Publications

To determine the value of human immunodeficiency virus type 1 (HIV-1) RNA level in distinguishing HIV-associated nephropathy from non-HIV-associated nephropathy renal pathological conditions, we retrospectively compared renal histopathological findings for 86 HIV-infected patients according to HIV-1 RNA levels. We found that HIV-associated nephropathy was unlikely among patients with HIV-1 RNA levels <400 copies/mL. Hypertensive vascular disease surpassed HIV-associated nephropathy as the most common renal pathological finding among the entire cohort. HIV-1 RNA level did not correlate with renal survival.

OBJECTIVE

N, N-Dimethylsphingosine (DMS) is recognized as an inhibitor of sphingosine kinase (SphK), a key enzyme responsible for the formation of sphingosine-1-phosphate (S1P). We previously showed that S1P was cardioprotective and that SphK was critical for myocardial ischemic preconditioning. Although DMS is an endogenous sphingolipid, its effect on cardiac function and cardioprotection at low concentration has not been studied.

METHODS

In Langendorff-perfused wild-type and protein kinase C (PKC)epsilon-null mouse hearts, cardiac function, infarction size, and SphK activity were measured.

RESULTS

Pretreatment with 0.3 microM and 1 microM DMS for 10 min protected against ischemia/reperfusion injury. Cardiac function (LVDP, +/-dP/dtmax) was improved and infarction size was reduced. The cardiac protection induced by DMS was abolished in PKCepsilon-null mouse hearts. Administration of 1 microM DMS ex vivo increased cytosolic SphK activity. This enhanced SphK activity was abolished in PKCepsilon-null mouse hearts. DMS also increased PKCepsilon translocation from the particulate to the cytosolic fraction with no effect on PKCalpha distribution. Co-immunoprecipitation showed that SphK1 interacted with PKCepsilon phosphorylated on Ser729. DMS also increased cytosolic Akt phosphorylation (Ser 473) and Akt translocation from a Triton-insoluble fraction to the cytosol.

CONCLUSIONS

DMS has a biphasic effect on cardioprotection. Higher concentrations (10 microM) are inhibitory, whereas a low concentration (0.3 microM and 1 microM) of DMS protects murine hearts against ischemia/reperfusion injury. DMS activates SphK in the cytosol via a PKCepsilon dependent mechanism. The PKCepsilon-SphK-S1P-Akt pathway is involved in the cardiac protection induced by DMS.

Myocardial remodeling after myocardial infarction (MI) is associated with increased levels of the matrix metalloproteinases (MMPs). Levels of two MMP species, MMP-2 and MMP-9, are increased after MI, and transgenic deletion of these MMPs attenuates post-MI left ventricular (LV) remodeling. This study characterized the spatiotemporal patterns of gene promoter induction for MMP-2 and MMP-9 after MI. MI was induced in transgenic mice in which the MMP-2 or MMP-9 promoter sequence was fused to the beta-galactosidase reporter, and reporter level was assayed up to 28 days after MI. Myocardial localization with respect to cellular sources of MMP-2 and MMP-9 promoter induction was examined. After MI, LV diameter increased by 70% (P < 0.05), consistent with LV remodeling. beta-Galactosidase staining in MMP-2 reporter mice was increased by 1 day after MI and increased further to 64 +/- 6% of LV epicardial area by 7 days after MI (P < 0.05). MMP-2 promoter activation occurred in fibroblasts and myofibroblasts in the MI region. In MMP-9 reporter mice, promoter induction was detected after 3 days and peaked at 7 days after MI (53 +/- 6%, P < 0.05) and was colocalized with inflammatory cells at the peri-infarct region. Although MMP-2 promoter activation was similarly distributed in the MI and border regions, activation of the MMP-9 promoter was highest at the border between the MI and remote regions. These unique findings visually demonstrated that activation of the MMP-2 and MMP-9 gene promoters occurs in a distinct spatial relation with reference to the MI region and changes in a characteristic time-dependent manner after MI.