Impaired Wound Healing after Cerebral Hypoxia—Ischemia in the Diabetic Mouse

Abstract

Impaired peripheral wound healing is a hallmark of diabetis pathology and has been attributed to compromised macrophage activation. Stroke is another component of diabetic pathology, with increased tissue infarction and worsened recovery although the mechanisms remain unresolved. In this study, we investigated whether a compromised glial/macrophage response might contribute to cerebral hypoxic-ischemic (H/I) brain damage in diabetic (db/db), relative to their normoglycemic db/ + mice. Hypoxia-ischemia was induced in 8-week-old male db/db and db/ + mice by the ligation of right common carotid artery followed by systemic hypoxia (8% O 2 : 92% N 2 ) for 17 mins. Mice were killed at specific intervals of reperfusion/recovery and the brains analyzed by in situ hybridization or total RNA isolation. In situ hybridization using bfl-1 (microglia) and glial fibrillary acidic protein (GFAP) (astrocytes) revealed expression of both bfl-1 and GFAP in the ipsilateral hemisphere at 4 h in the db/ + mice, which was delayed and minimal in the db/db mice. RNase protection assays showed a robust increase in expression of the proinflamatory cytokines tumor necrosis factor-a (TNFa), interleukin-1 IL-1a, and IL-1b mRNA in the db/ + mice at 6 to 8 h of reperfusion peaking at 8 to 12 h; in db/db mice expression was markedly delayed and diminished. Real-time-polymerase chain reaction (RT-PCR) confirmed the reduced and delayed expression TNFa, IL-1a, IL-1b, and the growth factors insulin-like growth factor-1 and ciliary neurotrophic factor in the db/db mice; enzyme-linked immunosorbent assays confirmed the reduced and delayed translation of IL-1b protein. These findings suggest that a compromised inflammatory response may underlie the greater infarct associated with diabetic db/db mice compared with their nondiabetic littermates following a hypoxic/ischemic insult.

Microglia and Monocyte-Derived Macrophages in Stroke

“…In vitro LPS stimulation of peritoneal macrophages from diabetic mice attenuated the inflammatory response [187]. The blunted inflammatory response in diabetic macrophages was also reported in db/db mice, with decreased microglial activation and proinflammatory cytokines in the stroked brain [188]. Microglial activation and the release of inflammatory factors are critical steps in eliciting a rapid inflammatory response in the context of injury.…”

“…These conditions are often associated with the exacerbation of ischemic outcomes and are predictive of worse recovery [186]. The inclusion of hyperlipidemia and diabetes in animal models of stroke has demonstrated that these conditions modulate postischemic inflammatory responses and lesion development [101,152,187,188]. In addition, increased inflammatory factors such as cytokines, chemokines, and adhesion molecules in peripheral monocytes/macrophages in these conditions suggest that peripheral immune status modulates CNS injury.…”

The PPAR-γ Agonist, Darglitazone, Restores Acute Inflammatory Responses to Cerebral Hypoxia–Ischemia in the Diabeticob/obMouse

“…Both type I and type II diabetic patients are two to six times more likely to experience a stroke than nondiabetic patients (Bonow and Gheorghiade, 2004); both morbidity and mortality after stroke are greatly enhanced, although the underlying mechanisms are still unknown. Initially, it was considered that preischemic hyperglycemia and consequent cerebral lactoacidosis were the primary cause (Folbergrova et al, 1992), however, we and others have indicated that additional factors have a significant role in the compromised recovery (Kumari et al, 2007;Nedergaard, 1987;Nedergaard and Diemer, 1987;Vannucci et al, 2001b;Zhang et al, 2004). Recently, we proposed that there is impairment in the acute inflammatory response in the diabetic db/db mouse after a unilateral cerebral hypoxic-ischemic (H/I) insult (Kumari et al, 2007;Zhang et al, 2004).…”

“…Blood glucose was measured on alternate days during treatment. After 1 week of treatment, cerebral hypoxia-ischemia was induced as reported earlier (Kumari et al, 2007;Vannucci et al, 2001a). Briefly, the right carotid artery was exposed and permanently ligated.…”

“…Initially, it was considered that preischemic hyperglycemia and consequent cerebral lactoacidosis were the primary cause (Folbergrova et al, 1992), however, we and others have indicated that additional factors have a significant role in the compromised recovery (Kumari et al, 2007;Nedergaard, 1987;Nedergaard and Diemer, 1987;Vannucci et al, 2001b;Zhang et al, 2004). Recently, we proposed that there is impairment in the acute inflammatory response in the diabetic db/db mouse after a unilateral cerebral hypoxic-ischemic (H/I) insult (Kumari et al, 2007;Zhang et al, 2004). This was manifested by a suppressed microglial and astrocytic activation coupled with a reduced and delayed expression of pro-and anti-inflammatory cytokines during the initial 12 h of recovery.…”