Enhanced cerebral ischemic lesions after two-vein occlusion in diabetic rats

Diabetic Rodent Models for Chronic Stroke Studies

Chronic diabetes may cause secondary complications like stroke and also increase post-stroke brain damage. In stroke research, the Stroke Therapy Academic Industry Roundtable (STAIR) identified criteria to increase translational value of preclinical studies, which highlighted the importance of using animal models of comorbidities. Numerous animal models have been used to study the aggravation of ischemic brain damage in diabetics. In this chapter, we discuss rat and mouse models of streptozotocin (STZ)-induced diabetes, with an efficient method provided. We also provide an overview of spontaneously diabetic rodent models. We present different pathophysiological features of diabetes in each rodent model along with the advantages and disadvantages of each model. Utilizing these models may aid the advancement of novel treatments and therapies to lower ischemic brain damage in patients of diabetes.

Early BBB breakdown and subacute inflammasome activation and pyroptosis as a result of cerebral venous thrombosis

Cerebral venous thrombosis (CVT) is a rare form of cerebral stroke that causes a variety of symptoms, ranging from mild headache to severe morbidity or death in the more severe forms. The use of anti-coagulant or thrombolytic agents is the classical treatment for CVT. However, the development of new therapies for the treatment of the condition has not been the focus. In this study, we aimed to analyze the pathophysiology of CVT and to identify the pathways associated with its pathology. Moreover, mechanisms that are potential drug targets were identified. Our data showed the intense activation of immune cells, particularly the microglia, along with the increase in macrophage activity and NLRP3 inflammasome activation that is indicated by NLRP3, IL-1β, and IL-18 gene and caspase-1 upregulation and cleavage as well as pyroptotic cell death. Leukocytes were observed in the brain parenchyma, indicating a role in CVT-induced inflammation. In addition, astrocytes were activated, and they induced glial scar leading to parenchymal contraction during the subacute stage and tissue loss. MMP9 was responsible primarily for the BBB breakdown after CVT and it is mainly produced by pericytes. MMP9 activation was observed before inflammatory changes, indicating that BBB breakdown is the initial driver of the pathology of CVT. These results show an inflammation driven pathophysiology of CVT that follows MMP9-mediated BBB breakdown, and identified several targets that can be targeted by pharmaceutical agents to improve the neuroinflammation that follows CVT, such as MMP9, NLRP3, and IL-1β. Some of these pharmaceutical agents are already in clinical practice or under clinical trials indicating a good potential for translating this work into patient care.

Coenzyme Q10 ameliorates cerebral ischemia reperfusion injury in hyperglycemic rats

The purpose of this study is to investigate the effect of coenzyme Q10 (CoQ10) on focal cerebral ischemia/reperfusion (I/R) injury in hyperglycemic rats and the possible involved mechanisms. In this study, we established the transient middle cerebral artery occlusion (MCAO) for 30min in the rats with diabetic hyperglycemia. The neurological deficit score, 2,3,5-triphenyltetrazolium chloride (TTC) staining and pathohistology are applied to detect the extent of the damage. The expression of Fis1, Mfn2 and Lc3 in the brain is investigated by immunohistochemical and Western blotting techniques. The results showed that the streptozotocin-induced diabetic hyperglycemia and MCAO-induced focal cerebral ischemia were successfully prepared in rats. In the hyperglycemic group, the neurological deficit scores, infarct volumes, and number of pyknotic cells were higher than that in the normalglycemic group at 24h and/or 72h reperfusion. Pretreated with CoQ10 (10mg/kg) for four weeks could significantly reduce the neurological scores, infarct volume, and pyknotic cells at 24h and/or 72h reperfusion of the hyperglycemic rats compared with non-CoQ10 pretreated hyperglycemic animals. Immunohistochemistry and Western blotting showed that pretreatment with CoQ10 or insulin could significantly reduce the expression of Fis1 protein in the brain at 24h and 72h reperfusion. Inversely, a significantly increased expression of Mfn2 was observed in the rats CoQ10 or insulin pretreated at 24h and/or 72h reperfusion when compared with matched hyperglycemic rats. These results demonstrated that hyperglycemia could aggravate ischemic brain injury. Pretreatment with CoQ10 might ameliorate the diabetic hyperglycemia aggravated I/R brain damage in the MCAO rats by maintain the balance between mitochondrial fission and fusion.

