Endothelial cell dysfunction contributes to sepsis induced initiate immune response and the infiltration of immune cells into organs, resulting in organ injury. Heat shock protein A12B (HSPA12B) is predominantly expressed in endothelial cells. The present study investigated whether endothelial HSPA12B could regulate macrophage pro-inflammatory response during sepsis. Wild type (WT) and endothelial cell-specific HSPA12B deficient (HSPA12B–/–) mice were subjected to CLP sepsis. Mortality and cardiac function were monitored. Higher mortality, worsened cardiac dysfunction, and greater infiltrated macrophages in the myocardium and spleen were observed in HSPA12B–/– septic mice compared with the WT septic mice. The serum levels of TNF-α and IL-1β were higher and the levels of IL-10 were lower in HSPA12B–/– septic mice than in WT septic mice. Importantly, endothelial exosomes contain HSPA12B which can be uptaken by macrophages. Interestingly, endothelial exosomal HSPA12B significantly increases IL-10 levels and decreases TNF-α and IL-1β production in LPS-stimulated macrophages. Mechanistic studies show that endothelial exosomal HSPA12B downregulates NF-κB activation and nuclear translocation in LPS stimulated macrophages. These data suggest that endothelial HSPA12B plays a novel role in the regulation of macrophage pro-inflammatory response via exosomes during sepsis and that sepsis induced cardiomyopathy and mortality are associated with endothelial cell deficiency of HSPA12B.

Acute lung injury (ALI) is a critical manifestation of sepsis/septic shock. Heat shock protein A12B (HSPA12B), an endothelial cell-expressed heat shock protein, shows a negative regulation of lipopolysaccharide (LPS)-induced inflammation in myocardium and endothelial cells. However, it is unclear whether HSPA12B exerts protective effects against ALI during sepsis/septic shock. In this study, we treated HSPA12B transgenic mice (Tg) and wild type littermates (WT) with LPS for 6 h to induce endotoxemia. LPS treatment significantly caused pulmonary injuries as evidenced by microarchitecture destruction, vascular leakage and neutrophil recruitment in lungs of WT mice. However, the LPS-induced pulmonary injuries were significantly attenuated in Tg mice. Moreover, the LPS-induced activation of extracellular signal-regulated kinases (ERKs) and upregulation of intercellular adhesion molecule-1 (ICAM-1) and Cyclooxygenase-2 (Cox-2) were inhibited in Tg lungs compared with that in WT mice. Additionally, Tg lungs showed a significant lower level of vascular endothelial growth factor (VEGF) compared with WT mice. Our results demonstrate a pulmonary protective effect of HSPA12B against endotoxin challenge, which indicates management of HSPA12B expression could serve as a potential therapeutic target for ALI during sepsis/septic shock.

A zebrafish transcript dubbed GA2692 was initially identified via a whole-mount in situ hybridization screen for vessel specific transcripts. Its mRNA expression during embryonic development was detected in ventral hematopoietic and vasculogenic mesoderm and later throughout the vasculature up to 48 hours post fertilization. Morpholino-mediated knockdown of GA2692 in embryos resulted in multiple defects in vasculature, particularly, at sites undergoing active capillary sprouting: the intersegmental vessels, sub-intestinal vessels and the capillary sprouts of the pectoral fin vessel. During the course of these studies, a homology search indicated that GA2692 is the zebrafish orthologue of mammalian HspA12B, a distant member of the heat shock protein 70 (Hsp70) family. By a combination of northern blot and realtime PCR analysis, we showed that HspA12B is highly expressed in human endothelial cells in vitro. Knockdown of HspA12B by small interfering RNAs (siRNAs) in human umbilical vein endothelial cells blocked wound healing, migration and tube formation, whereas overexpression of HspA12B enhanced migration and accelerated wound healing - data that are consistent with the in vivo fish phenotype obtained in the morpholino-knockdown studies. Phosphorylation of Akt was consistently reduced by siRNAs against HspA12B. Overexpression of a constitutively active form of Akt rescued the inhibitory effects of knockdown of HspA12B on migration of human umbilical vein endothelial cells. Collectively, our data suggests that HspA12B is a highly endothelial-cell-specific distant member of the Hsp70 family and plays a significant role in endothelial cells during development and angiogenesis in vitro, partially attributable to modulation of Akt phosphorylation.

