Evaluating the comorbidities of age and cigarette smoking on stroke outcomes in the context of anti-complement mitigation strategies

Abstract

Multiple neuroprotective agents have shown beneficial effects in rodent models of stroke, but they have failed to translate in the clinic. In this perspective, we consider that a likely explanation for this failure, at least in part, is that there has been inadequate assessment of functional outcomes in preclinical stroke models, as well the use of young healthy animals that are not representative of clinical cohorts. Although the impact of older age and cigarette smoking comorbidities on stroke outcomes is well documented clinically, the impact of these (and other) stroke comorbidities on the neuroinflammatory response after stroke, as well as the response to neuroprotective agents, remains largely unexplored. We have shown that a complement inhibitor (B4Crry), that targets specifically to the ischemic penumbra and inhibits complement activation, reduces neuroinflammation and improves outcomes following murine ischemic stroke. For this perspective, we discuss the impact of age and smoking comorbidities on outcomes after stroke, and we experimentally assess whether increased complement activation contributes to worsened acute outcomes with these comorbidities. We found that the pro-inflammatory effects of aging and smoking contribute to worse stroke outcomes, and these effects are mitigated by complement inhibition.

Keywords: age; cigarette smoke; comorbidity; complement; stroke.

Figure 1

Effect of B4-Crry treatment on neurological deficit, mortality and lesion volume 24 hours after MCAO in aged and CS exposed mice. (A) Aged + CS exposed mice. (B) Aged non-CS exposed mice. (C) Young + CS exposed mice. Neurological deficit scores, Mann Whitney test. Mortality, Chi squared test. Lesion Volume, T-test. For all groups, n=7-11. Error bars = SEM.* indicate P value less than 5.

Figure 2

Extent of Microgliosis and loss of dendritic arborization at 24 hours after MCAO in the perilesional area of B4-Crry and vehicle treated CS exposed and non-CS exposed aged mice. (A, B) Immunofluorescence staining for MAP2 (dendritic marker, green), microglia (Iba1, red), and neurons (NeuN, cyan) demonstrating wider extent of microgliosis and dendritic loss in vehicle treated compared to B4Crry treated mice. Representative images. (C) Quantification of images in (B) showing percentage area of microgliosis in the ipsilateral hemisphere. Student’s T-test. *p<0.05. **p<0.01. Mean +/- SEM. (D) Quantification of images in (B) showing percentage area with loss of MAP2 signal indicating loss of dendritic arborization in the ipsilateral hemisphere in aged mice (left) and aged + CS exposed mice (right), comparing vehicle to B4Crry treatment. Student’s t-test. *p<0.05. Mean +/- SEM.