Diabetic aggravation of stroke and animal models

Cerebral ischemia in diabetics results in severe brain damage. Different animal models of cerebral ischemia have been used to study the aggravation of ischemic brain damage in the diabetic condition. Since different disease conditions such as diabetes differently affect outcome following cerebral ischemia, the Stroke Therapy Academic Industry Roundtable (STAIR) guidelines recommends use of diseased animals for evaluating neuroprotective therapies targeted to reduce cerebral ischemic damage. The goal of this review is to discuss the technicalities and pros/cons of various animal models of cerebral ischemia currently being employed to study diabetes-related ischemic brain damage. The rational use of such animal systems in studying the disease condition may better help evaluate novel therapeutic approaches for diabetes related exacerbation of ischemic brain damage.

Carotid artery stenosis is exacerbated in spontaneously obese model rats with diabetes

AIM

Population studies have shown obesity and diabetes to be risk factors for atherosclerosis. We assessed changes in the common carotid arteries in rat models of obesity and diabetes without hypertension.

METHODS

Twenty 30-week-old male spontaneously diabetic and obese model Otsuka Long-Evans Tokushima Fatty (OLETF) and 20 control Long-Evans Tokushima Otsuka (LETO) rats were used in the experiments. The animals were considered diabetic if the plasma glucose level peaked at >300 mg/dL and remained at >200 mg/dL for 120 minutes. Blood gas physiological parameters were continuously monitored under anesthesia, and the flow of the carotid artery was assessed with ultrasonography. All animals were sacrificed with an overdose of anesthesia at the end of the experiment. Sections of the middle portion of the internal carotid artery were cut and stained with hematoxylin and eosin to assess the overall morphology.

RESULTS

All OLETF rats were diabetic, and all LETO rats were non-diabetic. The physiological parameters did not differ significantly between the control and model rats, whereas the carotid artery wall thickness (19.3 ± 3.2 vs. 6.1 ± 4.5 μm) was significantly different between the two groups. The blood flow velocity in the common carotid artery determined using ultrasonography and color Doppler sonography was significantly increased during systole in the model rats compared with that observed in the control rats (203 ± 20.3 vs. 55.3 ± 21.4 cm/sec).

CONCLUSIONS

The OLETF rats were obese, and diabetes worsened the degree of carotid artery stenosis. These results indicate the possibility of new therapies for carotid artery stenosis in obese and diabetic patients.

Cilostazol minimizes venous ischemic injury in diabetic and normal rats

We evaluated the effects of cilostazol on venous infarction produced by a photothrombotic two-vein occlusion (2VO) model in diabetic and control rats. The cerebral blood flow (CBF) between the occluded veins was measured by laser Doppler flowmetry for 4 hours after 2VO. Infarct size and immunohistochemistry were evaluated 24, 48, 96, and 168 hours after 2VO. Cilostazol was administered 1 hour after 2VO, and thereafter at a continuous oral dose of 60 mg/kg per day. Cilostazol reduced the infarct size, and the number of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL)-positive apoptotic and B-cell lymphoma 2-associated X protein (Bax)-positive cells, and improved the CBF in control rats. In diabetic rats, cilostazol reduced the infarct size, and the number of TUNEL-positive apoptotic and Bax-positive cells, 96 and 168 hours after 2VO, but did not improve the CBF 4 hours after 2VO. Cilostazol increased the number of B-cell lymphoma 2 (Bcl-2)-positive cells in both strains 48, 96, and 168 hours after 2VO, but did not improve vessel wall thickness or collagen deposits. Cilostazol appeared to limit venous infarcts by improving the penumbral CBF in nondiabetic rats, and inhibited pro-apoptotic changes through Bcl-2 overexpression, without improving the CBF in diabetic rats.