Docosahexaenoic acid confers neuroprotection in a rat model of perinatal hypoxia-ischemia potentiated by Escherichia coli lipopolysaccharide-induced systemic inflammation

Abstract

Objective: Lipopolysaccharide pretreatment potentiates hypoxic ischemic injury. We hypothesized that docosahexaenoic acid pretreatment would improve function and reduce brain volume loss in this rat model of perinatal brain injury and inflammation.

Study design: Seven-day-old rats were divided into 3 groups: intraperitoneal docosahexaenoic acid 1 mg/kg and lipopolysaccharide 0.1 mg/kg, 25% albumin and lipopolysaccharide, and normal saline. Injections were given 2.5 hours before carotid ligation, followed by 90 minutes 8% O2. Rats underwent sensorimotor function testing and brain volume loss assessment on postnatal day 14.

Results: Docosahexaenoic acid pretreatment improved vibrissae forepaw placing scores compared with albumin/lipopolysaccharide (mean+/-standard deviation weighted score/20: 17.72+/-0.92 docosahexaenoic acid/lipopolysaccharide vs 13.83+/-0.82 albumin/lipopolysaccharide; P<.007). Albumin/lipopolysaccharide rats scores were worse than those of the normal saline/normal saline rats (13.83+/-0.82 vs 17.21+/-0.71; P=.076). No significant differences in brain volume loss were observed among groups.

Conclusion: Lipopolysaccharide inflammatory stimulation in conjunction with hypoxic ischemic resulted in poorer function than hypoxic ischemic alone. Docosahexaenoic acid pretreatment had significantly improved function in neonatal rats exposed to lipopolysaccharide and hypoxic ischemic.

Figure 1. DHA pretreatment attenuates forepaw placing deficits among hypoxic ischemic pups exposed to LPS pretreatment

Vibrissae-stimulated forepaw placing test results in control groups (that received normal saline followed by normal saline) and treatment groups (that received DHA 1mg/kg or Albumin followed by E. coli lipopolysaccharide inflammation) prior to undergoing right (R) carotid ligation followed by 90 minutes of hypoxia at 8% oxygen on postnatal day (P) 7. Testing was performed on P14 (10 trials/side). The y-axis = weighted response score in which complete forepaw placing on stimulus surface received score of 2 and partial response (i.e. forepaw motion without placing on stimulus surface) received score of 1. Best possible weighted score is 20. Boxes= interquartile range; horizontal bars=medians; whiskers=SE. They extend to data points no more than 1.5 width of box. All animals consistently responded to R vibrissae stimulation with appropriate R paw placement. Impairment of left (L) paw placement in response to L vibrissae stimulation was seen in Albumin/LPS rats compared to normal saline/normal saline rats. Among LPS pretreated groups, performance was significantly better in the DHA/LPS treatment group when compared to Albumin/LPS (P=.007; Tukey-Kramer test).