Kenneth B. Fallon

Poly(ADP-Ribose) Polymerase Inhibition Reduces Atherosclerotic Plaque Size and Promotes Factors of Plaque Stability in Apolipoprotein E–Deficient Mice Effects on Macrophage Recruitment, Nuclear Factor-κB Nuclear Translocation, and Foam Cell Death

Background— Poly(ADP-ribose) polymerase (PARP) was suggested to play a role in endothelial dysfunction that is associated with a number of cardiovascular diseases. We hypothesized that PARP may play an important role in atherogenesis and that its inhibition may attenuate atherosclerotic plaque development in an experimental model of atherosclerosis. Methods and Results— Using a mouse (apolipoprotein E [ApoE]−/−) model of high-fat diet–induced atherosclerosis, we demonstrate an association between cell death and oxidative stress–associated DNA damage and PARP activation within atherosclerotic plaques. PARP inhibition by thieno[2,3-c]isoquinolin-5-one reduced plaque number and size and altered structural composition of plaques in these animals without affecting sera lipid contents. These results were corroborated genetically with the use of ApoE−/− mice that are heterozygous for PARP-1. PARP inhibition promoted an increase in collagen content, potentially through an increase in tissue inhibitor of metalloproteinase-2, and transmigration of smooth muscle cells to intima of atherosclerotic plaques as well as a decrease in monocyte chemotactic protein-1 production, all of which are markers of plaque stability. In PARP-1−/− macrophages, monocyte chemotactic protein-1 expression was severely inhibited because of a defective nuclear factor-&kgr;B nuclear translocation in response to lipopolysaccharide. Furthermore, PARP-1 gene deletion not only conferred protection to foam cells against H2O2-induced death but also switched the mode of death from necrosis to apoptosis. Conclusions— Our results suggest that PARP inhibition interferes with plaque development and may promote plaque stability, possibly through a reduction in inflammatory factors and cellular changes related to plaque dynamics. PARP inhibition may prove beneficial for the treatment of atherosclerosis.

Poly(ADP-ribose) polymerase-1 inhibition prevents eosinophil recruitment by modulating Th2 cytokines in a murine model of allergic airway inflammation: a potential specific effect on IL-5.

We recently used a murine model of allergic airway inflammation to show that poly(ADP-ribose) polymerase-1 (PARP-1) plays an important role in the pathogenesis of asthma-related lung inflammation. In this study, we show that PARP-1 inhibition, by a novel inhibitor (TIQ-A) or by gene deletion, prevented eosinophilic infiltration into the airways of OVA-challenged mice. Such impairment of eosinophil recruitment appeared to take place after IgE production. OVA challenge of wild-type mice resulted in a significant increase in IL-4, IL-5, IL-10, IL-13, and GM-CSF secretions. Although IL-4 production was moderately affected in OVA-challenged PARP-1−/− mice, the production of IL-5, IL-10, IL-13, and GM-CSF was completely inhibited in ex vivo OVA-challenged lung cells derived from these animals. A single TIQ-A injection before OVA challenge in wild-type mice mimicked the latter effects. The marked effect PARP-1 inhibition exerted on mucus production corroborated the effects observed on the Th2 response. Although PARP-1 inhibition by gene knockout increased the production of the Th1 cytokines IL-2 and IL-12, the inhibition by TIQ-A exerted no effect on these two cytokines. The failure of lung cells derived from OVA-challenged PARP-1−/− mice to synthesize GM-CSF, a key cytokine in eosinophil recruitment, was reestablished by replenishment of IL-5. Furthermore, intranasal administration of IL-5 restored the impairment of eosinophil recruitment and mucus production in OVA-challenged PARP-1−/− mice. The replenishment of either IL-4 or IgE, however, did not result in such phenotype reversals. Altogether, these results suggest that PARP-1 plays a critical role in eosinophil recruitment by specifically regulating the cascade leading to IL-5 production.

Constitutive Activation of the Neuregulin-1/erbB Signaling Pathway Promotes the Proliferation of a Human Peripheral Neuroepithelioma Cell Line

Neuregulin-1 (NRG-1) proteins, acting through their erbB receptors, promote the differentiation, survival and/or proliferation of many cell types in the developing nervous system, including neural crest cells and neural crest-derived Schwann cells. We have recently found that the proliferation of a neoplastic Schwann cell line is dependent on constitutive activation of the NRG-1/erbB signaling pathway and that overexpression of NRG-1 in myelinating Schwann cells induces the formation of malignant peripheral nerve sheath tumors. These observations suggested that NRG-1 might similarly promote mitogenesis in a variety of neural neoplasms including peripheral neuro-epitheliomas, aggressive neural crest-derived neoplasms that arise in nerves and soft tissues. To test this hypothesis, we examined the expression of NRG-1 and its erbB receptors in SK-N-MC neuroepithelioma cells. SK-N-MC cells expressed multiple NRG-1 proteins and mRNAs encoding several α and β isoforms from the sensory and motor neuron-derived factor NRG-1 subfamily as well as the NRG-1 receptor subunits erbB2, erbB3, and erbB4. The erbB receptors expressed by SK-N-MC cells were constitutively tyrosine phosphorylated and inhibiting these kinases with the erbB specific inhibitor PD158780 reduced SK-N-MC DNA synthesis in a dose-dependent manner. We conclude that constitutive activation of the NRG-1/erbB signaling pathway promotes the proliferation of SK-N-MC neuroepithelioma cells in vitro and hypothesize that NRG-1/erbB autocrine, paracrine or juxtacrine signaling may contribute to the development and/or progression of neuroepitheliomas in vivo.

