Neuroinflammatory mechanisms of blood-brain barrier damage in ischemic stroke

As part of the neurovascular unit, the blood-brain barrier (BBB) is a unique, dynamic regulatory boundary that limits and regulates the exchange of molecules, ions, and cells between the blood and the central nervous system. Disruption of the BBB plays an important role in the development of neurological dysfunction in ischemic stroke. Blood-borne substances and cells have restricted access to the brain due to the presence of tight junctions between the endothelial cells of the BBB. Following stroke, there is loss of BBB tight junction integrity, leading to increased paracellular permeability, which results in vasogenic edema, hemorrhagic transformation, and increased mortality. Thus, understanding principal mediators and molecular mechanisms involved in BBB disruption is critical for the development of novel therapeutics to treat ischemic stroke. This review discusses the current knowledge of how neuroinflammation contributes to BBB damage in ischemic stroke. Specifically, we provide an updated overview of the role of cytokines, chemokines, oxidative and nitrosative stress, adhesion molecules, matrix metalloproteinases, and vascular endothelial growth factor as well as the role of different cell types in the regulation of BBB permeability in ischemic stroke.

Abstract 3253: Droplet digital PCR is a sensitive method for detecting refractory acute myeloid leukemia (AML) clones in peripheral blood and saliva

Droplet digital PCR (ddPCR) is a highly sensitive and rapid method for detecting mutant allele frequency (MAF). In preliminary work, our lower limit of detection for common myeloid gene mutations was 0.001% in peripheral blood and bone marrow compared to 0.1% with flow cytometry and 0.01% with real-time quantitative PCR, and turnaround time is 1 day. Furthermore, we detected leukemic mutant alleles in peripheral blood (PB), introducing the possibility of sparing painful bone marrow biopsy procedures to determine treatment response. Thus, we hypothesized that ddPCR is a feasible and accurate method for monitoring leukemic disease burden in PB for the prospective care of patients (pts) with AML. Eighteen patients (pts) with de novo, relapse/refractory, and secondary AML were recruited to an IRB-approved study (NCT02435550) and bone marrow (BM), peripheral blood (PB), and saliva were collected at standard clinical visits. Gene mutations were identified by whole-exome sequencing (WES) of BM specimens at study entry. For ddPCR interrogation, genomic DNA was isolated (Qiagen), and select primers and probes (Bio-Rad/IDT) were developed based on variants identified in WES data. Case-specific primers and probes were validated on archived specimens obtained at study entry. 12/18 pt mutanomes met criteria for primer/probe design. 8 pts are in the primer/probe design and validation stage and 4 have completed validation and serial analyses. WES identified, and ddPCR confirmed, at least 1 mutation per patient at the study entry timepoint. The mutations included NRAS G13R, NRAS G12A, CSF3R T618I, and IDH2 R172K. In 2 cases, we observed a reduction in both PB and saliva MAF that were consistent with the reduction in both BM and PB blasts after treatment, resulting in complete remissions. Although PB blasts were reduced in a third pt receiving ruxolitinib, the persistence of their CSF3R MAF in PB indicated a resistant AML clone. WES revealed the presence of NRAS G13R variant in a secondary AML pt; however, WES did not detect this NRAS G13R variant in a cryopreserved BM specimen obtained at the pts MDS diagnosis. Interestingly, ddPCR was able to detect NRAS G13R variant at 0.1% MAF in a PB sample obtained at MDS diagnosis, demonstrating the ultrasensitive detection of rare variants within a sample, and highlighting the subclonal evolution of this pt's malignancy. Rapid detection of myeloid-related somatic mutations in a variety of tissue sources (i.e., saliva, PB) will allow for noninvasive monitoring of AML tumor burden. ddPCR may be used to observe molecular response to treatment and to detect molecular residual disease and relapse prior to clinically indicated BM biopsies.

