Role of blood cell-associated angiotensin II type 1 receptors in the cerebral microvascular response to ischemic stroke during angiotensin-induced hypertension

BACKGROUND

Angiotensin II type 1 receptor (AT1R) blockers lower the incidence of ischemic stroke in hypertensive patients and attenuate brain inflammation and injury in animal models. Although AT1R on both blood cells (BC) and vascular endothelial cells (EC) can be activated by angiotensin II (Ang II) to elicit inflammation, little is known about the relative contributions of AT1R expressed on BC and EC to the brain injury responses to ischemia and reperfusion (I/R) in the setting of angiotensin-induced hypertension.

METHODS

The contributions of BC- and EC-associated AT1R to I/R-induced brain inflammation and injury were evaluated using wild type (WT), AT1aR-/-, and bone marrow chimera mice with either a BC+/EC+ (WT→WT) or BC-/EC+ (AT1aR-/-→WT) distribution of AT1aR. The adhesion of leukocytes and platelets in venules, blood brain barrier (BBB) permeability and infarct volume were monitored in postischemic brain of normotensive and Ang II-induced hypertensive mice.

RESULTS

The inflammatory (blood cell adhesion) and injury (BBB permeability, infarct volume) responses were greatly exaggerated in the presence of Ang II-induced hypertension. The Ang II-enhanced responses were significantly blunted in AT1aR-/- mice. A similar level of protection was noted in AT1aR-/- →WT mice for BBB permeability and infarct volume, while less or no protection was evident for leukocyte and platelet adhesion, respectively.

CONCLUSIONS

BC- and EC-associated AT1aR are both involved in the brain injury responses to ischemic stroke during Ang II-hypertension, with EC AT1aR contributing more to the blood cell recruitment response and BC AT1aR exerting a significant influence on the BBB disruption and tissue necrosis elicited by I/R.

Selectin-mediated recruitment of bone marrow stromal cells in the postischemic cerebral microvasculature

BACKGROUND AND PURPOSE

The therapeutic potential of bone marrow stromal cells (BMSCs) has been demonstrated in different models of stroke. Although it is well established that BMSCs selectively migrate to the site of brain injury, the mechanisms underlying this process are poorly understood. This study addresses the hypothesis that selectins mediate the recruitment of BMSCs into the postischemic cerebral microvasculature.

METHODS

Focal ischemic stroke was induced by middle cerebral artery occlusion and reperfusion. Cell recruitment was monitored using either fluorescent- or radiolabeled BMSCs detected by intravital microscopy or tissue radioactivity. Mice were treated with either a blocking antibody against P- or E-selectin or with the nonselective selectin antagonist, fucoidin. The role of CD44 in cell recruitment was evaluated using BMSCs from CD44 knockout mice.

RESULTS

Middle cerebral artery occlusion and reperfusion was associated with a significantly increased adhesion of BMSCs in cerebral venules compared with sham mice. Immunoneutralization of either E- or P-selectin blocked the middle cerebral artery occlusion and reperfusion-induced recruitment of adherent BMSCs. An attenuated recruitment response in the postischemic hemisphere was also noted after fucoidin treatment or administration of CD44-deficient BMSCs.

CONCLUSIONS

Cerebral vascular endothelium assume a proadhesive phenotype after ischemic stroke that favors the recruitment of BMSCs, which use both P- and E-selectin to home into the infarct site. CD44 may serve as the critical ligand for selectin-mediated BMSC recruitment.

JC virus-associated nephropathy in a renal transplant recipient and comparative analysis of previous cases

We report JC virus (JCV)-associated nephropathy in a renal allograft recipient and summarize the clinical and laboratory data of the 8 previous cases. A 28-year-old male renal allograft recipient received a preemptive transplant from his father. Six months later, a kidney biopsy was performed because of deterioration of allograft function. Biopsy revealed tubulointerstitial mononuclear infiltrates with normal glomeruli; on hematoxylin and eosin staining, basophilic nuclear inclusions were seen in the nucleus of tubular cells. Urinary cytology failed to demonstrate decoy cells, but polymerase chain reaction of a urinary sample was positive for JCV 3.15 × 10(10) copies/mL. Additionally, polyomavirus (SV40) immunohistochemical staining was performed and was positive in the enlarged nuclei of tubular epithelial cells in the kidney biopsy sample. After the diagnosis of polyomavirus-associated nephropathy (PVAN) was confirmed by kidney biopsy, immunosuppressive agents were reduced. Intravenous immunoglobulin was administered 5 times at a dose of 500 mg/kg every other 3 weeks. Two months after diagnosis, the serum creatinine became stable and urinary viral load of JCV was decreased. Because viruria was still present, tacrolimus was converted to sirolimus. Four months after immunosuppressive agent conversion from tacrolimus to sirolimus, the viruria had disappeared. Review of the literature and our case demonstrates that male gender, previous acute rejection episode, low incidence of JCV viremia, PVAN pattern B histology, and reducing immunosuppression are the diagnostic touchstones for PVAN due to JCV.

