Multidrug resistance-associated transporter 2 regulates mucosal inflammation by facilitating the synthesis of hepoxilin A3

Neutrophil transmigration across mucosal surfaces contributes to dysfunction of epithelial barrier properties, a characteristic underlying many mucosal inflammatory diseases. Thus, insight into the directional movement of neutrophils across epithelial barriers will provide important information relating to the mechanisms of such inflammatory disorders. The eicosanoid hepoxilin A(3), an endogenous product of 12-lipoxygenase activity, is secreted from the apical surface of the epithelial barrier and establishes a chemotactic gradient to guide neutrophils from the submucosa across epithelia to the luminal site of an inflammatory stimulus, the final step in neutrophil recruitment. Currently, little is known regarding how hepoxilin A(3) is secreted from the intestinal epithelium during an inflammatory insult. In this study, we reveal that hepoxilin A(3) is a substrate for the apical efflux ATP-binding protein transporter multidrug resistance-associated protein 2 (MRP2). Moreover, using multiple in vitro and in vivo models, we show that induction of intestinal inflammation profoundly up-regulates apical expression of MRP2, and that interfering with hepoxilin A(3) synthesis and/or inhibition of MRP2 function results in a marked reduction in inflammation and severity of disease. Lastly, examination of inflamed intestinal epithelia in human biopsies revealed up-regulation of MRP2. Thus, blocking hepoxilin A(3) synthesis and/or inhibiting MRP2 may lead to the development of new therapeutic strategies for the treatment of epithelial-associated inflammatory conditions.

Salmonella enterica serovar Typhimurium modulates P-glycoprotein in the intestinal epithelium

Studies over the last decade have shown that Salmonella enterica serovar Typhimurium (S. typhimurium) is able to preferentially locate to sites of tumor growth and modulate (shrink) the growth of many cancers. Given this unique association between S. typhimurium and cancer cells, the objective of this study was to investigate the capacity of this microorganism to modulate the plasma membrane multidrug resistance (MDR) protein P-glycoprotein (P-gp), an ATP-binding cassette transporter responsible for effluxing many cancer drugs. Using an in vitro model of S. typhimurium infection of polarized human cancer intestinal cell lines, we have found that this enteric pathogen functionally downregulates the efflux capabilities of P-gp. Specifically, we show that S. typhimurium infection of human intestinal cancer cells results in the enhanced intracellular accumulation of a number of P-gp substrates that corresponds to the posttranscriptional downregulation of P-gp expression. Furthermore, cells expressing small interfering RNAs against MDR1, the gene encoding P-gp, were significantly more susceptible to the cytotoxic effects of bacterial infection. This result is consistent with our observation that S. typhimurium was significantly less able to invade cells overexpressing MDR1. Taken together, these results reveal a novel role for P-gp in the maintenance of homeostasis in the gastrointestinal tract in regard to bacterial infection. Thus the regulation of P-gp by S. typhimurium has important implications not only for the development of new cancer therapeutics aimed at reversing drug resistance but also in the understanding of how microbes have evolved diverse strategies to interact with their host.

A strategy to identify stable membrane-permeant peptide inhibitors of myosin light chain kinase

PURPOSE

A peptide inhibitor of myosin light chain kinase (MLCK), termed membrane permeant inhibitor of myosin light chain kinase (PIK), has previously been demonstrated to correct paracellular barrier defects associated with in vitro cell models of infectious and inflammatory intestinal disease. The current study describes a strategy to identify stable analogues of PIK required for future in vivo studies that has resulted in the identification of two promising candidates.

METHODS

Because PIK functions at an intracellular site of epithelial cells and is envisaged to be administered orally, hydrolysis patterns were determined for PIK in both extracts of homogenized Caco-2 (a human intestinal epithelial cell line) and in luminal secretions isolated from rat intestine. Based on these hydrolysis patterns, four peptides Ac-RKKYKYRRK-NH(2) (acetylated PIK), rkkykyrrk-NH(2) (D PIK), krrykykkr-NH(2) (Dreverse PIK), and RKKykyRRK-NH(2) (Dpalindrome PIK) were synthesised. Studies were carried out to determine the stability, activity, and selectivity of these PIK analogues.