Citation Format: Kimberly E. Hawkins, Cesia Salan, Madeleine Turcotte, Lauren T. Vaughn, Mei Zhang, Yanping Zhang, Barry Sawicki, Glenda G. Anderson, Nosha Farhadfar, Hemant S. Murthy, Biljana N. Horn, Helen L. Leather, Paul Castillo, Maxim Norkin, John W. Hiemenz, Randy A. Brown, William Slayton, Jack W. Hsu, John R. Wingard, Christopher R. Cogle, Leylah M. Drusbosky. Droplet digital PCR is a sensitive method for detecting refractory acute myeloid leukemia (AML) clones in peripheral blood and saliva [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3253.

Abstract 4285: Genomics-driven clustering of disease-related biomarkers identifies therapeutic options in myelodysplastic syndromes (MDS)

Hypomethylating agents (HMA) and lenalidomide (LEN) are approved and used in the treatment of patients (pts) with MDS, though these drugs fail in most pts. No method exists to predict drug response beyond associating single actionable mutations with a single drug's response. We hypothesized that MDS pts can be clustered by similarities in genomic/molecular profiles, & that each cluster may be assigned combos of FDA-approved drugs to target their unique biomarker profile. Bone marrow cells from 88 MDS pts & the MDS-L cell line were analyzed by cytogenetics & for mutations in 14 myeloid genes using NGS. 31 pts had sufficient data for analysis. 20 profiles had similar aberrations & were grouped. Genomic data from pts and MDS-L were entered into a computational biology modeling (CBM) software, which generates a disease-specific protein network map using PubMed to create digital models and identify characteristic biomarkers unique to each pt. An algorithm was created to cluster the models based on overlapping disease-specific biomarkers. Digital drug simulations (DDS) were conducted both on MDS-L & pt simulation models by quantitatively measuring drug effect on a cell growth score (CGS), a composite of cell proliferation, viability & apoptosis. DDS identified drugs by assessing their impact on disease-specific biomarkers and calculated CGSs. Predictions were validated using MTT. 14/31 MDS pt profiles, including the MDS-L cell line, clustered into 4 groups based on biomarker characteristics.MDS-L cells harbor NRAS (G12A) mutation,-7,-12,+1,+8,+19,+20 and +21. Genes associated with increased copy number (CN) include AURKA, IGFR, PAR5, MTOR, IL6, JAK3, MDM4, MYC, MCL1, COX2, PDE4A, and RCE1; genes associated with decreased CN include DUSP1, RASA1, NR3C1, IRF1, ETV6, and SHH. CBM identified active biomarkers in MDS-L cells (90RSK, MAPK7, AKT and BTK), validated by western blot. DDS predicted nelfinavir+celecoxib to be effective in MDS-L. MDS-L cells were treated with nelfinavir, celecoxib, and nelfinavir+celecoxib with increasing doses. Nelfinavir & celecoxib reduced MDS-L viability in a dose-dependent manner, while nelfinavir+celecoxib showed additive reduction of MDS-L viability. DDS was performed on each pt to predict response to HMA and LEN. Two of the clusters (n=2/cluster) were predicted to be non-responders to any SOC therapy. A third cluster (n=3) was predicted to respond to HMA, but not LEN, and the fourth cluster (n=6) showed varying or no response to either HMA/LEN. These results use a novel concept of using genomics & CBM to cluster profiles with overlapping disease-relevant biomarkers & similar drug response predictions. CBM can identify pt populations who may benefit from certain therapeutic regimens, improving response rates, & give insights into the mechanisms by which each drug impacts the MDS-specific biomarkers

Citation Format: Leylah M. Drusbosky, Kimberly E. Hawkins, Amy Meacham, Elizabeth Wise, Neeraj Kumar Singh, Chandan Kumar, Sumanth M. Vasista, Rakhi P. Suseela, Taher Abbasi, Shireen Vali, Kaoru Tohyama, Maher Albitar, Peter P. Sayeski, Christopher R. Cogle. Genomics-driven clustering of disease-related biomarkers identifies therapeutic options in myelodysplastic syndromes (MDS) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4285.

