Biology subjects

Howell, J. A.

Publications and source records attributed to Howell, J. A..

3 recordsLinked to original sources

bioRxiv2025

Effects of Global Ripk2 Genetic Deficiency in Aged Mice following Experimental Ischemic Stroke

Besides the loss of blood and oxygen reaching the ischemic tissue, many secondary effects of ischemic stroke can cause additional tissue death, including inflammation, oxidative stress, and proteomic disturbances. Receptor-interacting serine/threonine kinase 2 (RIPK2) is an important mediator in the post-stroke inflammatory cascade that responds to signals and molecular patterns released by dead or dying cells in the ischemic area. We hypothesize that RIPK2 signaling worsens injury and neurological recovery post-stroke and that global deletion of Ripk2 will be protective following ischemic stroke in aged mice. Aged (18-24 months) male mice were subjected to permanent middle cerebral artery occlusion (pMCAO). Vertical grid, weight grip, and open field were conducted at baseline and on days 1, 2, 3, 8, 15, and 22 post-stroke. Cognitive tests (novel object recognition and Y-maze) were performed at baseline and day 28 post-stroke. Infarct size was measured using cresyl violet staining, and reactive gliosis was measured using Iba1 and GFAP staining at day 28 post-stroke. Global deletion of Ripk2 (Ripk2-/-) in aged mice resulted in smaller infarct volume and improved performance on vertical grid and weight grip tests compared to aged wildtype (WT) mice. Additionally, aged Ripk2-/- mice had less Iba1 staining in the ipsilateral cortex than the aged WT control mice. This study further elucidates the role of RIPK2 signaling in the ischemic cascade and expands our knowledge of RIPK2 in stroke to aged mice. These results support the hypothesis that RIPK2 signaling worsens injury post-stroke and may be an attractive candidate for therapeutic intervention.

neuroscience↗

bioRxiv2024

RIPK2 is crucial for the microglial inflammatory response to bacterial muramyl dipeptide but not to lipopolysaccharide

Receptor-interacting serine/threonine protein kinase 2 (RIPK2) is a kinase that plays an essential role in the modulation of innate and adaptive immune responses. As a downstream signaling molecule for nucleotide-binding oligomerization domain 1 (NOD1), NOD2, and Toll-like receptors (TLRs), it is implicated in the signaling triggered by recognition of microbe-associated molecular patterns by NOD1/2 and TLRs. Upon activation of these innate immune receptors, RIPK2 mediates the release of pro-inflammatory factors by activating mitogen-activated protein kinases (MAPKs) and nuclear factor-kappa B (NF-{kappa}B). However, whether RIPK2 is essential for downstream inflammatory signaling following the activation of NOD1/2, TLRs, or both remains controversial. In this study, we examined the role of RIPK2 in NOD2- and TLR4-dependent signaling cascades following stimulation of microglial cells with bacterial muramyl dipeptide (MDP), a NOD2 agonist, or lipopolysaccharide (LPS), a TLR4 agonist. We utilized a highly specific proteolysis targeting chimera (PROTAC) molecule, GSK3728857A, and found dramatic degradation of RIPK2 in a concentration- and time-dependent manner. Importantly, the PROTAC completely abolished MDP-induced increases in iNOS and COX-2 protein levels and pro-inflammatory gene transcription of Nos2, Ptgs2, Il-1{beta}, Tnf, Il6, Ccl2, and Mmp9. However, increases in iNOS and COX-2 proteins and pro-inflammatory gene transcription induced by the TLR4 agonist, LPS, were only slightly attenuated with the GSK3728857A pretreatment. Further findings revealed that the RIPK2 PROTAC completely blocked the phosphorylation and activation of p65 NF-{kappa}B and p38 MAPK induced by MDP, but it had no effects on the phosphorylation of these two mediators triggered by LPS. Collectively, our findings strongly suggest that RIPK2 plays an essential role in the inflammatory responses of microglia to bacterial MDP but not to LPS.

neuroscience↗

bioRxiv2023

Elastin-like polypeptide delivery of anti-inflammatory peptides to the brain following ischemic stroke

Inflammatory processes are activated following ischemic strokes and lead to increased tissue damage for weeks following the ischemic insult, but there are no approved therapies that target this inflammation-induced secondary injury. Here, we report that SynB1-ELP-p50i, a novel protein inhibitor of the nuclear factor kappa B (NF-{kappa}B) inflammatory cascade bound to drug carrier elastin-like polypeptide (ELP), is able to enter both neurons and microglia, cross the blood-brain barrier, localize exclusively in the ischemic core and penumbra in Wistar-Kyoto and spontaneously hypertensive rats (SHRs), and reduce infarct volume in male SHRs. Additionally, in male SHRs, SynB1-ELP-p50i treatment improves survival for 14 days following stroke with no effects of toxicity or peripheral organ dysfunction. These results show high potential for ELP-delivered biologics for therapy of ischemic stroke and other central nervous system disorders and further support targeting inflammation in ischemic stroke.

neuroscience↗