Methods: Stroke-prone spontaneously hypertensive rats (SHRSP), a model of genetic hypertension and stroke, were continually injected with a bacterial cell suspension of Escherichia coli or Porphyromonas gingivalis.
Results: Systolic blood pressure was moderately elevated in SHRSP prior to stroke onset following the continual injection of either bacterial suspension. Stroke onset occurred significantly earlier in SHRSP injected with either bacteria compared to uninjected controls. Furthermore, the injection of lipopolysaccharides (LPS), a major pathogenic factor of gram-negative rods, displayed similar effects. Decreased body weight and paralysis in the forelimb were observed during stroke onset in all SHRSP, excluding cases of sudden death. In contrast, paralysis in the hindlimb, piloerection, hypokinesis, and hyperkinesis were observed only in SHRSP injected with LPS during stroke onset and SHRSP without injection, during the late survival period, but not during stroke onset. Moreover, sudden death was a symptom of stroke onset only in LPS-injected SHRSP. The serum levels of thiobarbituric acid reactive substance, a marker of oxidative stress, significantly increased in LPS-injected SHRSP compared to the uninjected group.
Conclusions: These results suggest that continual gram-negative bacterial challenge induces accelerated stroke onset in SHRSP, probably caused by oxidative stress responses derived from LPS.