Pseudomonas fluorescens alters epithelial permeability and translocates across Caco-2/TC7 intestinal cells

Background

Pseudomonas fluorescens has long been considered as a psychrotrophic microorganism. Recently, we have shown that clinical strains of P. fluorescens (biovar 1) are able to adapt at a growth temperature of 37°C or above and induce a specific inflammatory response. Interestingly, a highly specific antigen of P. fluorescens, I2, is detected in the serum of patients with Crohn's disease but the possible role of this bacterium in the disease has not yet been explored. In the present study, we examined the ability of a psychrotrophic and a clinical strain of P. fluorescens to modulate the permeability of a Caco-2/TC7 intestinal epithelial model, reorganize the actin cytoskeleton, invade the target cells and translocate across the epithelium. The behaviour of these two strains was compared to that of the well known opportunistic pathogen P. aeruginosa PAO1.

Results

Both strains of P. fluorescens were found to decrease the transepithelial resistance (TER) of Caco-2/TC7 differentiated monolayers. This was associated with an increase in paracellular permeability and F-actin microfilaments rearrangements. Moreover, the invasion and translocation tests demonstrated that the two strains used in this study can invade and translocate across the differentiated Caco-2/TC7 cell monolayers.

Conclusions

The present work shows for the first time, that P. fluorescens is able to alter the intestinal epithelial barrier function by disorganizing the F-actin microfilament network. Moreover, we reveal that independently of their origins, the two P. fluorescens strains can translocate across differentiated Caco-2/TC7 cell monolayers by using the transcellular pathway. These findings could, at least in part, explain the presence of the P. fluorescens specific I2 antigen in the serum of patients with Crohn's disease.     

Effects of exogenous agmatine in human leukemia HMC-1 and HL-60 cells on proliferation, polyamine metabolism and cell cycle

Impairment of agmatine homeostasis is involved in the regulation of cell proliferation in malignant solid tumors. The present study aimed at analyzing the relevance of agmatine homeostasis in pathophysiology of human leukemia. Proliferation of the human leukemia cells HMC-1 and HL-60 was determined in the absence or presence of agmatine. Apoptosis and cell cycle distribution was investigated by determination of caspase-3 activity and/or flow cytometry after staining with propidium iodide. Expression analysis was performed by qPCR and by a microarray genechip. Exogenous agmatine inhibited proliferation of both HMC-1 and HL-60 cells. The antiproliferative effect was due to interference of agmatine with the cell cycle with no evident signs of apoptosis. Comparative analysis of expression of mRNA in untreated HMC-1 cells and in non-leukemic human mast cells revealed a much lower expression of agmatinase and diamine oxidase in HMC-1 cells indicating a significantly reduced agmatine catabolism in the leukemic cells. At the mRNA level, inhibition of proliferation of both cell lines by agmatine was associated with cell type-specific alterations of the expression of enzymes of the polyamine pathway. The present results point to a significant role of agmatine homeostasis in the (patho)physiology of cell proliferation of leukemic cells, at least in HMC-1 and HL-60 cells, that may serve as a potential target for an adjuvant therapy in the treatment of human leukemia.     

Investigation of the effects of the novel anticonvulsant compound carisbamate (RWJ-333369) on rat piriform cortical neurones in vitro

Background and purpose:

Carisbamate is being developed for adjuvant treatment of partial onset epilepsy. Carisbamate produces anticonvulsant effects in primary generalized, complex partial and absence-type seizure models, and exhibits neuroprotective and antiepileptogenic properties in rodent epilepsy models. Phase IIb clinical trials of carisbamate demonstrated efficacy against partial onset seizures; however, its mechanisms of action remain unknown. Here, we report the effects of carisbamate on membrane properties, evoked and spontaneous synaptic transmission and induced epileptiform discharges in layer II-III neurones in piriform cortical brain slices.

Experimental approach:

Effects of carisbamate were investigated in rat piriform cortical neurones by using intracellular electrophysiological recordings.