Using social media to assess care coordination goals and plans for leukemia patients and survivors

Care coordination has been shown to have a positive effect on the management of chronic disease. Specific to the management of leukemia, coordination may occur between primary care physician, medical and radiation oncologists, surgeons, cardiologists, and genetics specialists. Experiencing gaps in communication and care coordination, many health consumers seek instrumental support in their social circles, including online forums and networks. The goal of this theory-guided study was to provide an in-depth assessment of how individuals use online forums to deliberate about their goals and plans for leukemia care coordination. Guided by the planning theory of communication, the data were collected from the American Cancer Society Cancer Survivors Network and included 125 original posts and 1,248 responses. Thematic analysis and axial coding were applied to analyze the data. Goal-related themes included overcoming the diffusion of care coordination and achieving health management cohesion. Planning themes included social health management, communication self-efficacy, and role deliberation. Online patient forums provide an interactive platform for patients and caregivers to engage in active conversations, which in turn can serve as identifiers of care coordination needs. Communication with those who share similar experiences allows cancer patients and survivors to accumulate functional health literacy, gain communication self-efficacy, and articulate a care coordination role acceptable to them.

Abstract CT085: iCare 1: A prospective clinical trial to predict treatment response based on mutanome-informed computational biology in patients with AML and MDS

Hypomethylating agents (HMAs) (azacitidine (aza), decitabine (dec)) and lenalidomide (len) are approved agents and used to treat patients with myelodysplastic syndromes (MDS) or acute myeloid leukemia (AML). Despite their widespread use, HMAs fail in the majority of these patients, and len fails in 75% of non-del(5q) MDS. Currently, no method exists to predict disease response, thus the management of MDS and AML patients is challenging.

Methods: Patients with AML or MDS were recruited to a clinical trial (NCT02435550) designed to assess predictive values by comparing computer predictions of drug response to actual clinical response. Genomic profiling was conducted by cytogenetics, whole exome sequencing, and array CGH. Genomic results were inputted into a computational software (Cellworks), which generates disease-specific protein network maps using PubMed and other resources. Digital drug simulations were conducted by quantitatively measuring drug effect on a cell growth score (proliferation + viability + apoptosis). Each patient-specific protein network was screened for the extent by which aza, dec or len reduced disease growth in a dose-respondent manner. Treatment was physician’s choice of SOC. Clinical outcomes were prospectively recorded. IWG criteria were used to define response. Western blot assays were performed to validate the predicted protein network perturbations. Fisher’s exact test was used to compare prediction values of the genomics-informed computer method versus empiric drug administration.

Results: 88 patients have had all molecular tests and computational modeling performed. Lab validation of computer-predicted, activated protein networks in 19 samples from 13 different patients showed correct prediction of 5 activated networks (Akt2, Akt3, PIK3CA, p38, Erk1/2) in 17 samples, with 89% accuracy. At the time of this report, 26/88 patients were eligible for efficacy evaluation. 8/26 patients showed clinical response to SOC therapy, 18/26 did not. 24/26 outcome predictions were correctly matched to their clinical outcomes, and 2/20 were incorrectly matched, resulting in 92% prediction accuracy, 80% PPV, 100% NPV, 100% sensitivity, and 89% specificity. The accuracy of the genomics-informed computer method was significantly greater than empiric drug administration (p=1.664e-05). New genomic signature rules were discovered to correlate with clinical response after aza, dec or len.

Summary: A computational method that models multiple genomic abnormalities simultaneously showed high predictive value of protein network aberrations and clinical outcomes after SOC treatments. The network method uncovered molecular reasons for drug failure and highlighted resistance pathways that could be targeted to recover chemosensitivity. This technology could also be used to establish eligibility criteria for precision enrollment in drug development trials

Citation Format: Leylah Drusbosky, Kimberly E. Hawkins, Shireen Vali, Taher Abbasi, Ansu Kumar, Neeraj Kumar Singh, Kabya Basu, Chandan Kumar, Amjad Husain, Caitlin Tucker, Randy A. Brown, Maxim Norkin, John Hiemenz, Jack Hsu, John Wingard, Christopher R. Cogle. iCare 1: A prospective clinical trial to predict treatment response based on mutanome-informed computational biology in patients with AML and MDS [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT085. doi:10.1158/1538-7445.AM2017-CT085

