Arterial and Venous Thrombosis From Delayed-Onset Heparin-Induced Thrombocytopenia.

Heparin Induced Thrombocytopenia (HIT) is a life threatening condition which is caused due to antibody formation following exposure to heparin or heparin products. It occurs due to the formation of Platelet Factor 4 antibodies (PF4). HIT is classified into 3 categories based on the duration between heparin exposure and onset of drop in platelet counts. A less common form of HIT is delayed onset HIT which occurs more than 9 days after exposure to heparin or heparin products. In this report we would like to present a rare case of delayed onset HIT which occurred in our patient who presented with rhabdomyolysis and Non ST elevation myocardial infraction (NSTEMI); which resulted in limb ischemia which needed to be treated by amputation of the affected area. We also highlight further management of patients who have thrombotic disease in the setting of HIT and review literature of how heparin or heparin products can be reintroduced in such patient who cannot be managed by other anticoagulation.

A Case of COVID-19 Vaccine-Induced Thrombotic Thrombocytopenia.

SARS-CoV-2, which originated in China in late 2019, has spread rapidly resulting in a global pandemic. Multiple vaccines have been developed to help prevent COVID-19 infection. Similar to other vaccines, common side effects including fever, fatigue, myalgias have occurred; however, episodes of more serious side effects have been noted. One such potentially serious sequalae is vaccine-induced thrombocytopenia (VITT), an autoimmune-mediated phenomenon hypothesized to occur due to molecular mimicry and the production of platelet PF4 antibodies, ultimately leading to thrombocytopenia and easy bruising. In this report, we present the case of a 34-year-old, otherwise, healthy female who presented with easy bruising and thrombocytopenia following completion of the two-dose Moderna COVID-19 vaccine, suspicious for a diagnosis of VITT. The patient was managed conservatively with steroids. Steroids and intravenous immune globulin therapy have been reported in the literature. This report highlights that VITT should be considered in the differential diagnosis for patient presenting with increased bruising in the setting of recent COVID-19 vaccine administration, and furthermore highlights the diagnostic workup and management options for such patients.

Regulation of pulmonary inflammation and fibrosis through expression of integrins alphaVbeta3 and alphaVbeta5 on pulmonary T lymphocytes.

OBJECTIVE: Pulmonary diseases associated with fibrosis, including scleroderma lung disease, are characterized by the accumulation of T cells in the lungs. These cells are thought to facilitate lung fibrosis, but the exact mechanisms of their profibrotic action are not clear. Several alphaV-containing integrins, including alphaVbeta3 and alphaVbeta5, have been shown to directly activate transforming growth factor beta (TGFbeta) and promote collagen accumulation. The aim of this study was to investigate whether pulmonary T cells express profibrotic integrins and regulate collagen accumulation. METHODS: Expression of integrins was assessed by immunohistochemical analysis of lung tissue, by flow cytometry using bronchoalveolar lavage fluid from patients with systemic sclerosis (SSc), and in a CCL18 overexpression animal model of pulmonary T cell infiltration. Experiments in cell cultures were performed to determine whether integrin-expressing T cells are profibrotic in cocultures with pulmonary fibroblasts and, if so, through what possible mechanism. RESULTS: Lymphocytes and integrin-positive cells were present in the lungs, and pulmonary T cells expressed integrins alphaVbeta3 and alphaVbeta5 in patients with SSc and in the animal model. Systemic administration of neutralizing anti-integrin alphaV antibody or a genetic deficiency of integrin beta3 in the CCL18 overexpression model significantly attenuated CCL18-driven pulmonary lymphocytic infiltration and collagen accumulation. Jurkat T cells overexpressing integrin alphaVbeta3 or integrin alphaVbeta5 in cocultures with primary pulmonary fibroblasts stimulated collagen accumulation and Smad2 nuclear translocation. Neutralizing anti-TGFbeta antibody attenuated the profibrotic effect of integrin-expressing T cells. CONCLUSION: Pulmonary infiltrating T lymphocytes may express integrins alphaVbeta3 and alphaVbeta5 that are necessary for lymphocytic infiltration and T cell-associated TGFbeta activation and collagen accumulation.