Induction of neuro-protective/regenerative genes in stem cells infiltrating post-ischemic brain tissue

BACKGROUND

Although the therapeutic potential of bone marrow-derived stromal stem cells (BMSC) has been demonstrated in different experimental models of ischemic stroke, it remains unclear how stem cells (SC) induce neuroprotection following stroke. In this study, we describe a novel method for isolating BMSC that infiltrate postischemic brain tissue and use this method to identify the genes that are persistently activated or depressed in BMSC that infiltrate brain tissue following ischemic stroke.

METHODS

Ischemic strokes were induced in C57BL/6 mice by middle cerebral artery occlusion for 1 h, followed by reperfusion. BMSC were isolated from H-2 Kb-tsA58 (immortomouse) mice, and were administered (i.v.) 24 h after reperfusion. At the peak of therapeutic improvement (14 days after the ischemic insult), infarcted brain tissue was isolated, and the BMSC were isolated by culturing at 33 degrees C. Microarray analysis and RT-PCR were performed to compare differential gene expression between naïve and infiltrating BMSC populations.

RESULTS

Z-scoring revealed dramatic differences in the expression of extracellular genes between naïve and infiltrating BMSC. Pair-wise analysis detected 80 extracellular factor genes that were up-regulated (>/= 2 fold, P < 0.05, Benjamini-Hochberg correction) between naïve and infiltrated BMSC. Although several anticipated neuroregenerative, nerve guidance and angiogenic factor (e.g., bFGF, bone morphogenetic protein, angiopoietins, neural growth factor) genes exhibited an increased expression, a remarkable induction of genes for nerve guidance survival (e.g., cytokine receptor-like factor 1, glypican 1, Dickkopf homolog 2, osteopontin) was also noted.

CONCLUSIONS

BMSC infiltrating the post-ischemic brain exhibit persistent epigenetic changes in gene expression for numerous extracellular genes, compared to their naïve counterparts. These genes are relevant to the neuroprotection, regeneration and angiogenesis previously described following stem cell therapy in animal models of ischemic stroke.

An evaluation of the tuberculin skin test for anti TNF alpha prophylaxis in patients with ankylosing spondylitis and rheumatoid arthritis

AIM

The tuberculin skin test (TST) has recently been proposed as a screening procedure for latent TB prior to anti-tumor necrosis factor (TNF) alpha therapy. Our aim was to evaluate TST levels in patients receiving anti TNF alpha due to ankylosing spondylitis (AS) and rheumatoid arthritis (RA).

MATERIALS AND METHODS

73 AS patients (52 male, 21 female) and 33 RA patients (11 male, 22 female) were enrolled in the study. Patients' clinical and demographic characteristics were recorded. Average age +/- standard deviation was 38.8 +/- 7.2 years for AS and 40.7 +/- 13 for RA. Median number of immunosuppressive agents used was 1 (min-max) (0-2) in AS and 2 (2-3) in RA. To determine the activity of the disease, BASDAI (Bath Ankylosing Spondylitis Disease Activity Index) was measured in AS patients, and DAS 28 (Disease Activity Index) was used in RA patients. TST was performed using the Mantoux method in all patients.

RESULTS

Mean BASDAI was 5.1 +/- 0.8 in AS, and DAS 28 score in RA was 5.7 +/- 0.5. Both, AS and RA patients had active disease. TST values were higher in AS than in RA patients. TST values were 11.5 +/- 6.5 mm in AS patients, compared to 7.0 +/- 6.4 mm in RA patients. A positive correlation between disease duration and TST was determined in AS patients. There was also a weak correlation in RA patients between immunosuppressive use and TST (r = 0.37, p = 0.032). No correlation was determined with disease activation in AS or RA patients.

CONCLUSION

This is the first study to evaluate the correlation between the use of multiple immunosuppressive agents and TST. We determined that TST is correlated with disease duration in AS and with the use of multiple immunosuppressive agents in RA (Tab. 3, Ref. 21).