Targeting resolution of neuroinflammation after ischemic stroke with a lipoxin A4 analog: Protective mechanisms and long-term effects on neurological recovery

BACKGROUND

Resolution of inflammation is an emerging new strategy to reduce damage following ischemic stroke. Lipoxin A₄ (LXA ₄) is an anti-inflammatory, pro-resolution lipid mediator that reduces neuroinflammation in stroke. Since LXA ₄ is rapidly inactivated, potent analogs have been synthesized, including BML-111. We hypothesized that post-ischemic, intravenous treatment with BML-111 for 1 week would provide neuroprotection and reduce neurobehavioral deficits at 4 weeks after ischemic stroke in rats. Additionally, we investigated the potential protective mechanisms of BML-111 on the post-stroke molecular and cellular profile.

METHODS

A total of 133 male Sprague-Dawley rats were subjected to 90 min of transient middle cerebral artery occlusion (MCAO) and BML-111 administration was started at the time of reperfusion. Two methods of week-long BML-111 intravenous administration were tested: continuous infusion via ALZET ^® osmotic pumps (1.25 and 3.75 μg μl^-1 hr^-1), or freshly prepared daily single injections (0.3, 1, and 3 mg/kg). We report for the first time on the stability of BML-111 and characterized an optimal dose and a dosing schedule for the administration of BML-111.

RESULTS

One week of BML-111 intravenous injections did not reduce infarct size or improve behavioral deficits 4 weeks after ischemic stroke. However, post-ischemic treatment with BML-111 did elicit early protective effects as demonstrated by a significant reduction in infarct volume and improved sensorimotor function at 1 week after stroke. This protection was associated with reduced pro-inflammatory cytokine and chemokine levels, decreased M1 CD40+ macrophages, and increased alternatively activated, anti-inflammatory M2 microglia/macrophage cell populations in the post-ischemic brain.

CONCLUSION

These data suggest that targeting the endogenous LXA ₄ pathway could be a promising therapeutic strategy for the treatment of ischemic stroke. More work is necessary to determine whether a different dosing regimen or more stable LXA ₄ analogs could confer long-term protection.

Spatiotemporal Changes in P-glycoprotein Levels in Brain and Peripheral Tissues Following Ischemic Stroke in Rats

P-glycoprotein (P-gp) is known to transport a diverse array of xenobiotics, including therapeutic drugs. A member of the ATP-binding cassette (ABC) transporter family, P-gp is a protein encoded by the gene Mdr1 in humans and Abcb1 in rodents (represented by 2 isoforms Abcb1a and Abcb1b). Lining the luminal and abluminal membrane of brain capillary endothelial cells, P-gp is a promiscuous efflux pump extruding a variety of exogenous toxins and drugs. In this study, we measured dynamic changes in Abcb1a and Abcb1b transcripts and P-gp protein in the brain, liver, and kidney after experimental stroke. P-glycoprotein has been shown to increase in brain endothelial cells following hypoxia in vitro or after exposure to proinflammatory cytokines. Using a rat model of ischemic stroke, we hypothesized that P-gp expression will be increased in the brain, liver, and kidney in response to neuroinflammation following ischemic stroke. Adult Sprague Dawley rats underwent middle cerebral artery occlusion (MCAO) for 90 minutes and were killed at 4, 14, 24, and 48 hours postreperfusion onset to determine the time course of P-gp expression. To mimic ischemia occurring at the blood-brain barrier, rat brain endothelial (RBE4) cells were subjected to hypoxia and low glucose (HLG) for 16 hours. Immunoblotting analyses showed P-gp increases in brain and liver following 90-minute MCAO, as well as in cultured RBE4 cells after 16-hour HLG treatment, but fluctuated in the kidney depending on the time point. The relative roles of each isoform in the protein expression were analyzed with quantitative reverse transcriptase polymerase chain reaction. Ischemic stroke leads to significant increases in P-gp levels not only in the brain but also in the liver. The increase in P-gp could dramatically reduce the bioavailability and efficacy of neuroprotective drugs. Therefore, P-gp represents a big hurdle to drug delivery to the ischemic brain.