OBJECTIVE - HSPA12B is the newest member of HSP70 family of proteins and is enriched in atherosclerotic lesions. This study focused on HSPA12B expression in mice and its involvement in angiogenesis. METHODS AND RESULTS - The expression of HSPA12B in mice and cultured cells was studied by: (1) Northern blot; (2) in situ hybridization; (3) immunostaining with HSPA12B-specific antibodies; and (4) expressing Enhanced-Green-Fluorescent-Protein under the control of the HSPA12B promoter in mice. The function of HSPA12B was probed by an in vitro angiogenesis assay (Matrigel) and a migration assay. Interacting proteins were identified through a yeast two-hybrid screening. HSPA12B is predominantly expressed in vascular endothelium and induced during angiogenesis. In vitro angiogenesis and migration are inhibited in human umbilical vein endothelial cells in the presence of HSPA12B-neutralizing antibodies. HSPA12B interacts with multiple proteins in yeast 2-hybrid system. CONCLUSIONS - We provide the first evidence to our knowledge that the HSPA12B is predominantly expressed in endothelial cells, required for angiogenesis, and interacts with known angiogenesis regulators. We postulate that HSPA12B provides a new mode of angiogenesis regulation and a novel therapeutic target for angiogenesis-related diseases.

Previously, we cloned Heat shock protein A12B (HspA12B), the newest member of a recently defined subfamily of proteins distantly related to the Hsp70 family that are enriched in atherosclerotic lesions. We have found that HspA12B is predominantly expressed in vascular endothelium, and that it is involved in angiogenesis which we probed by in vitro angiogenesis assays (Matrigel), migration assays and Directed In Vivo Angiogenesis Assay (DIVAA). Hsp70s are molecular chaperones that are inducible by stress and have been found to be anti-apoptotic (Li et al. 2000; Nylandsted et al. 2000; Garrido et al. 2001). Because of its homology to Hsp70, we propose that it is the first endothelial-specific chaperone that is required for angiogenesis and interacts with known angiogenesis regulators. To begin to understand the molecular mechanisms underlying the role of HspA12B in angiogenesis, we turned our attention to identifying proteins that are involved in angiogenesis and also interact with HspA12B. Through the use of a yeast two-hybrid (Y2H) system HspA12B was found to interact with a known angiogenesis regulator, A Kinase Anchoring Protein 12 (AKAP12). This interaction was confirmed by co-immunoprecipitation and by colocalization. In primary human umbilical vein endothelial cells (HUVECs), shRNA mediated HspA12B knockdown increased AKAP12 levels and decreased VEGF by more than 75%, whereas HspA12B over-expression decreased AKAP12 and more than doubled VEGF levels. We further identified a 32-Amino Acid (32-AA) domain in AKAP12 that mediates interaction with HspA12B. Over-expression of this 32-AA domain in HUVECs disrupted the HspA12B-AKAP12 interaction and decreased VEGF expression suggesting the importance of the HspA12B-AKAP12 interaction in regulating VEGF. This is the first evidence that HspA12B promotes angiogenesis resulting in up-regulation of VEGF by suppressing AKAP12. Consistent with the proposed role in angiogenesis, HspA12B was also found to be increased in endothelial cells (ECs) by angiogenic stresses including hypoxia and shearing stress while knockdown of HspA12B abolished hypoxia-induced tubule formation. This work provides new insight into the mechanisms controlling angiogenesis by providing the first example of an EC-specific molecular chaperone that acts as a regulator of angiogenesis and lays the foundation for future studies of HspA12B-derived therapeutics for angiogenesis related diseases.