Roles of inflammation and the activated protein C pathway in the brain edema associated with cerebral venous sinus thrombosis

BACKGROUND AND PURPOSE

Increased blood-brain barrier (BBB) permeability, brain edema, and hemorrhage are important consequences of cerebral venous sinus thrombosis (CVST). The objective of this study was to define the role of the protein C pathway in the BBB permeability and edema elicited by experimental CVST. The role of neutrophil recruitment was also evaluated.

METHODS

Edema, BBB permeability, leukocyte-endothelial cell adhesion (LECA) and inflammatory cytokine levels were monitored in a murine model of CVST. The role of activated protein C (APC) was assessed in wild type mice (WT) receiving APC neutralizing antibody and in endothelial protein C receptor overexpressing mice (EPCR-tg). Neutrophil involvement was evaluated using an anti-CD18 antibody (Ab) and antineutrophil serum.

RESULTS

Brain edema and increases in BBB permeability and LECA were noted 48 hours after CVST. APC immunoblockade exacerbated these responses, while EPCR-tg exhibited blunted responses, as did WT treated with either antineutrophil serum or the CD18 Ab.

CONCLUSIONS

The protein C pathway protects the brain against the deleterious microvascular responses to CVST, a response that appears to be linked to the recruitment of inflammatory cells.

Cardiovascular risk factors in hemodialysis and peritoneal dialysis patients

BACKGROUND

Cardiovascular disease (CVD) is the major cause of mortality and morbidity of hemodialysis (HD) and peritoneal dialysis (CAPD) patients. We aimed to investigate the cardiovascular risk factors and their correlation with CVD in groups of HD and CAPD patients.

METHODS

Thirty HD patients, 30 CAPD patients and 30 healthy controls were included in the study. Apolipoprotein A-l (apo A-l), apolipoprotein B (apo B), apolipoprotein(a) [Lp(a)] and high-sensitivity CRP (hs-CRP) were measured with a Beckman Coulter nephelometer, and homocysteine (Hcy) was determined with an Agilent HPLC analyzer. Lipid profile was determined with a Synchron LX 20 Pro analyzer.

RESULTS

Hcy levels were 41.9+/-19.4, 41.8+/-38.5 and 9.3+/-3.5 micromol/L; Lp(a) levels were 325+/-315, 431+/-367 and 130+/-97 mg/L; hs-CRP levels were 3.78+/-3.21, 4.34+/-3.39 and 2.07+/-1.67 mg/L; apo A1/apo B ratios were 1.46+/-0.6, 1.36+/-0.5 and 1.80+/-0.59; total cholesterol levels were 3.56+/-0.7, 4.84+/-1.1 and 4.39+/-0.5 mmol/L; triglycerides were 1.44+/-0.5, 1.60+/-0.8 and 0.85+/-0.5 mmol/L in the HD, CAPD and control groups, respectively.

CONCLUSION

HD and CAPD patients had higher Hcy, hs-CRP and Lp(a) levels and lower apo A/B ratios than controls. There was no significant difference between the HD and CAPD groups. Hypertension, age and hs-CRP showed a positive correlation with CVD.

Leukocyte recruitment and ischemic brain injury

Leukocytes are recruited into the cerebral microcirculation following an ischemic insult. The leukocyte-endothelial cell adhesion manifested within a few hours after ischemia (followed by reperfusion, I/R) largely reflects an infiltration of neutrophils, while other leukocyte populations appear to dominate the adhesive interactions with the vessel wall at 24 h of reperfusion. The influx of rolling and adherent leukocytes is accompanied by the recruitment of adherent platelets, which likely enhances the cytotoxic potential of the leukocytes to which they are attached. The recruitment of leukocytes and platelets in the postischemic brain is mediated by specific adhesion glycoproteins expressed by the activated blood cells and on cerebral microvascular endothelial cells. This process is also modulated by different signaling pathways (e.g., CD40/CD40L, Notch) and cytokines (e.g., RANTES) that are activated/released following I/R. Some of the known risk factors for cardiovascular disease, including hypercholesterolemia and obesity appear to exacerbate the leukocyte and platelet recruitment elicited by brain I/R. Although lymphocyte-endothelial cell and -platelet interactions in the postischemic cerebral microcirculation have not been evaluated to date, recent evidence in experimental animals implicate both CD4+ and CD8+ T-lymphocytes in the cerebral microvascular dysfunction, inflammation, and tissue injury associated with brain I/R. Evidence implicating regulatory T-cells as cerebroprotective modulators of the inflammatory and tissue injury responses to brain I/R support a continued focus on leukocytes as a target for therapeutic intervention in ischemic stroke.