Adropin reduces paracellular permeability of rat brain endothelial cells exposed to ischemia-like conditions

Adropin is a peptide encoded by the energy homeostasis associated gene (Enho) and plays a critical role in the regulation of lipid metabolism, insulin sensitivity, and endothelial function. Little is known of the effects of adropin in the brain and whether this peptide modulates ischemia-induced blood-brain barrier (BBB) injury. Here, we used an in vitro BBB model of rat brain microvascular endothelial cells (RBE4) and hypothesized that adropin would reduce endothelial permeability during ischemic conditions. To mimic ischemic conditions in vitro, RBE4 cell monolayers were subjected to 16h hypoxia/low glucose (HLG). This resulted in a significant increase in paracellular permeability to FITC-labeled dextran (40kDa), a dramatic upregulation of vascular endothelial growth factor (VEGF), and the loss of junction proteins occludin and VE-cadherin. Notably, HLG also significantly decreased Enho expression and adropin levels. Treatment of RBE4 cells with synthetic adropin (1, 10 and 100ng/ml) concentration-dependently reduced endothelial permeability after HLG, but this was not mediated through protection to junction proteins or through reduced levels of VEGF. We found that HLG dramatically increased myosin light chain 2 (MLC2) phosphorylation in RBE4 cells, which was significantly reduced by adropin treatment. We also found that HLG significantly increased Rho-associated kinase (ROCK) activity, a critical upstream effector of MLC2 phosphorylation, and that adropin treatment attenuated that effect. These data indicate that treatment with adropin reduces endothelial cell permeability after HLG insult by inhibition of the ROCK-MLC2 signaling pathway. These promising findings suggest that adropin protects against endothelial barrier dysfunction during ischemic conditions.

The molecular neurobiology of the sleep-deprived, fuzzy brain

Sleep deprivation is well established to cause diminution of cognitive function, including disruption of both minute-to-minute working memory and decrements in the stabilization of long-term memories. Moreover, "replay" during sleep of episodes and sequences of events that were experienced during wakefulness has been implicated in consolidation of long-term memories. However, the molecular mechanisms underlying the role of sleep in memory function are just starting to be defined. In this issue of Science Signaling, Tudor et al identify one molecular component underlying the effects of sleep on memory function: dynamic experience-dependent regulation of protein synthesis in the hippocampus.

Abstract W MP85: Prostacyclin Receptor Activation With MRE-269 Reduces Infarct Size and Improves Long-term Neurological Recovery Following Ischemic Stroke in Both Young and Aged Rats

Activation of the prostacyclin (PGI2) IP receptor is protective in brain ischemia. However, there is very limited information of the molecular mechanisms of protection and the feasibility to target this pathway in stroke. MRE-269, a highly selective PGI2/IP receptor agonist, has been recently discovered. This IP agonist has a long half-life in vivo and is currently in phase III clinical trials for pulmonary hypertension. We hypothesized that post-ischemic treatment with MRE-269 provides neuroprotection in a rat ischemic stroke model. Young male rats (3-4-month old) were subjected to middle cerebral artery occlusion (MCAO) for 90 min and treated intravenously with either vehicle (n=14) or MRE-269 (0.1, 0.25, 0.5, and 1 mg/kg, n=10-14/group) at the start of reperfusion. At 48 h post-MCAO, rats were sacrificed to determine infarct size, blood-brain barrier (BBB) damage (IgG extravasation), hemorrhagic transformation (brain hemoglobin levels), and matrix metalloproteinase (MMP)-9 activity. In a separate experiment, aged male rats (18-20-month old) underwent 90 min of MCAO and randomly selected to receive intravenously either vehicle (n=11) or MRE-269 (0.25 mg/kg, n=11) starting at 4.5 h post-MCAO. Additional doses were given every 12 h for the first 48 h, and then one injection daily for 7 days post-MCAO. The accelerating rotarod and the adhesive removal tests were conducted before and at 3, 7, 14 and 21 days after MCAO by an investigator blinded to treatment groups. Infarct volume was quantified by MRI at 48 h and 21 days post-MCAO. In young rats, MRE-269 dose-dependently reduced cortical infarct size. MRE-269-treated rats (0.25 mg/kg) had significantly reduced BBB damage and less hemorrhagic transformation. Compared with the vehicle group, MRE-269-treated animals showed a significant reduction in brain MMP-9 activity. In aged rats, MRE-269 treatment resulted in a significant long-term recovery in both locomotor and somatosensory functions following MCAO. Quantitative MRI data showed that MRE-269 significantly reduced infarct volume compared with vehicle-treated rats. Our data suggest that targeting the PGI2/IP receptor with MRE-269 is a novel strategy to reduce neurovascular injury and promote long-term neurological recovery in ischemic stroke.