Macrophages produce TGF-beta-induced (beta-ig-h3) following ingestion of apoptotic cells and regulate MMP14 levels and collagen turnover in fibroblasts.

Phagocytic clearance of apoptotic cells by macrophages is an essential part in the resolution of inflammation. It coincides with activation of repair mechanisms, including accumulation of extracellular matrix. A possible link between clearance of apoptotic debris and accumulation of extracellular matrix has not been investigated. Production of collagen was measured in primary fibroblasts cocultured with macrophages. Ingestion of apoptotic cells by monocyte-derived macrophages led to up-regulation of collagen. Direct contact between macrophages and fibroblasts was not required for collagen up-regulation. Macrophages produced TGF-beta following ingestion of apoptotic cells, but the levels of this cytokine were lower than those required for a significant up-regulation of collagen. Simultaneously, the levels of TGF-beta-induced (TGFBI), or keratoepithelin/BIGH3, mRNA and protein were increased. In contrast, primary alveolar macrophages stimulated collagen production without exposure to apoptotic cells; there was no further increase in the levels of TGFBI, mRNA or protein, or collagen after ingestion of apoptotic cells. Stimulation of fibroblasts with TGFBI down-regulated MMP14 levels, decreased DNA binding by p53, increased DNA binding by PU.1, and up-regulated collagen protein but not mRNA levels. Overexpression of MMP14 or p53, or small interfering RNA-mediated inhibition of PU.1 led to an increase in MMP14 and a decline in collagen levels, whereas small interfering RNA-mediated inhibition of MMP14 led to elevation of collagen levels. In conclusion, monocyte-derived but not alveolar macrophages produce TGFBI following ingestion of apoptotic cells, leading to the down-regulation of MMP14 levels in fibroblasts through a mechanism involving p53 and PU.1, and to subsequent accumulation of collagen.

PKCalpha mediates CCL18-stimulated collagen production in pulmonary fibroblasts.

A CC chemokine, CCL18, has been previously reported to stimulate collagen production in pulmonary fibroblasts. This study focused on the role of protein kinase C (PKC) in the profibrotic signaling activated by CCL18 in pulmonary fibroblasts. Of the three PKC isoforms that are predominantly expressed in fibroblasts (PKCalpha, PKCdelta, and PKCepsilon), two isoforms (PKCdelta and PKCepsilon) have been implicated in profibrotic intracellular signaling. The role of PKCalpha-mediated signaling in the regulation of collagen production remains unclear. In this study, PKCalpha was found mostly in the cytoplasm, whereas PKCdelta and PKCepsilon were found mostly in the nucleus of cultured primary pulmonary fibroblasts. In response to stimulation with CCL18, PKCalpha but not PKCdelta or PKCepsilon underwent rapid (within 5-10 min) transient phosphorylation and nuclear translocation. Inhibition with dominant-negative mutants of PKCalpha and ERK2, but not PKCdelta or PKCepsilon, abrogated CCL18-stimulated ERK2 phosphorylation and collagen production. The effect of CCL18 on collagen production and the activity of collagen promoter reporter constructs were also abrogated by a selective pharmacologic inhibitor of PKCalpha Gö6976. Stimulation of fibroblasts with CCL18 caused an increase in intracellular calcium concentration. Consistent with the known calcium dependence of PKCalpha signaling, blocking of the calcium signaling with the intracellular calcium-chelating agent BAPTA led to abrogation of PKCalpha nuclear translocation, ERK2 phosphorylation, and collagen production. These observations suggest that in primary pulmonary fibroblasts, PKCalpha but not PKCdelta or PKCepsilon mediate the profibrotic effect of CCL18. PKCalpha may therefore become a viable target for future antifibrotic therapies.