Atherosclerotic plaque-like lesions in synthetic arteriovenous grafts: implications for atherogenesis

Atherosclerotic plaque-like lesions are prevalent in synthetic arteriovenous shunts created to provide vascular access for hemodialysis. Similarities to atherosclerotic plaques in native arteries include eccentric location, immunoreactivity for smooth muscle actin, dystrophic calcifications, superimposed thrombi, and foam cells. Fatty streaks were not grossly identified on Sudan IV staining. Because of the similarities to atherosclerosis in native vessels, these findings may have several implications for atherogenesis. The development of raised, fibrous lesions does not require decades. The presence of smooth muscle in atherosclerotic plaque-like lesions does not require a source from tunica media. A precursor fatty streak may not be required for the development of raised, fibrous lesions. Finally, development of atherosclerotic plaque-like lesions does not require putative inflammatory effects from cholesterol or LDL accumulation, or even a native vessel that can respond to injury. The atherosclerotic plaque-like lesions in this study probably developed from organization of mural thrombi.

Intrinsic resistance to apoptosis of colon epithelial cells is a potential determining factor in the susceptibility of the A/J mouse strain to dimethylhydrazine-induced colon tumorigenesis.

Alterations in the delicate balance between cell proliferation and cell death disrupt colon homeostasis and serve as determining factors in colon tumorigenesis. The two mouse strains, AKR/J (resistant) and A/J (susceptible), have been widely used as models for dimethylhydrazine‐induced colon tumorigenesis. This study examined whether the differential susceptibilities of the two mouse strains to the tumorigenic effect of dimethylhydrazine were associated with intrinsic differences in the apoptotic machinery of the colon epithelial cells. While acute exposure to dimethylhydrazine caused massive apoptosis of colon epithelial cells in AKR/J mice, the effect was considerably less in A/J mice. Apoptosis in AKR/J mice occurred not only in the luminal side of the mucosa but also deep in the colonic crypts. In addition, this apoptosis appeared to involve caspase‐3. The increased sensitivity of AKR/J to dimethylhydrazine was associated with a persistent expression of tumor necrosis factor (TNF) but not of its receptors. After establishing a new method for isolating primary colon epithelial cells, we determined that cells derived from A/J mice were substantially more resistant to apoptosis in response to dimethylhydrazine or to a combination of TNF, cyclohexamide, and butyrate compared to cells from AKR/J mice. These results strongly suggest that a higher intrinsic resistance to apoptosis of colon epithelial cells may be an important determinant of predisposition to colon tumorigenesis in the A/J mouse strain.

ICAD deficiency in human colon cancer and predisposition to colon tumorigenesis: linkage to apoptosis resistance and genomic instability.

We previously showed that DNA fragmentation factor, which comprises a caspase-3-activated DNase (CAD) and its inhibitor (ICAD), may influence the rate of cell death by generating PARP-1-activating DNA breaks. Here we tested the hypothesis that ICAD-deficient colon epithelial cells exhibiting resistance to death stimuli may accumulate additional genetic modifications, leading to a tumorigenic phenotype. We show that ICAD deficiency may be associated with colon malignancy in humans. Indeed, an examination of ICAD expression using immunohistochemistry in an array of both colon cancer and normal tissues revealed that ICAD expression levels were severely compromised in the cancerous tissues. Upon DNA damage caused by a low dose of irradiation, ICAD cells acquire a tumorigenic phenotype. Colon epithelial cells derived from ICAD mice showed a significant resistance to death induced by the colon carcinogen dimethylhydrazine in vitro and in mice. Such resistance was associated with a decrease in PARP-1 activation. In an animal model of dimethylhydrazine-induced colon tumorigenesis, ICAD−/− mice developed significantly higher numbers of tumors with markedly larger sizes than the wild-type counterparts. Interestingly, the phenotype of the ICAD−/− mice was not associated with a significant increase in the precancerous aberrant crypt foci suggesting a potential link to tumor progression rather than initiation. More importantly, ICAD deficiency was associated with severe genomic instability as assessed by array comparative genomic hybridization. Such genomic instability consisted most prominently of amplifications but with sizable deletions as compared to the wild-type counterparts affecting several cancer-related genes including RAF-1, GSN, LMO3, and Fzd6 independently of p53. Altogether, our results present a viable case for the involvement of ICAD deficiency in colon carcinogenesis and show that apoptosis and genomic instability may comprise the means by which such deficiency may contribute to the process of increasing susceptibility to carcinogen-induced tumorigenesis.