Neurovascular protection by post-ischemic intravenous injections of the lipoxin A4 receptor agonist, BML-111, in a rat model of ischemic stroke

Resolution of inflammation is an emerging new strategy to reduce damage following ischemic stroke. Lipoxin A4 (LXA4 ) is an anti-inflammatory, pro-resolution lipid mediator with high affinity binding to ALX, the lipoxin A4 receptor. Since LXA4 is rapidly inactivated, potent analogs have been created, including the ALX agonist BML-111. We hypothesized that post-ischemic intravenous administration of BML-111 would provide protection to the neurovascular unit and reduce neuroinflammation in a rat stroke model. Animals were subjected to 90 min of middle cerebral artery occlusion (MCAO) and BML-111 was injected 100 min and 24 h after stroke onset and animals euthanized at 48 h. Post-ischemic treatment with BML-111 significantly reduced infarct size, decreased vasogenic edema, protected against blood-brain barrier disruption, and reduced hemorrhagic transformation. Matrix metalloproteinase-9 and matrix metalloproteinase-3 were significantly reduced following BML-111 treatment. Administration of BML-111 dramatically decreased microglial activation, as seen with CD68, and neutrophil infiltration and recruitment, as assessed by levels of myeloperoxidase and intracellular adhesion molecule-1. The tight junction protein zona occludens-1 was protected from degradation following treatment with BML-111. These results indicate that post-ischemic activation of ALX has pro-resolution effects that limit the inflammatory damage in the cerebral cortex and helps maintain blood-brain barrier integrity after ischemic stroke.

Fluorometric immunocapture assay for the specific measurement of matrix metalloproteinase-9 activity in biological samples: application to brain and plasma from rats with ischemic stroke

BACKGROUND

Matrix metalloproteinases are important factors in the molecular mechanisms leading to neuronal injury in many neurological disorders. Matrix metalloproteinase (MMP)-9 is up-regulated after cerebral ischemia and neuroinflammation and is actively involved in blood-brain barrier disruption. Current methods of measuring MMP-9 activity, such as gelatin-substrate zymography, are unspecific and arduous. Here we developed an immunocapture assay with high efficiency, specificity, and sensitivity for quantifying endogenously active as well as total MMP-9 activity.

RESULTS

A fluorescence resonance energy transfer (FRET) peptide-based immunocapture assay was developed that enables the accurate assessment of total and active forms of MMP-9 in complex biological samples. The FRET assay demonstrated correct and efficient binding of MMP-9 to a mouse monoclonal MMP-9 antibody and high specificity of the immunocapture antibody for MMP-9. Total and active levels of MMP-9 were measured in rat brain homogenates, plasma, human HT-1080 conditioned media, and RBE4 endothelial cell lysates. The FRET immunocapture assay yielded highly similar results for total MMP-9 activity when compared to gelatin-substrate zymography.

CONCLUSIONS

We suggest that the new FRET peptide-based immunocapture assay is a viable replacement of zymography for sensitive and high throughput quantification of MMP-9 activity in biological samples.