Venous thromboembolism (VTE), caused by altered hemostasis, remains the third most common cause of mortality among all cardiovascular conditions. In addition to established genetic and acquired risk factors, low-oxygen environments also predispose otherwise healthy individuals to VTE. Although disease etiology appears to entail perturbation of hemostasis pathways, the key molecular determinants during immediate early response remain elusive. Using an established model of venous thrombosis, we here show that systemic hypoxia accelerates thromboembolic events, functionally stimulated by the activation of nucleotide binding domain, leucine-rich-containing family, pyrin domain containing 3 (NLRP3) inflammasome complex and increased IL-1β secretion. Interestingly, we also show that the expression of NLRP3 is mediated by hypoxia-inducible factor 1-alpha (HIF-1α) during these conditions. The pharmacological inhibition of caspase-1, in vivo knockdown of NLRP3, or HIF-1α other than IL-1β-neutralizing antibodies attenuated inflammasome activation and curtailed thrombosis under hypoxic conditions. We extend the significance of these preclinical findings by studying modulation of this pathway in patients with altitude-induced venous thrombosis. Our results demonstrate distinctive, increased expression of NLRP3, caspase-1, and IL-1β in individuals with clinically established venous thrombosis. We therefore propose that an early proinflammatory state in the venous milieu, orchestrated by the HIF-induced NLRP3 inflammasome complex, is a key determinant of acute thrombotic events during hypoxic conditions.

Key Points• Hypoxia induces altered platelet proteome/reactivity, which correlates with a prothrombotic phenotype.• CAPNS1-dependent calpain activity in platelet activation cascade is associated with hypoxia-induced thrombogenesis.Oxygen-compromised environments, such as high altitude, air travel, and sports, and pathological conditions, such as solid tumors, have been suggested to be prothrombotic. Despite the indispensable role of platelets in thrombus formation, the studies linking hypoxia, platelet reactivity, and thrombus formation are limited. In the present study, platelet proteome/reactivity was analyzed to elucidate the acute hypoxia-induced prothrombotic phenotype. Rats exposed to acute simulated hypoxia (282 torr/8% oxygen) demonstrated a decreased bleeding propensity and increased platelet reactivity. Proteomic analysis of hypoxic platelets revealed 27 differentially expressed proteins, including those involved in coagulation. Among these proteins, calpain small subunit 1, a 28-kDa regulatory component for calpain function, was significantly upregulated under hypoxic conditions. Moreover, intraplatelet Ca 21 level and platelet calpain activity were also found to be in accordance with calpain small subunit 1 expression. The inhibition of calpain activity demonstrated reversal of hypoxia-induced platelet hyperreactivity. The prothrombotic role for calpain was further confirmed by an in vivo model of hypoxia-induced thrombosis. Interestingly, patients who developed thrombosis while at extreme altitude had elevated plasma calpain activities and increased soluble P-selectin level. In summary, this study suggests that augmented calpain activity is associated with increased incidence of thrombosis under hypoxic environments. (Blood. 2014;123(8):1250-1260

Venous thromboembolism (VTE), a multi-factorial disease, is the third most common cardiovascular disease. Established genetic and acquired risk factors are responsible for the onset of VTE. High altitude (HA) also poses as an additional risk factor, predisposing individuals to VTE; however, its molecular mechanism remains elusive. This study aimed to identify genes/pathways associated with the pathophysiology of deep vein thrombosis (DVT) at HA. Gene expression profiling of DVT patients, who developed the disease, either at sea level or at HA-DVT locations, resulted in differential expression of 378 and 875 genes, respectively. Gene expression profiles were subjected to bioinformatic analysis, followed by technical and biological validation of selected genes using quantitative reverse transcription-polymerase chain reaction. Both gene ontology and pathway analysis showed enrichment of genes involved in haemostasis and platelet activation in HA-DVT patients with the most relevant pathway being 'response to hypoxia'. Thus, given the environmental condition the differential expression of hypoxia-responsive genes (angiogenin, ribonuclease, RNase A family, 5; early growth response 1; lamin A; matrix metallopeptidase 14 [membrane-inserted]; neurofibromin 1; PDZ and LIM domain 1; procollagen-lysine 1, 2-oxoglutarate 5-dioxygenase 1; solute carrier family 6 [neurotransmitter transporter, serotonin], member 4; solute carrier family 9 [sodium/hydrogen exchanger], member 1; and TEK tyrosine kinase, endothelial) in HA-DVT could be a determining factor to understand the pathophysiology of DVT at HA.

Spontaneous retroperitoneal haematoma (SRH) can be a life-threatening emergency presenting with hypovolaemic shock. SRH has been rarely reported with May-Thurner syndrome (MTS) where it occurs due to rupture of the iliac vein or venous collaterals. We report a case of MTS that presented with deep venous thrombosis of the left lower limb complicated by bilateral pulmonary embolism (PE) and a large pelvic haematoma. The simultaneous occurrence of a large pelvic haematoma and PE offered a therapeutic challenge. Successful endovascular management of the case is discussed in this report.

Key PointsHA exposure alters hemostatic systems and contributes to the onset of VTE at a younger age. Aggravated disruption of coagulation, platelet, and endothelial function differentiates HA-induced VTE from VTE on the plains.

Background: The pathophysiology of Deep vein thrombosis (DVT) is considered as multifactorial, where thrombus formation is interplay of genetic and acquired risk factors. A little is known about the expression profile and roles of lncRNAs in human subjects developing DVT at high altitude. Methods: Using RNAseq, we compared peripheral blood mRNA and lncRNA expression profile in human High Altitude deep Vein Thrombosis (HA-DVT) patients with high altitude control subjects. We used DESeq to identify differentially expressed (DE) genes. We annotated the long noncoding RNAs using NONCODE 3.0 database. In silico putative lncRNA-miRNA association study unravels the endogenous miRNA sponge associated with our candidate lncRNAs. These findings were validated by siRNA knockdown assay of the candidate lncRNAs conducted in primary endothelial cells. Results: We identified 1524 DE mRNA and 973 DE lncRNAs. Co-expressed protein-coding genes analysis resulted in a list of 722 coexpressed protein-coding genes with a Pearson correlation coefficients >0.7. The functional annotation of co-expressed genes and putative proteins revealed their involvement in the hypoxia, immune response and coagulation cascade. Through its miRNA response elements (MREs) to compete for miR-143 and miR-15, lncRNA-LINC00659 and UXT-AS1 regulates the expression of prothrombotic genes. Furthermore, in vitro RNA interference (siRNA) simultaneously suppressed lncRNAs and target gene mRNA level. Conclusions: This transcriptome profile describes novel potential mechanisms of interaction between lncRNAs, the coding genes, miRNAs and regulatory transcription factors that define the thrombotic signature and may be used in establishing lncRNAs as biomarker in HA-DVT.

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Invasive aspergillosis is a severe fungal infection that primarily affects immunocompromised patients. We report a case of invasive aspergillosis presenting as a febrile respiratory infection with a cardiac mass in an immunocompetent patient. Excision of the intracardiac mass followed by histopathological examination confirmed the diagnosis. The patient was managed with voriconazole, to which he responded well. Rare occurrence of an intracardiac mass with systemic aspergillosis in an immunocompetent host is discussed in this case report.