Prasad Chunduri

Intravenous immunoglobulin suppresses NLRP1 and NLRP3 inflammasome-mediated neuronal death in ischemic stroke

Multi-protein complexes called inflammasomes have recently been identified and shown to contribute to cell death in tissue injury. Intravenous immunoglobulin (IVIg) is an FDA-approved therapeutic modality used for various inflammatory diseases. The objective of this study is to investigate dynamic responses of the NLRP1 and NLRP3 inflammasomes in stroke and to determine whether the NLRP1 and NLRP3 inflammasomes can be targeted with IVIg for therapeutic intervention. Primary cortical neurons were subjected to glucose deprivation (GD), oxygen–glucose deprivation (OGD) or simulated ischemia-reperfusion (I/R). Ischemic stroke was induced in C57BL/6J mice by middle cerebral artery occlusion, followed by reperfusion. Neurological assessment was performed, brain tissue damage was quantified, and NLRP1 and NLRP3 inflammasome protein levels were evaluated. NLRP1 and NLRP3 inflammasome components were also analyzed in postmortem brain tissue samples from stroke patients. Ischemia-like conditions increased the levels of NLRP1 and NLRP3 inflammasome proteins, and IL-1β and IL-18, in primary cortical neurons. Similarly, levels of NLRP1 and NLRP3 inflammasome proteins, IL-1β and IL-18 were elevated in ipsilateral brain tissues of cerebral I/R mice and stroke patients. Caspase-1 inhibitor treatment protected cultured cortical neurons and brain cells in vivo in experimental stroke models. IVIg treatment protected neurons in experimental stroke models by a mechanism involving suppression of NLRP1 and NLRP3 inflammasome activity. Our findings provide evidence that the NLRP1 and NLRP3 inflammasomes have a major role in neuronal cell death and behavioral deficits in stroke. We also identified NLRP1 and NLRP3 inflammasome inhibition as a novel mechanism by which IVIg can protect brain cells against ischemic damage, suggesting a potential clinical benefit of therapeutic interventions that target inflammasome assembly and activity.

Pathogenesis of acute stroke and the role of inflammasomes

Inflammation is an innate immune response to infection or tissue damage that is designed to limit harm to the host, but contributes significantly to ischemic brain injury following stroke. The inflammatory response is initiated by the detection of acute damage via extracellular and intracellular pattern recognition receptors, which respond to conserved microbial structures, termed pathogen-associated molecular patterns or host-derived danger signals termed damage-associated molecular patterns. Multi-protein complexes known as inflammasomes (e.g. containing NLRP1, NLRP2, NLRP3, NLRP6, NLRP7, NLRP12, NLRC4, AIM2 and/or Pyrin), then process these signals to trigger an effector response. Briefly, signaling through NLRP1 and NLRP3 inflammasomes produces cleaved caspase-1, which cleaves both pro-IL-1β and pro-IL-18 into their biologically active mature pro-inflammatory cytokines that are released into the extracellular environment. This review will describe the molecular structure, cellular signaling pathways and current evidence for inflammasome activation following cerebral ischemia, and the potential for future treatments for stroke that may involve targeting inflammasome formation or its products in the ischemic brain.

Intermittent fasting attenuates inflammasome activity in ischemic stroke

Recent findings have revealed a novel inflammatory mechanism that contributes to tissue injury in cerebral ischemia mediated by multi-protein complexes termed inflammasomes. Intermittent fasting (IF) can decrease the levels of pro-inflammatory cytokines in the periphery and brain. Here we investigated the impact of IF (16h of food deprivation daily) for 4months on NLRP1 and NLRP3 inflammasome activities following cerebral ischemia. Ischemic stroke was induced in C57BL/6J mice by middle cerebral artery occlusion, followed by reperfusion (I/R). IF decreased the activation of NF-κB and MAPK signaling pathways, the expression of NLRP1 and NLRP3 inflammasome proteins, and both IL-1β and IL-18 in the ischemic brain tissue. These findings demonstrate that IF can attenuate the inflammatory response and tissue damage following ischemic stroke by a mechanism involving suppression of NLRP1 and NLRP3 inflammasome activity.