RESULTS

D PIK and Dreverse PIK had much longer half-lives of 3.6 and 13.4 h, respectively, compared to PIK, acetylated (Ac)-PIK, or Dpalindrome PIK. All PIK analogues inhibited MLCK potently, although D PIK was a slightly better inhibitor than the other analogues. Similarly, all PIK analogues enhanced paracellular barrier function in Caco-2 monolayers studied in vitro. No appreciable inhibition of cAMP-dependent protein kinase (PKA) or calcium/calmodulin-dependent protein kinase II (CaMPKII) was detected with any of the analogues.

CONCLUSIONS

PIK is quickly degraded within two enzyme-containing preparations that represent different aspects of the intestinal environment. The PIK analogues D PIK and Dreverse PIK demonstrated extended half-lives in these enzyme preparations while retaining the biological activity and specificity of the parent PIK peptide.

Regulation of intestinal epithelial function: a link between opportunities for macromolecular drug delivery and inflammatory bowel disease

The intestinal epithelium performs a multitude of tasks related to digestion and homeostasis. As a consequence of ingestion, this tissue must also participate in activities associated with protecting the body from potential pathogenic agents and toxic materials. To efficiently perform tasks associated with digestion and these protective functions, the intestinal epithelium has established several anatomical, biochemical and physiological barriers to impede unregulated uptake of materials. In order to perform functions of digestion and homeostasis, the intestinal epithelium uses mechanisms that allow dynamic modulation of regulated uptake pathways that can respond rapidly to changes in diet, health and challenges from pathogenic agents and macromolecules. This review focuses on specific, recent advances made in understanding cellular pathways and mechanisms that regulate dynamic processes of these barriers and examines the feasibility of drug delivery strategies focusing on macromolecular therapeutics potentially useful in the treatment of inflammatory bowel disease (IBD).

Polymorphonuclear Cell Transmigration Induced byPseudomonas aeruginosaRequires the Eicosanoid Hepoxilin A3

Lung inflammation resulting from bacterial infection of the respiratory mucosal surface in diseases such as cystic fibrosis and pneumonia contributes significantly to the pathology. A major consequence of the inflammatory response is the recruitment and accumulation of polymorphonuclear cells (PMNs) at the infection site. It is currently unclear what bacterial factors trigger this response and exactly how PMNs are directed across the epithelial barrier to the airway lumen. An in vitro model consisting of human PMNs and alveolar epithelial cells (A549) grown on inverted Transwell filters was used to determine whether bacteria are capable of inducing PMN migration across these epithelial barriers. A variety of lung pathogenic bacteria, including Klebsiella pneumoniae, Escherichia coli, and Pseudomonas aeruginosa are indeed capable of inducing PMN migration across A549 monolayers. This phenomenon is not mediated by LPS, but requires live bacteria infecting the apical surface. Bacterial interaction with the apical surface of A549 monolayers results in activation of epithelial responses, including the phosphorylation of ERK1/2 and secretion of the PMN chemokine IL-8. However, secretion of IL-8 in response to bacterial infection is neither necessary nor sufficient to mediate PMN transepithelial migration. Instead, PMN transepithelial migration is mediated by the eicosanoid hepoxilin A3, which is a PMN chemoattractant secreted by A549 cells in response to bacterial infection in a protein kinase C-dependent manner. These data suggest that bacterial-induced hepoxilin A3 secretion may represent a previously unrecognized inflammatory mechanism occurring within the lung epithelium during bacterial infections.

Identification of hepoxilin A3 in inflammatory events: a required role in neutrophil migration across intestinal epithelia

The mechanism by which neutrophils [polymorphonuclear leukocyte (PMNs)] are stimulated to move across epithelial barriers at mucosal surfaces has been basically unknown in biology. IL-8 has been shown to stimulate PMNs to leave the bloodstream at a local site of mucosal inflammation, but the chemical gradient used by PMNs to move between adjacent epithelial cells and traverse the tight junction at the apical neck of these mucosal barriers has eluded identification. Our studies not only identify this factor, previously termed pathogen-elicited epithelial chemoattractant, as the eicosanoid hepoxilin A(3) (hepA(3)) but also demonstrate that it is a key factor promoting the final step in PMN recruitment to sites of mucosal inflammation. We show that hepA(3) is synthesized by epithelial cells and secreted from their apical surface in response to conditions that stimulate inflammatory events. Our data further establish that hepA(3) acts to draw PMNs, via the establishment of a gradient across the epithelial tight junction complex. The functional significance of hepA(3) to target PMNs to the lumen of the gut at sites of inflammation was demonstrated by the finding that disruption of the 12-lipoxygenase pathway (required for hepA(3) production) could dramatically reduce PMN-mediated tissue trauma, demonstrating that hepA(3) is a key regulator of mucosal inflammation.

