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Pathophysiological, epidemiological, and genetic studies provide strong evidence that lipoprotein(a) [Lp(a)] is a causal mediator of cardiovascular disease (CVD) and calcific aortic valve disease (CAVD). Specific therapies to address Lp(a)-mediated CVD and CAVD are in clinical development. Due to knowledge gaps, the National Heart, Lung, and Blood Institute organized a working group that identified challenges in fully understanding the role of Lp(a) in CVD/CAVD. These included the lack of research funding, inadequate experimental models, lack of globally standardized Lp(a) assays, and inadequate understanding of the mechanisms underlying current drug therapies on Lp(a) levels. Specific recommendations were provided to facilitate basic, mechanistic, preclinical, and clinical research on Lp(a); foster collaborative research and resource sharing; leverage expertise of different groups and centers with complementary skills; and use existing National Heart, Lung, and Blood Institute resources. Concerted efforts to understand Lp(a) pathophysiology, together with diagnostic and therapeutic advances, are required to reduce Lp(a)-mediated risk of CVD and CAVD.

Hutchinson-Gilford progeria syndrome (HGPS), a devastating premature aging disease, is caused by a point mutation in the lamin A gene (LMNA). This mutation constitutively activates a cryptic splice donor site, [...]

Vascular proliferative diseases are characterized by VSMC proliferation and migration. Kinase interacting with stathmin (KIS) targets 2 key regulators of cell proliferation and migration, the cyclin-dependent kinase inhibitor [p27.sup.Kip1] and the microtubule-destabilizing protein stathmin. Phosphorylation of [p27.sup.Kip1] by KIS leads to cell-cycle progression, whereas the target sequence and the physiological relevance of KIS-mediated stathmin phosphorylation in VSMCs are unknown. Here we demonstrated that vascular wound repair in KIS-/- mice resulted in accelerated formation of neointima, which is composed predominantly of VSMCs. Deletion of KIS increased VSMC migratory activity and cytoplasmic tubulin destabilizing activity, but abolished VSMC proliferation through the delayed nuclear export and degradation of [p27.sup.Kip1]. This promigratory phenotype resulted from increased stathmin protein levels, caused by a lack of KIS-mediated stathmin phosphorylation at serine 38 and diminished stathmin protein degradation. Downregulation of stathmin in KIS-/- VSMCs fully restored the phenotype, and stathmin-deficient mice demonstrated reduced lesion formation in response to vascular injury. These data suggest that KIS protects against excessive neointima formation by opposing stathmin-mediated VSMC migration and that VSMC migration represents a major mechanism of vascular wound repair, constituting a relevant target and mechanism for therapeutic interventions., Introduction Vascular remodeling and wound repair constitute complex mechanisms aimed at restoration of vessel integrity and vessel function. This involves cells within the vessel wall, predominantly VSMCs, and the recruitment [...]

Cyclin-dependent kinase inhibitors, including [p21.sup.Cip1], are implicated in cell turnover and are active players in cardiovascular wound repair. Here, we show that [p21.sup.Cip1] orchestrates the complex interactions between local vascular and circulating immune cells during vascular wound repair. In response to femoral artery mechanical injury, mice with homozygous deletion of [p21.sup.Cip1] displayed accelerated proliferation of VSMCs and increased immune cell infiltration. BM transplantation experiments indicated that local [p21.sup.Cip1] plays a pivotal role in restraining excessive proliferation during vascular wound repair. Increased local vascular stromal cell--derived factor-1 (SDF-1) levels were observed after femoral artery injury in p21+/+ and p21-/- mice, although this was significantly greater in p21-/- animals. In addition, disruption of SDF-1/CXCR4 signaling inhibited the proliferative response during vascular remodeling in both p21+/+ and p21-/- mice. We provide evidence that the JAK/STAT signaling pathway is an important regulator of vascular SDF-1 levels and that [p21.sup.Cip1] inhibits STAT3 binding to the STAT-binding site within the murine SDF-1 promoter. Collectively, these results suggest that [p21.sup.Cip1] activity is essential for the regulation of cell proliferation and inflammation after arterial injury in local vascular cells and that the SDF-1/CXCR4 signaling system is a key mediator of vascular proliferation in response to injury., Introduction Vascular wound repair is controlled by the interaction of local vascular cells (endothelial and smooth muscle) and infiltrating inflammatory cells (macrophages, neutrophils, and lymphocytes). Particularly during arterial wound healing, [...]