Cardiovascular changes during maturation and ageing in male and female spontaneously hypertensive rats

Background: Cardiovascular remodeling leading to heart failure is common in the elderly. Testing effective pharmacological treatment of human heart failure requires a suitable animal model that adequately mimics the human disease state. Methods: This study has characterized the structural, functional, and electrical characteristics of the cardiovascular system throughout the lifespan in male and female spontaneously hypertensive rats (SHRs), a genetic model of chronic hypertension-induced cardiovascular remodeling, and age- and gender-matched normotensive controls, to determine whether ageing SHRs mimic the changes seen in ageing humans. Results: Both the ageing male and female SHRs developed progressive hypertension, ventricular hypertrophy, left ventricular fibrosis, action potential prolongation without impaired glucose tolerance. Male SHRs from 15 months of age exhibited left ventricular wall thinning and chamber dilation, together with systolic and diastolic dysfunction and increased cardiac stiffness and increased erythrocyte superoxide production, which were not present in the female SHRs. Conclusion: Ageing male SHRs in contrast to the female SHRs, better mimic the chronic heart failure in humans produced by chronic hypertension. Ageing male SHRs could then be used to investigate proposed therapeutic interventions for chronic congestive heart failure in humans.

Evidence That the EphA2 Receptor Exacerbates Ischemic Brain Injury

Ephrin (Eph) signaling within the central nervous system is known to modulate axon guidance, synaptic plasticity, and to promote long-term potentiation. We investigated the potential involvement of EphA2 receptors in ischemic stroke-induced brain inflammation in a mouse model of focal stroke. Cerebral ischemia was induced in male C57Bl6/J wild-type (WT) and EphA2-deficient (EphA2−/−) mice by middle cerebral artery occlusion (MCAO; 60 min), followed by reperfusion (24 or 72 h). Brain infarction was measured using triphenyltetrazolium chloride staining. Neurological deficit scores and brain infarct volumes were significantly less in EphA2−/− mice compared with WT controls. This protection by EphA2 deletion was associated with a comparative decrease in brain edema, blood-brain barrier damage, MMP-9 expression and leukocyte infiltration, and higher expression levels of the tight junction protein, zona occludens-1. Moreover, EphA2−/− brains had significantly lower levels of the pro-apoptotic proteins, cleaved caspase-3 and BAX, and higher levels of the anti-apoptotic protein, Bcl-2 as compared to WT group. We confirmed that isolated WT cortical neurons express the EphA2 receptor and its ligands (ephrin-A1–A3). Furthermore, expression of all four proteins was increased in WT primary cortical neurons following 24 h of glucose deprivation, and in the brains of WT mice following stroke. Glucose deprivation induced less cell death in primary neurons from EphA2−/− compared with WT mice. In conclusion, our data provide the first evidence that the EphA2 receptor directly contributes to blood-brain barrier damage and neuronal death following ischemic stroke.

Evidence that NF-κB and MAPK Signaling Promotes NLRP Inflammasome Activation in Neurons Following Ischemic Stroke

Multi-protein complexes, termed “inflammasomes,” are known to contribute to neuronal cell death and brain injury following ischemic stroke. Ischemic stroke increases the expression and activation of nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) Pyrin domain containing 1 and 3 (NLRP1 and NLRP3) inflammasome proteins and both interleukin (IL)-1β and IL-18 in neurons. In this study, we provide evidence that activation of either the NF-κB and MAPK signaling pathways was partly responsible for inducing the expression and activation of NLRP1 and NLRP3 inflammasome proteins and that these effects can be attenuated using pharmacological inhibitors of these two pathways in neurons and brain tissue under in vitro and in vivo ischemic conditions, respectively. Moreover, these findings provided supporting evidence that treatment with intravenous immunoglobulin (IVIg) preparation can reduce activation of the NF-κB and MAPK signaling pathways resulting in decreased expression and activation of NLRP1 and NLRP3 inflammasomes, as well as increasing expression of anti-apoptotic proteins, Bcl-2 and Bcl-xL, in primary cortical neurons and/or cerebral tissue under in vitro and in vivo ischemic conditions. In summary, these results provide compelling evidence that both the NF-κB and MAPK signaling pathways play a pivotal role in regulating the expression and activation of NLRP1 and NLRP3 inflammasomes in primary cortical neurons and brain tissue under ischemic conditions. In addition, treatment with IVIg preparation decreased the activation of the NF-κB and MAPK signaling pathways, and thus attenuated the expression and activation of NLRP1 and NLRP3 inflammasomes in primary cortical neurons under ischemic conditions. Hence, these findings suggest that therapeutic interventions that target inflammasome activation in neurons may provide new opportunities in the future treatment of ischemic stroke.