Stereospecific chemical and enzymatic stability of phosphoramidate triester prodrugs of d4T in vitro

The phosphoramidate triester prodrug approach is widely used to deliver nucleotide forms of nucleoside analogues into target cells. We investigated the stereoselective stability of a series of prodrugs of the anti-HIV agent 2',3'-didehydro-2',3'-dideoxythymidine (d4T). Chemical stability was evaluated in phosphate buffer at pH values of biological relevance (i.e. pH 2.0, 4.6, 7.4). Enzymatic stability was tested in human plasma, in Caco-2 cell homogenates and monolayers and in rat liver. The compounds were relatively stable to chemical hydrolysis. Between 50 and 70% of unchanged prodrug was recovered after 16h incubation in human plasma, with no stereoselective preference for phosphate diastereoisomers. The p-OMe phenyl derivative, however, was an exception and only 5% of one diastereoisomer was recovered. In Caco-2 cells the stability and stereoselectivity largely depended on the experimental conditions: high enzymatic activity and stereoselectivity was observed in cell homogenates, but not in monolayers. In rat liver S9 fractions the stability profile was similar to that in Caco-2 cells and carboxyl ester cleavage appeared to be the sole mechanism of degradation in both media. The large and unpredictable differences in stereoselective metabolic rate of the pronucleotide series here presented suggest that in vivo circulating levels of intact prodrug could exert profoundly different activity or toxicity due to preferential body distribution of one diastereoisomeric form.

Stereoselective and Concentration-Dependent Polarized Epithelial Permeability of a Series of Phosphoramidate Triester Prodrugs of d4T: An in Vitro Study in Caco-2 and Madin-Darby Canine Kidney Cell Monolayers

Nucleoside analogs are successful, widely used antiviral and anticancer therapeutics. Nucleotide prodrugs (i.e., pronucleotide) have increasingly been used to improve in vivo efficacy of nucleoside analogs. In this study, we evaluated the permeability of a series of phosphoramidate triester prodrugs of the anti-HIV drug 2',3'-didehydro-2',3'-dideoxythymidine across monolayers of Caco-2, Madin-Darby canine kidney (MDCKII) epithelial cell line, and its recombinant clone containing the human MDR1/P-gp gene (MDR1-MDCKII). Transport was studied in the apical-to-basolateral (A-B) and the basolateral-to-apical directions (B-A). The impact upon transport of differences in stereochemistry at the chiral phosphate center was evaluated. In the Caco-2 and MDCK models the A-B permeability was lower than expected based on the lipophilicity of the compounds, suggesting the involvement of a polarized efflux system and/or metabolic degradation in limiting the absorption of these ester-based prodrugs. Average permeability values through cell monolayers obtained in the A-B direction were lower than in the B-A direction. The inclusion of the P-glycoprotein (P-gp) inhibitor verapamil in the transport medium markedly increased the permeability in the A-B direction, whereas decreasing it in the opposite direction, suggesting an efflux mechanism mainly mediated by P-gp. Stereoselective permeability was significant for the most lipophilic compounds, where the diastereoisomer possessing the slower eluting time on a reverse-phase high-performance liquid chromatography column was transported through Caco-2 and MDCK monolayers at higher rate.

Alkyloxyphenyl furano pyrimidines as potent and selective anti-VZV agents with enhanced water solubility

We have previously reported bicyclic furanopyrimidines as potent and selective inhibitors of varicella zoster virus (VZV) with subnanomolar activity for p-alkylphenyl substituted analogues. These compounds are highly lipophilic and of limited water solubility. In an effort to address this issue, and with a view to oral dosing, we have sought to enhance water solubility whilst retaining high antiviral potency and we herein report a novel series of p-alkyloxyphenyl compounds which contain a phenolic ether atom intended to boost hydrophilicity. We report the synthesis, characterisation and antiviral evaluation of this series and note the retention of extremely high antiviral potency, with EC50 values as low as 1 nanomolar.

Removal of tumours of the orbital apex via a postero-lateral orbitotomy

BACKGROUND

The surgical management of pure apical tumours of the orbit may be problematic with traditional approaches. A postero-lateral approach, specifically designed for apical growths, provides a more favourable angle of vision through a relatively small bone opening.