Heat shock protein A12B (HSPA12B) is predominately expressed in endothelial cells (ECs) and has been reported to protect against cardiac dysfunction from endotoxemia or myocardial infarction. This study investigated the mechanisms by which endothelial HSPA12B protects polymicrobial sepsis–induced cardiomyopathy. Wild-type (WT) and endothelial HSPA12B knockout (HSPA12B–/–) mice were subjected to polymicrobial sepsis induced by cecal ligation and puncture (CLP). Cecal ligation and puncture sepsis accelerated mortality and caused severe cardiac dysfunction in HSPA12B–/– mice compared with WT septic mice. The levels of adhesion molecules and the infiltrated immune cells in the myocardium of HSPA12B–/– septic mice were markedly greater than in WT septic mice. The levels of microRNA-126 (miR-126), which targets adhesion molecules, in serum exosomes from HSPA12B–/– septic mice were significantly lower than in WT septic mice. Transfection of ECs with adenovirus expressing HSPA12B significantly increased miR-126 levels. Increased miR-126 levels in ECs prevented LPS-stimulated expression of adhesion molecules. In vivo delivery of miR-126 carried by exosomes into the myocardium of HSPA12B–/– mice significantly attenuated CLP sepsis increased levels of adhesion molecules, and improved CLP sepsis–induced cardiac dysfunction. The data suggest that HSPA12B protects against sepsis-induced severe cardiomyopathy via regulating miR-126 expression which targets adhesion molecules, thus decreasing the accumulation of immune cells in the myocardium.

Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine. Stroke is the leading cause of disability worldwide. HSPA12B, a heat-shock protein recently identified expression specifically in endothelial cells, is able to promote angiogenesis. Here, we have investigated its effects on functional recovery at chronic phase of ischaemic stroke. Ischaemic stroke was induced by 60 min. of middle cerebral artery occlusion in transgenic mice with overexpression of HSPA12B (HSPA12B Tg) and wild-type littermates (WT). HSPA12B Tg mice demonstrated a significant higher survival rate than WT mice within 28 days post-stroke. Significant improved neurological functions, increased spontaneous locomotor activity and decreased anxiety were detected inHSPA12B Tg mice compared with WT controls within 21 days post-stroke. Stroke-induced hippocampal degeneration was attenuated in HSPA12B Tg mice examined at day 28 post-stroke. Interestingly, HSPA12B Tg mice showed enhanced peri-infarct angiogenesis (examined 28 days post-stroke) and hippocampal neurogenesis (examined 7 days post-stroke), respectively, compared to WT mice. The stroke-induced eNOS phosphorylation and TGF-β1 expression were augmented in HSPA12B Tg mice. However, administration with eNOS inhibitor L-NAME diminished the HSPA12B-induced protection in neurological functional recovery and mice survival post-stroke. The data suggest that HSPA12B promoted functional recovery and survival after stroke in an eNOS-dependent mechanism. Targeting HSPA12B expression may have a therapeutic potential for the stroke-evoked functional disability and mortality.

AimsHSPA12B is a newly discovered and endothelial-cell-specifically expressed heat shock protein. We have reported recently that overexpression of HSPA12B increased endothelial nitric oxide synthase (eNOS) expression in mouse cardiac tissues during endotoxemia. Endothelial NOS has been shown to protect heart from ischaemic injury. We hypothesized that overexpression of HSPA12B will attenuate cardiac dysfunction and remodelling after myocardial infarction (MI) through an eNOS-dependant mechanism.Methods and resultsMI was induced by permanent ligation of the left anterior descending coronary artery in the transgenic mice (Tg) overexpressing hspa12b gene and its wild-type (WT) littermates. Echocardiographic analysis revealed that Tg mice exhibited improvements in cardiac dysfunction and remodelling at 1 and 4 weeks after MI. These improvements were accompanied by a significant decrease in cardiomyocyte apoptosis and increase in capillary and arteriolar densities. Significant up-regulation of eNOS, VEGF, Ang-1, and Bcl-2 was also observed in Tg hearts compared with WT hearts after MI. However, pharmacological inhibition of eNOS abolished the HSPA12B-induced decrease in cardiomyocyte apoptosis and increase in capillary formation after MI. Most importantly, inhibition of eNOS abrogated the protection of HSPA12B against cardiac dysfunction and remodelling after MI.ConclusionsThese data demonstrate for the first time that the overexpression of HSPA12B attenuates cardiac dysfunction and remodelling after MI. This action of HSPA12B was mediated, at least in part, by prevention of cardiomyocyte apoptosis and promotion of myocardial angiogenesis via an eNOS-dependent mechanism. HSPA12B could be a novel target for the management of patients with post-MI cardiac dysfunction and remodelling.