l-Carnitine Attenuates Cardiac Remodelling rather than Vascular Remodelling in Deoxycorticosterone Acetate-Salt Hypertensive Rats

L-carnitine is an important co-factor in fatty acid metabolism by mitochondria. This study has determined whether oral administration of L-carnitine prevents remodelling and the development of impaired cardiovascular function in deoxycorticosterone acetate (DOCA)-salt hypertensive rats (n = 6-12; #p < 0.05 versus DOCA-salt). Uninephrectomized rats administered DOCA (25 mg every 4th day s.c.) and 1% NaCl in drinking water for 28 days developed cardiovascular remodelling shown as systolic hypertension, left ventricular hypertrophy, increased thoracic aortic and left ventricular wall thickness, increased left ventricular inflammatory cell infiltration together with increased interstitial collagen and increased passive diastolic stiffness and vascular dysfunction with increased plasma malondialdehyde concentrations. Treatment with L-carnitine (1.2% in food; 0.9 mg/g/day in DOCA-salt rats) decreased blood pressure (DOCA-salt 169 +/- 2; + L-carnitine 148 +/- 6# mmHg), decreased left ventricular wet weights (DOCA-salt 3.02 +/- 0.07; + L-carnitine 2.72 +/- 0.06# mg/g body-wt), decreased inflammatory cells in the replacement fibrotic areas, reduced left ventricular interstitial collagen content (DOCA-salt 14.4 +/- 0.2; + L-carnitine 8.7 +/- 0.5# % area), reduced diastolic stiffness constant (DOCA-salt 26.9 +/- 0.5; + L-carnitine 23.8 +/- 0.5# dimensionless) and decreased plasma malondialdehyde concentrations (DOCA-salt 26.9 +/- 0.8; + L-carnitine 21.2 +/- 0.4# micromol/l) without preventing endothelial dysfunction. L-carnitine attenuated the cardiac remodelling and improved cardiac function in DOCA-salt hypertension but produced minimal changes in aortic wall thickness and vascular function. This study suggests that the mitochondrial respiratory chain is a significant source of reactive oxygen species in the heart but less so in the vasculature in DOCA-salt rats, underlying the relatively selective cardiac responses to L-carnitine treatment.

Changes in Biology Self-Efficacy during a First-Year University Course.

Biology self-efficacy was measured in first-year students. Self-efficacy was lower in females than in males, most noticeably in high-achieving students. High school experience contributed to self-efficacy at the beginning of the semester, and this was replaced by progressive grades at the end of the semester. Self-efficacy did not correlate with exam grades.

Are they using my feedback? The extent of students’ feedback use has a large impact on subsequent academic performance

Feedback is known to have a large influence on student learning gains, and the emergence of online tools has greatly enhanced the opportunity for delivering timely, expressive, digital feedback and for investigating its learning impacts. However, to date there have been no large quantitative investigations of the feedback provided by large teams of markers, feedback use by large cohorts of students, nor its impact on students’ academic performance across successive assessment tasks. We have developed an innovative online system to collect large-scale data on digital feedback provision and use. Our markers (n = 38) used both audio and typed feedback modalities extensively, providing 388 ± 4 and 1126 ± 37 words per report for first- and second-year students, respectively. Furthermore, 92% of first year and 85% of second-year students accessed their feedback, with 58% accessing their feedback for over an hour. Lastly, the amount of time students spent interacting with feedback is significantly related to the rate of improvement in subsequent assessment tasks. This study challenges assertions that many students do not collect, or use, their feedback. More importantly, we offer novel insights into the relationships between feedback provision, feedback use and successful academic outcomes.

The role of neuropeptides in adverse myocardial remodeling and heart failure

In addition to traditional neurotransmitters of the sympathetic and parasympathetic nervous systems, the heart also contains numerous neuropeptides. These neuropeptides not only modulate the effects of neurotransmitters, but also have independent effects on cardiac function. While in most cases the physiological actions of these neuropeptides are well defined, their contributions to cardiac pathology are less appreciated. Some neuropeptides are cardioprotective, some promote adverse cardiac remodeling and heart failure, and in the case of others their functions are unclear. Some have both cardioprotective and adverse effects depending on the specific cardiac pathology and progression of that pathology. In this review, we briefly describe the actions of several neuropeptides on normal cardiac physiology, before describing in more detail their role in adverse cardiac remodeling and heart failure. It is our goal to bring more focus toward understanding the contribution of neuropeptides to the pathogenesis of heart failure, and to consider them as potential therapeutic targets.