METHODS

A series of 103 consecutive cases of intraorbital tumours, operated on in a community-based institution, was retrospectively reviewed. Out of this series, 8 patients, harbouring lesions located in the posterior intraconal space, underwent a postero-lateral orbitotomy. This approach, through a small opening on the orbital and temporal portions of the greater wing of the sphenoid, with the lesser sphenoidal wing, the orbital plate of the frontal bone, the lateral rim of the orbit being maintained intact, allowed adequate exposure of the orbital apex and successful extirpation of the tumours. In four patients the histological examination disclosed a cavernoma; the other patients had, respectively, a dermoid cyst, a lymphoma, a hemangiopericytoma and a metastatic melanoma.

RESULTS

No recurrences were observed in a follow-up period ranging from 1 to 7 years postoperatively (the patient with melanoma died 16 months after operation for systemic complications of her illness). One patient showed transient weakness of lateral rectus muscle due to surgical manipulation, which subsided in few months.

CONCLUSIONS

The postero-lateral orbitotomy represents a reliable alternative to other traditional surgical approaches when dealing with tumours of the orbital apex, providing excellent exposure of this region with a low rate of operative morbidity.

Fibrotic-haemorrhagic reaction to synthetic dural substitute

A case is presented in which a patient developed a complication related to the use of Silastic dural substitute. Ten years after the initial surgery, a fibrotic-haemorrhagic reaction around the graft material was found, mimicking a recurrent meningioma clinically and radiologically. A review of the literature and suggested mechanisms of these complications are reported.

Infratentorial ischaemia following experimental cerebellar haemorrhage in the rat

Early changes of cerebellar and cerebral blood flow, as well as subsequent infratentorial ischaemia, were evaluated in an experimental model of cerebellar haemorrhage. Eight anaesthetized male adult Sprague-Dawley rats received an injection of autologous arterial blood (50 microliters) into the right cerebellar hemisphere. Eight animals were sham-operated and served as controls. Cerebellar blood flow, measured at regular time intervals in the hemispheric cortex ipsilateral to the lesion by the hydrogen clearance method, was significantly depressed in the experimental group as compared with the control animals. This drop in cerebellar blood flow was evident 5, 30, 60, 90, and 120 min postoperatively, with a return to pre-injection values recorded 180 min after surgery. No significant difference in supratentorial blood flow was detected over the entire period examined between the two groups of animals. Enzyme histochemistry demonstrated areas of ischaemia around the clot and within the brain stem in animals with an intracerebellar haemorrhage at the end of the experiment. These results provided evidence of ischaemic damage within the infratentorial compartment after the induction of experimental cerebellar haemorrhage.

Metallic fragment embolization to the middle cerebral artery

A 25-year-old male was wounded accidentally in the neck by a metallic fragment, which penetrated his right carotid artery and migrated within the ipsilateral middle cerebral artery. Clinical and laboratory findings over a 16-month-period are reported. Problems arising from the presence of metallic emboli to the cerebral circulation are discussed on the basis of the pertinent literature.

Spinal subarachnoid hematoma of unknown etiology. A case report

A case of spinal subarachnoid hematoma at T3-T7 level is reported in a 60-year-old hunter, who developed progressive spinal cord impairment after receiving the recoil of his shotgun. Both clinical and neuroradiological investigations, including the selective spinal angiography, failed to demonstrate the origin of the bleeding. The combination of an apparently trivial spinal trauma with temporary increase of the intrathoracic pressure might be considered as possible etiologic factor.

Penetrating craniocerebral missile injuries in civilians: a retrospective analysis of 314 cases

Analysis of 314 cases of penetrating craniocerebral missile injuries in civilians revealed a high rate of early mortality, with 228 victims having died at the scene and a further 38 dead within 3 hours. Surgery was performed in 44 patients who had a preoperative Glasgow Coma Score of at least 4. Out of the 26 survivors, all operated upon, 19 had an adequate recovery (score of 0-3 on the expanded Glasgow Outcome Scale). Vigorous resuscitation and early surgery often resulted in useful survivals and occasionally in spectacular recoveries. However, the high mortality rate on the scene or soon after the injury restricted the possibility of effective management to a minority of cases.