Background and purpose: HSPA12B is a newly discovered member of the Hsp70 family proteins. This study investigated the effects of HSPA12B on focal cerebral ischemia/reperfusion (I/R) injury in mice. Methods: Transgenic mice overexpressing human HSPA12B (Tg) and wild-type littermates (WT) were subjected to 60. min of middle cerebral artery occlusion to induce ischemia and followed by reperfusion (I/R). Neurological deficits, infarct volumes and neuronal death were examined at 6 and 24. hrs after reperfusion. Blood-brain-barrier (BBB) integrity and activated cellular signaling were examined at 3. hrs after reperfusion. Results: After cerebral I/R, Tg mice exhibited improvement in neurological deficits and decrease in infarct volumes, when compared with WT I/R mice. BBB integrity was significantly preserved in Tg mice following cerebral I/R. Tg mice also showed significant decreases in cell injury and apoptosis in the ischemic hemispheres. We observed that overexpression of HSPA12B activated PI3K/Akt signaling and suppressed JNK and p38 activation following cerebral I/R. Importantly, pharmacological inhibition of PI3K/Akt signaling abrogated the protection against cerebral I/R injury in Tg mice. Conclusions: The results demonstrate that HSPA12B protects the brains from focal cerebral I/R injury. The protective effect of HSPA12B is mediated though a PI3K/Akt-dependent mechanism. Our results suggest that HSPA12B may have a therapeutic potential against ischemic stroke.

AimsHSPA12B is a newly discovered and endothelial-cell-specifically expressed heat shock protein. We have reported recently that overexpression of HSPA12B increased endothelial nitric oxide synthase (eNOS) expression in mouse cardiac tissues during endotoxemia. Endothelial NOS has been shown to protect heart from ischaemic injury. We hypothesized that overexpression of HSPA12B will attenuate cardiac dysfunction and remodelling after myocardial infarction (MI) through an eNOS-dependant mechanism.Methods and resultsMI was induced by permanent ligation of the left anterior descending coronary artery in the transgenic mice (Tg) overexpressing hspa12b gene and its wild-type (WT) littermates. Echocardiographic analysis revealed that Tg mice exhibited improvements in cardiac dysfunction and remodelling at 1 and 4 weeks after MI. These improvements were accompanied by a significant decrease in cardiomyocyte apoptosis and increase in capillary and arteriolar densities. Significant up-regulation of eNOS, VEGF, Ang-1, and Bcl-2 was also observed in Tg hearts compared with WT hearts after MI. However, pharmacological inhibition of eNOS abolished the HSPA12B-induced decrease in cardiomyocyte apoptosis and increase in capillary formation after MI. Most importantly, inhibition of eNOS abrogated the protection of HSPA12B against cardiac dysfunction and remodelling after MI.ConclusionsThese data demonstrate for the first time that the overexpression of HSPA12B attenuates cardiac dysfunction and remodelling after MI. This action of HSPA12B was mediated, at least in part, by prevention of cardiomyocyte apoptosis and promotion of myocardial angiogenesis via an eNOS-dependent mechanism. HSPA12B could be a novel target for the management of patients with post-MI cardiac dysfunction and remodelling.