Coexistence of different tissue tumourigenesis in an N-methyl-N-nitrosourea-induced mammary carcinoma model: a histopathological report in Sprague-Dawley rats

N-methyl- N-nitrosourea (MNU), a highly potent carginogen, is widely used to generate mammary tumours in murine species. In a model of MNU-induced mammary carcinogenesis using immature female Sprague-Dawley rats, large mammary tumours (largest dimension ≥0.5 cm) were obtained within a very short period of time. In addition, in the rats bearing MNU-induced mammary carcinomas, there were a number of tumours whose origins were not from mammary tissue but from several different tissues and from mammary non-epithelial tissue. The tumours were of mesenchymal or epithelial origin and they were located in the inguinal region. These tumours were diagnosed as fibroadenoma, combined tubular adenoma and fibroadenoma, hyperkeratotic papilloma, keratinous cyst and malignant peripheral nerve sheath tumour (MPNST) with smooth muscle differentiation. The occurrence of these other tumours in addition to the development of the mammary carcinomas may be attributed to a direct local effect of the intraperitoneal administration of MNU during the sexual development of the immature rats. In the MNU-induced mammary tumour model, coexistence of tumourigenesis in various non-mammary tissues should be considered an important factor that may interfere with experimental procedures and results and also the quality of life of the tumour-bearing animals.

Cell adhesion molecules and ischemic stroke

OBJECTIVE

To describe the role of adhesion molecules in ischemic stroke.

METHODS

A PubMed search of literature pertaining to this study was conducted in April 2008 using specific keyword search terms pertaining to stroke and various listed subtopics related to adhesion molecules.

RESULTS

An important contribution of beta2-integrins (CD11/CD18), intercellular adhesion molecule and P-selectin in the recruitment of leukocytes as well as platelets in the post-ischemic cerebral microvasculature has been defined in related studies. Immunoblockade or genetic deletion of these adhesion molecules has been shown to reduce infarct volume, edema, behavioral deficits and/or mortality in different animal models of ischemic stroke. Anti-adhesion agents also appear to widen the therapeutic window for thrombolytic therapy in these experimental models. An emerging role of inflammatory signaling pathways has also been addressed in modulating adhesion properties of post-ischemic cerebral microvasculature. Despite the promising data obtained from animal studies, few clinical trials assessing anti-adhesion therapy in ischemic stroke have failed to show efficacy.

DISCUSSION

Several experiments using cell surface adhesion molecules as targets of stroke therapy are promising yet inadequate. Clinical trials using immune blockade of adhesion molecules by antibodies have failed due to immune reactions of the host. Further clinical trials are needed to test the efficacy of humanized antibodies or non-immunogenic agents that interfere with cell adhesion mechanisms. Adhesion blocking strategies seem to be effective particularly at reperfusion and use of these strategies with thrombolytic therapies justifies a continued effort to define the role of adhesion molecules in the pathophysiology of cerebral ischemia-reperfusion.

Blood cell-derived RANTES mediates cerebral microvascular dysfunction, inflammation, and tissue injury after focal ischemia-reperfusion

BACKGROUND AND PURPOSE

Although chemokines have been implicated in cardiovascular diseases, few studies have addressed the role of these inflammatory mediators in ischemic stroke. This study tested the hypothesis that RANTES (CCL5; regulated on activation, normal T-cell expressed and secreted) mediates the cerebral microvascular dysfunction, inflammation, and tissue injury induced by brain ischemia and reperfusion.

METHODS

After 60-minute middle cerebral artery occlusion and reperfusion, the adhesion of leukocytes and platelets in cerebral venules, infarct volume, and blood-brain barrier permeability were measured in wild-type mice (WT), RANTES-deficient mice (RANTES(-/-)), WT mice transplanted with RANTES(-/-) bone marrow (RANTES>WT), and control bone marrow chimeras (WT>WT). The concentration of RANTES and several cytokines was also measured by enzyme-linked immunosorbent assay and a cytometric bead array.

RESULTS

The enhanced leukocyte and platelet adhesion, increased blood-brain barrier permeability, and tissue infarction elicited in WT and WT>WT mice after middle cerebral artery occlusion and reperfusion were significantly blunted in RANTES(-/-) mice. Similar attenuation of the middle cerebral artery occlusion and reperfusion-induced responses were noted in RANTES>WT chimeras. Although RANTES deficiency did not alter the changes in tissue cytokine levels elicited by middle cerebral artery occlusion and reperfusion, plasma concentrations interleukin-6, interleukin-10, and interleukin-12 were all reduced.

CONCLUSIONS

These findings implicate blood cell-derived RANTES in the microvascular, inflammatory, and tissue injury responses of the brain to ischemia and reperfusion.