例急性心肌梗塞患者的左室重构分析可见;前壁梗塞时;室间隔变薄、动度减弱,下后壁梗塞时,左室后壁变薄,动度减弱.心梗后左室扩大,室壁膨出,EDV、ESV显著增大(P相似文献   

Tridimensional Computer-Assisted Anatomic Dissection of Posterolateral Prostatic Neurovascular Bundles

Background

Detailed knowledge of nerve distribution in the neurovascular bundle (NVB) is essential to preserve sexual function after prostatic surgery.

Objective

To identify the location as well as the type (adrenergic, cholinergic, and sensory) of nerve fibres within the NVB and to provide a three-dimensional (3D) representation of their structural relationship in the human male foetus.

Design, setting, and participants

Serial transverse sections were performed every 150–200 μm in the pelvic portion of six human male foetuses (15–20 wk of gestation). Sections were treated with histologic and immunohistochemical methods (hematin-eosin-safran, Luxol Fast Blue, immunolabelling of protein S100, vesicular acetylcholine transporter, tyrosine hydroxylase, calcitonin gene-related peptide, and substance P). The 3D pelvic reconstruction was obtained from digitised serial sections using WinSurf software.

Measurements

NVB nerve location and type were evaluated qualitatively.

Results and limitations

The 3D reconstruction allowed precise identification of pelvic organ innervation. Nerve fibres derived from the inferior hypogastric plexus followed two courses: posterior and lateral, providing cholinergic, adrenergic, and sensory innervation to seminal vesicles, vas deferens, prostate, and urethral sphincter. Cavernous nerve fibres did not strictly follow the NVB course; they were distributed at several levels, in a fanlike formation. The main limitations of this study were the limited number of specimens available due to legal restriction and the time-consuming nature of the manually performed stages in the method.

Conclusions

The distribution of nerve fibres within the posterolateral prostatic NVB and the existence of mixed innervation in the posterior and lateral fibre courses at the level of the prostate and seminal vesicles give us an insight into how to minimise effects on sexual function during prostatic surgery. The 3D computer-assisted anatomic dissection represents an original method of applying anatomic knowledge to surgical technique to improve nerve preservation and decrease postoperative sexual complications.     

CNI-1493 inhibits Abeta production, plaque formation, and cognitive deterioration in an animal model of Alzheimer's disease

Alzheimer's disease (AD) is characterized by neuronal atrophy caused by soluble amyloid beta protein (Abeta) peptide "oligomers" and a microglial-mediated inflammatory response elicited by extensive amyloid deposition in the brain. We show that CNI-1493, a tetravalent guanylhydrazone with established antiinflammatory properties, interferes with Abeta assembly and protects neuronal cells from the toxic effect of soluble Abeta oligomers. Administration of CNI-1493 to TgCRND8 mice overexpressing human amyloid precursor protein (APP) for a treatment period of 8 wk significantly reduced Abeta deposition. CNI-1493 treatment resulted in 70% reduction of amyloid plaque area in the cortex and 87% reduction in the hippocampus of these animals. Administration of CNI-1493 significantly improved memory performance in a cognition task compared with vehicle-treated mice. In vitro analysis of CNI-1493 on APP processing in an APP-overexpressing cell line revealed a significant dose-dependent decrease of total Abeta accumulation. This study indicates that the antiinflammatory agent CNI-1493 can ameliorate the pathophysiology and cognitive defects in a murine model of AD.