Tumour Necrosis Factor-α Inhibition Improves Stroke Outcome in a Mouse Model of Rheumatoid Arthritis

Abstract

Rheumatoid Arthritis (RA) is a chronic inflammatory disorder where incidence and severity of myocardial infarction are increased. Data on the incidence and outcome of stroke are conflicting. Thus, we investigated outcome after Ischemia/Reperfusion (I/R) brain injury in a mouse model of RA and assessed for the role of the tumour necrosis factor-α (TNF-α) inhibitor Infliximab herein. We used a TNF-α reliant mouse model of RA. RA and wildtype (WT) animals were treated with vehicle (RA/WT) or Infliximab (RA Infliximab) for 4 weeks, before undergoing I/R brain injury. RA-animals displayed larger strokes and poorer neurological performance. Immunohistochemistry on brain sections revealed increased numbers of resident and peripheral innate immune cells (microglia and macrophages); increased Blood-Brain-Barrier (BBB)-disruption; decreased levels of the tight junction proteins (TJPs) claudin-5 and occludin; increased expression of matrix-metalloproteinases (MMP)-3 and -9 and enhanced lipid peroxidation. Treatment with Infliximab corrected these alterations. We show that RA associates to worse stroke-outcome via exacerbated BBB degradation by decrease of the TJPs claudin-5 and occludin. We identified MMPs-3 and -9 and increased oxidative stress as potential mediators thereof. Increased numbers of resident and peripheral innate immune cells (microglia and macrophages) may in turn contribute to all these effects. Infliximab-treatment restored the phenotype of RA-mice to baseline. Our data provide evidence clearly linking RA to adverse stroke-outcome in mice and indicate an approved TNF-α inhibitor as a potential strategy to reduce stroke-burden in this setting.

Regulation of blood–brain barrier integrity by microglia in health and disease: A therapeutic opportunity

“…47 The ability of TNF-a to disrupt tight junctions and open a paracellular route between apposing endothelial cells at the BBB is related to the upregulation of matrix metalloproteinase (MMP) -2, -3 and -9 enzymes in the extracellular matrix. 48,49 Similar modifications to BBB functional integrity have been reported following exposure to IL-1b, 50 IL-6, 51 and IL-12. 51 Proinflammatory cytokines can also modulate expression of critical BBB transporters as shown in in vitro and ex vivo studies where brain microvascular endothelial cells or isolated brain microvessels were directly exposed to proinflammatory cytokines.…”

Cytokines as therapeutic targets for cardio- and cerebrovascular diseases

“…Increasing TNF-α levels in the stroke and penumbra areas facilitate the recruitment of circulating inflammatory cells that, once reached the injury site, get activated and in turn release TNF-α, thus promoting a vicious circle involving different pro-inflammatory cytokines [ 50 ]. Of interest, TNF-α contributes to the dysfunctional activation of endothelial cells in the blood–brain barrier (BBB), increasing their production of cytokines, ROS, and adhesion molecules, while reducing their barrier function which is a known determinant of stroke outcome [ 26 , 41 ]. Indeed, TNF-α also up-regulates the expression of different metalloproteinases, including MMP-9 and MMP-3 that are known to digest the BBB regulating tight and adherens junctions such as occludin, claudin-5, and vascular endothelium (VE)-cadherin [ 26 ].…”

“…Of interest, TNF-α contributes to the dysfunctional activation of endothelial cells in the blood–brain barrier (BBB), increasing their production of cytokines, ROS, and adhesion molecules, while reducing their barrier function which is a known determinant of stroke outcome [ 26 , 41 ]. Indeed, TNF-α also up-regulates the expression of different metalloproteinases, including MMP-9 and MMP-3 that are known to digest the BBB regulating tight and adherens junctions such as occludin, claudin-5, and vascular endothelium (VE)-cadherin [ 26 ]. Of interest TNF-α, as well as many other inflammatory mediators including MMP-9, has shown also neurotoxic effects, thereby potentially increasing direct neuronal damage [ 82 , 202 ].…”

Neurodegenerative disease treatments by direct TNF reduction, SB623 cells, maraviroc and irisin and MCC950, from an inflammatory perspective – a Commentary

“…Nowadays much literature points to the harmfulness of excess TNF in the central nervous system through a combination of loss of homeostasis, and therefore potentially reversible function loss, as well as cell death. Initially this was through outcomes of administering etanercept, a specific anti-TNF biological to AD patients in a 2006 uncontrolled trial [18], and since then in AD model mice [46], stroke model mice [47][48][49], further AD patients [50][51][52][53][54], poststroke patients [55,56], mouse PD models [20,57], TBI patients [56], and a rat TBI model [58]. The routes of administration varied in ways described by these authors and do not affect the general human open trials, and inadvertent effects of anti-TNF agents chronically administered for approved treatments, are consistent with this.…”

“…This remarkable document [22] can perhaps be best characterized as being as fulsome in praise of excess TNF being a central mechanism for stroke and TBI as is possible without actually mentioning TNF, or the links their work has with this cytokine. For example, these human CCR5-Δ32 carriers would have been predicted, from experience since 2011 of anti-TNF improving stroke outcomes [47][48][49]55,56], to recover better from this condition by virtue of their documented innate poor capacity to generate TNF [80]. Maraviroc, an effective anti-TNF agent [81][82][83][84] is shown by these authors [22] to provide useful outcomes in post-stroke and post-TBI mice.…”