Changes in infratentorial blood flow following experimental cerebellar haemorrhage. A preliminary report

The temporal progression of changes in blood flow within the hemispheric cerebellar cortex, following an experimental cerebellar ipsilateral haemorrhage, was investigated in rats by using the hydrogen clearance technique. Stereotactical injection of 50 microliters of fresh autologous blood into the paramedian white matter was found to produce an early drop of cerebellar blood flow, with subsequent rise toward higher values. An increase of the intracranial pressure only occurred at the time of injection of blood. Arterial blood gases, mean arterial blood pressure and blood glucose levels did not exhibit significant changes. Histochemical evaluations of glycogen phosphorylase showed a posthaemorrhagic pattern of enzyme depletion, consistent with the occurrence of an ischaemic damage in both the cerebellum and the brain stem.

Transient upper monoballism in the presence of contralateral chronic subdural hematoma

A case of chronic subdural hematoma associated with contralateral upper monoballism is reported. Intracranial midline shift and transtentorial herniation of the ipsilateral temporal lobe were the only demonstrated CT abnormalities. Complete neurological recovery followed the evacuation of the hematoma. Direct mechanical injury caused by the marked brain compression and distortion, and transient ischemic changes within cerebral areas whose damages may result in ballism, may be considered important causative factors of such an unusual neurological complication.

Gas bubbles within acute intracranial epidural haematomas

In order to assess the actual incidence of gas bubbles trapped within acute intracranial epidural haematomas, as revealed by computed tomography (CT) of the skull, a series of 204 patients with surgically verified epidural haematomas was retrospectively reviewed. Gas bubbles were observed on CT scan in 22.5% of the cases, with the incidence rising to 37% when CT scanners of the last generation were employed. The available data failed to demonstrate the actual source of intracranial gas. No correlation was found between the presence of gas bubbles and outcome. No patient in the whole series showed any sign of intracranial infection.

Parkinsonism in the presence of intracranial extracerebral haematomas

Bilateral Parkinsonism has been observed in a 60-year-old female with a chronic subdural intracranial haematoma. Scattered, poorly marginated, hypodense areas within the ipsilateral pallidus and putamen were evident on the preoperative CT scans. The rapid neurological improvement following the surgical drainage of the subdural clot and the evolution of the densitometric features of the nuclear lesions, which became clear-cut, though smaller, in the following months, suggest a cause-and-effect relation between the haematoma and the clinical symptomatology. To the best of our knowledge this is the first case in which anatomical lesions within the basal ganglia could be detected neuroradiologically.

Gunshot wounds of the brain in civilians

A consecutive series of 178 civilians with gunshot wounds of the brain was retrospectively analyzed. The overall mortality was 93%, with 88% of the victims having succumbed within 3 hours. Surgery was performed in 21 cases, all with a Glasgow Coma Score of 6 or more. Out of the 12 survivors, 9 exhibited minor neurological signs at the time of discharge. Good outcome occasionally resulted in patients with lesions crossing the midline, or affecting two lobes of a single hemisphere. Although spectacular recoveries in individual patients with apparently devastating injuries can be regarded as a sufficient basis for an aggressive approach, including vigorous resuscitation and early surgery, bleak possibilities still exist as to the management of civilian gunshot wounds, owing to the high mortality rate on the scene, or soon after the injury.

Axonal elongation into peripheral nerve grafts between thalamus and somatosensory cortex of the rat. An experimental model

After destruction of the thalamocortical projections of one side in 12 adult rats, the ipsilateral thalamic ventrobasal nucleus was connected with the contralateral somatosensory cortex through an autologous peripheral nerve graft. Three months after the implanting procedure, horseradish peroxidase was applied to the transected nerve. Retrograde labeling of cells occurred in all examined animals. Evidence of newly formed thalamocortical connections provides the experimental basis to a model suitable for functional evaluations.

Cerebral blood flow in minor cerebral contusion

Seventeen patients with minor cerebral contusion were selected from a series of patients with head injuries of various severity, who had undergone repeat evaluations of the regional cerebral blood flow. The mean global flow (expressed as mean global initial slope index) on early examination was found to be significantly lower, compared with that recorded in healthy volunteers. A tendency towards the recovery of higher flow values was apparent in repeat evaluations that were performed several weeks after the injury. Interhemispheric asymmetries of flow were a common occurrence, with lower perfusion and reduced attenuation values on computed tomography scans being, however, in good agreement only in approximately half of the cases.

Partial ventricular dilatation contralateral to chronic subdural haematoma

In a series of 88 cases of chronic subdural haematoma, the occurrence of dilatation of the posterior portion of the contralateral ventricle was found to be unrelated to any major neurological variable. There was, however, a prevalence of recurrences of the subdural effusions in the patients with partial hydrocephalus, compared with patients without ventricular dilatation.