FIG. 4.

Dynamics of HO-1 mRNA expression in organ-specific micro- and macrovascular ECs infected with R. rickettsii. Total RNA (8 μg) from uninfected ECs (Control) or those infected with R. rickettsii for 3 to 21 h were processed for Northern blot analysis to determine the level of HO-1 transcriptional activation. Blots were first probed with a cDNA probe specific for human HO-1, followed by a GAPDH probe to normalize for potential variations in RNA loading among different samples. Results of a representative blot obtained from infected HPMECs are shown in panel A. The detailed densitometric analysis of changes in steady-state levels of HO-1 transcript due to R. rickettsii infection of different types of ECs is presented as the mean fold induction over the basal level of 1 (B). The data are presented as the mean ± standard error of three independent experiments (n ≥ 3). The asterisks indicate statistically significant differences in HO-1 mRNA expression relative to the corresponding uninfected controls.