Hutchinson-Gilford progeria syndrome (HGPS) is the most dramatic form of human premature aging. Death occurs at a mean age of 13 years, usually from heart attack or stroke. Almost all cases of HGPS are caused by a de novo point mutation in the lamin A (LMNA) gene that results in production of a mutant lamin A protein termed progerin. This protein is permanently modified by a lipid farnesyl group, and acts as a dominant negative, disrupting nuclear structure. Treatment with farnesyltransferase inhibitors (FTls) has been shown to prevent and even reverse this nuclear abnormality in cultured HGPS fibroblasts. We have previously created a mouse model of HGPS that shows progressive loss of vascular smooth muscle cells in the media of the large arteries, in a pattern that is strikingly similar to the cardiovascular disease seen in patients with HGPS. Here we show that the dose-dependent administration of the FTI tipifarnib (R115777, Zarnestra) to this HGPS mouse model can significantly prevent both the onset of the cardiovascular phenotype as well as the late progression of existing cardiovascular disease. These observations provide encouraging evidence for the current clinical trial of FTIs for this rare and devastating disease. [ABSTRACT FROM AUTHOR]

The cyclin-dependent kinase inhibitor p27Kip1 arrests cell cycle progression through G1/S phases and is regulated by phosphorylation of serine/ threonine residues. Recently, we identified the serine/ threonine kinase, KIS, which phosphorylates p27Kip1 on serine 10 leading to nuclear export of p27Kip1 and protein degradation. However, the molecular mechanisms of transcriptional activation of the human KIS gene and its biological activity are not known. We mapped the transcription initiation site ~116 bp 5' to the translation start site, and sequences extending to -141 were sufficient for maximal promoter activity. Mutation in either of two Ets-binding sites in this region resulted in an approximately 75-80% decrease in promoter activity. These sites form at least 3 specific complexes, which contained GA-binding protein (GABP). Knocking down GABPα by siRNA in vascular smooth muscle cells (VSMCs) diminished KIS gene expression and reduced cell migration. Correspondingly, in serum stimulated GABPα-deficient mouse embryonic fibroblasts (MEFs), KIS gene expression was also significantly reduced, which was associated with an increase in p27Kip1 protein levels and a decreased percentage of cells in S-phase. Consistent with these findings, following vascular injury in vivo, GABPα-heterozygous mice demonstrated reduced KIS gene expression within arterial lesions and these lesions were significantly smaller compared to GABP+/+ mice. In summary, serum-responsive GABP binding to Ets-binding sites activates the KIS promoter, leading to KIS gene expression, cell migration, and cell cycle progression. [ABSTRACT FROM AUTHOR]

Abstract: The G1/S phase restriction point is a critical checkpoint that interfaces between the cell cycle regulatory machinery and DNA replicator proteins. Here, we report a novel function for the cyclin-dependent kinase inhibitor p27Kip1 in inhibiting DNA replication through its interaction with MCM7, a DNA replication protein that is essential for initiation of DNA replication and maintenance of genomic integrity. We find that p27Kip1 binds the conserved minichromosome maintenance (MCM) domain of MCM7. The proteins interact endogenously in vivo in a growth factor-dependent manner, such that the carboxyl terminal domain of p27Kip1 inhibits DNA replication independent of its function as a cyclin-dependent kinase inhibitor. This novel function of p27Kip1 may prevent inappropriate initiation of DNA replication prior to S phase. [Copyright &y& Elsevier]

The cyclin-dependent kinase inhibitors are key regulators of cell cycle progression. Although implicated in carcinogenesis, they inhibit the proliferation of a variety of normal cell types, and their role in diverse human diseases is not filly understood. Here, we report that p27Kip1 plays a major role in cardiovascular disease through its effects on the proliferation of bone marrow-derived (BM-derived) immune cells that migrate into vascular lesions. Lesion formation after mechanical arterial injury was markedly increased in mice with homozygous deletion of p27Kip1, characterized by prominent vascular infiltration by immune and inflammatory cells. Vascular occlusion was substantially increased when BM-derived cells from p27-/- mice repopulated vascular lesions induced by mechanical injury in p27-/- recipients, in contrast to p27+/+ BM donors. To determine the contribution of immune cells to vascular injury, transplantation was performed with BM derived from RAG-/- and RAG+/+ mice. RAG+/+ BM markedly exacerbated vascular proliferative lesions compared with what was found in RAG+ donors. Taken together, these findings suggest that vascular repair and regeneration is regulated by the proliferation of BM-derived hematopoietic and nonhematopoietic cells through a p27Kip1 dependent mechanism and that immune cells largely mediate these effects. [ABSTRACT FROM AUTHOR]