Isolated CNS Whipple disease with normal brain MRI and false-positive CSF 14-3-3 protein: a case report and review of the literature

Whipple disease (WD) is usually a systemic infectious disease that can have central nervous system (CNS) involvement. WD confined to the CNS is extremely rare and difficult to diagnose, but can be fatal if not treated in a timely fashion. We present the case of a 42‐year‐old man with a subacute dementia accompanied by a movement disorder consisting of progressive supranuclear gaze palsy, myoclonus, and ataxia. Our patient lacked the typical magnetic resonance imaging (MRI) findings reported with isolated CNS WD and had a false‐positive cerebrospinal fluid (CSF) 14‐3‐3 protein. The patient expired, and definitive diagnosis of isolated CNS WD was made by autopsy with characteristic macrophage accumulations found in the brain but not in the gastrointestinal tract. We examine the literature on isolated CNS WD and discuss how these previously unreported findings make a rare diagnosis even more challenging. The reported patient is the first in the literature with tissue diagnosis of isolated CNS WD in the setting of normal brain MRI and positive CSF 14‐3‐3 protein. Isolated CNS WD should be added to the list of considerations for a false‐positive CSF 14‐3‐3 protein. Even in the absence of typical MRI lesions, a patient with subacute progressive dementia, supranuclear gaze palsy, and other various neurologic abnormalities should have the diagnosis of isolated CNS WD considered.

Intravascular malignant lymphomatosis diagnosed in both skeletal muscle and nerve biopsies.

Intravascular malignant lymphomatosis (IML) is a lymphoma, usually of B-cell phenotype, confined to intravascular spaces. IML is a relatively rare disease that is usually diagnosed at autopsy. We report a biopsy-proven case and review 15 published cases that were diagnosed antemortem by muscle, nerve biopsy, or both.

Exudative Hemorrhagic Duodenitis as a Primary Event in a Child With Henoch-Schönlein Purpura

2 4-year-old girl had a history of an acute onset of severe generalized colicky abdominal pain, fever, oral ulcer, loody diarrhea, and melena for 7 days. An examination showed ever, and generalized abdominal tenderness without organoegaly. Her blood tests showed a white blood cell count of 6,400/mL3, a hemoglobin level of 11.8 mg/dL, a hematocrit evel of 34.2%, a platelet count of 122,000/mm3, a neutrophil evel of 80%, an albumin level 2.6, a sedimentation rate of 11 m/h, and a C-reactive protein level of 6.5 mg/dL. A stool ulture, Clostridium difficile toxin, and parasites were negative. A agnetic resonance image of the abdomen showed significant owel-wall thickening in the duodenum and jejunum with dematous changes and sloughing of the mucosa (Figure A). A outine upper endoscopy revealed marked hyperemia, friability, nd edema with focal exudates in duodenum (Figure B). olonoscopy and ileoscopy were normal. The histologic findngs showed mild esophagitis, normal gastric mucosa, crypt bscess formation and cryptitis, fibrinopurulent exudates, an ncrease in mixed primarily neutrophilic inflammatory infilrates, and diffuse submucosal hemorrhage of the duodenum Figure C). The patient responded well with methylpredisolone within 1 week. Eighteen days after her onset of the llness a group of petechial rash appeared on her buttocks and he posterior aspect of her legs and progressed to significant urpura. Henoch-Schonlein purpura (HSP) was diagnosed.

Late-Onset Cerebral Toxoplasmosis After Allogeneic Hematopoietic Stem Cell Transplantation

Patient: Male, 44 Final Diagnosis: Cerebral toxoplasmosis after HSCT Symptoms: Hemiparesis • muscle weakness Medication: — Clinical Procedure: — Specialty: Hematology Objective: Unusual clinical course Background: Toxoplasmosis is an uncommon but potentially fatal complication following allogeneic hematopoietic stem cell transplantation (HCT). Post-transplant toxoplasmosis is often a reactivation of prior infection and typically occurs within the first 6 months of transplant. Herein, we report that cerebral toxoplasmosis may occur 22 months after allogeneic hematopoietic stem cell transplantation. Case Report: We describe a case of cerebral toxoplasmosis that occurred 22 months after an allogeneic HCT while the patient was on aerosolized pentamidine for Pneumocystis jiroveci pneumonia (PCP) prophylaxis. The disease was only diagnosed after brain biopsy because of atypical MRI appearance of the cerebral lesion and negative Toxoplasma gondii IgG antibody test result in the cerebrospinal fluid (CSF). The patient received pyrimethamine and sulfadiazine treatment, with dramatic improvement after several months. The patient is alive 2 years after infection diagnosis, with no evidence of disease and is off Toxoplasma prophylaxis. Conclusions: Cerebral toxoplasmosis can occur late after allogeneic HCT while patients are on immunosuppression therapy, with atypical features on imaging studies and negative Toxoplasma gondii IgG antibody test result in the CSF. Pre-transplant serologic screening for T. gondii antibodies in allogeneic transplant candidates is warranted. Brain biopsy can be a helpful diagnostic tool for cerebral lesions.