Key results:

Carisbamate (50–400 µmol·L⁻¹) reversibly decreased amplitude, duration and rise-time of evoked action potentials and inhibited repetitive firing, consistent with use-dependent Na⁺ channel block; 150–400 µmol·L⁻¹ carisbamate reduced neuronal input resistance, without altering membrane potential. After microelectrode intracellular Cl⁻ loading, carisbamate depolarized cells, an effect reversed by picrotoxin. Carisbamate (100–400 µmol·L⁻¹) also selectively depressed lateral olfactory tract-afferent evoked excitatory synaptic transmission (opposed by picrotoxin), consistent with activation of a presynaptic Cl⁻ conductance. Lidocaine (40–320 µmol·L⁻¹) mimicked carisbamate, implying similar modes of action. Carisbamate (300–600 µmol·L⁻¹) had no effect on spontaneous GABA_A miniature inhibitory postsynaptic currents and at lower concentrations (50–200 µmol·L⁻¹) inhibited Mg²⁺-free or 4-aminopyridine-induced seizure-like discharges.

Conclusions and implications:

Carisbamate blocked evoked action potentials use-dependently, consistent with a primary action on Na⁺ channels and increased Cl⁻ conductances presynaptically and, under certain conditions, postsynaptically to selectively depress excitatory neurotransmission in piriform cortical layer Ia-afferent terminals.     

精油对5-氟脲嘧啶渗透大鼠皮肤的促进作用

以月桂氮艹卓酮为参照研究了桉叶油、薄荷油和松节油3种精油对5-氟脲嘧啶渗透大鼠皮肤的促进作用及其机理。3种精油均具有促渗效果,其中桉叶油的增渗约60倍,而薄荷油和松节油分别引起46倍和28倍的增加,通过蒸馏分级将桉叶油按沸点高低分为5个部分,随着沸点升高,促渗效果也提高。在真空条件下140℃时的组分增渗倍数为83倍,略低于月桂氮艹卓酮(89倍)。精油的促渗作用可能与改进药物在组织中的分配和改进药物在皮肤中的扩散有关,但以改善扩散为主。3种精油改善扩散的程度与月桂氮艹卓酮相近。高沸点的桉叶油组分有类似的促渗机理。     

Muscle fiber dysfunction contributes to weakness in inclusion body myositis

Atrophy and fatty infiltration are important causes of muscle weakness in inclusion body myositis (IBM). Muscle weakness can also be caused by reduced specific force; i.e. the amount of force generated per unit of residual muscle tissue. This study investigates in vivo specific force of the quadriceps and ex vivo specific force of single muscle fibers in patients with IBM. We included 8 participants with IBM and 12 healthy controls, who all underwent quantitative muscle testing, quantitative MRI of the quadriceps and paired muscle biopsies of the quadriceps and tibialis anterior. Single muscle fibers were isolated to measure muscle fiber specific force and contractile properties. Both in vivo quadriceps specific force and ex vivo muscle fiber specific force were reduced. Muscle fiber dysfunction was accompanied by reduced active stiffness, which reflects a decrease in the number of attached actin-myosin cross-bridges during activation. Myosin concentration was reduced in IBM fibers. Because reduced specific force contributes to muscle weakness in patients with IBM, therapeutic strategies that augment muscle fiber strength may provide benefit to patients with IBM.     

The management of benign salivary disease: a case series

There are many causes for benign salivary gland disease but the most common relate to inflammation and infection. This usually revolves around duct obstruction and a reduction in the normal salivary flow from the gland into the mouth. This leads to retention of saliva, proximal to the obstruction and ascending infection from the mouth, usually because of the decrease in salivary flow. The increase in tension behind the obstruction causes significant pain and swelling, along with the inevitable infection if the obstruction is not relieved. This paper discusses the various treatments available for benign salivary gland disease, the traditional methods of treatment through to the use of endoscopic techniques which are currently available, including a discussion about the use of sialoendoscopy.