Gene transfer of the adaptor Lnk (SH2B3) prevents porcine endothelial cell activation and apoptosis: implication for xenograft’s cytoprotection

A novel strategy of integrating network pharmacology and transcriptome reveals antiapoptotic mechanisms of Buyang Huanwu Decoction in treating intracerebral hemorrhage

ETHNOPHARMACOLOGICAL RELEVANCE

Buyang Huanwu Decoction (BYHWD), as a traditional Chinese medical prescription, has been used to treat intracerebral hemorrhage (ICH) for hundreds of years, but the antiapoptotic properties have not yet been studied.

AIM OF THE STUDY

This study aims to elucidate the antiapoptotic mechanism of BYHWD in ICH.

MATERIALS AND METHODS

The therapeutic effect of BYHWD on ICH was assessed by modified neurological severity scores (mNSS), foot fault, and histopathological staining. Then, we used a modified comprehensive strategy by integrating transcriptome and network pharmacology to reveal the underlying mechanism. TUNEL assay, qRT-PCR, and western blot were further applied to evaluate the antiapoptotic effect of BYHWD on ICH. Dual-luciferase reporter assay and plasmid transfections were implemented to validate the potential competing endogenous RNAs (ceRNA) mechanism of Sh2b3.

RESULTS

Network pharmacology analysis indicated that the regulation of the apoptotic process was the highest enriched GO term, and that MAP kinase activity, ERK1, and ERK2 cascade were strongly correlated. Transcriptome analysis screened 180 differentially expressed mRNAs, which were highly enriched in the immune system process and negative regulation of programmed cell death. By checking the literature, we found that Sh2b3 was of great importance to apoptosis by modulating MAPK cascades. TUNEL assay validated the anti-apoptotic effect of BYHWD. Moreover, BYHWD was proven to regulate the Sh2b3-mediated ERK1/2 signaling pathway in ICH mice by qRT-PCR and western blot. We further explored the lncRNA-miRNA-mRNA network underlying the therapeutic effect, among which 4933404O12Rik/miR-185-5p is the upstream regulatory mechanism of Sh2b3.

CONCLUSIONS

We explored the antiapoptotic mechanism of BYHWD in treating ICH by a novel integrated strategy, which involved the 4933404O12Rik/miR-185-5p/Sh2b3 ceRNAs axis.

MHC Class I Masking to Prevent AMR in a Porcine Kidney Transplantation Model in Alloimmunized Recipients

Presensitized patients awaiting a kidney transplant have a lower graft survival and a longer waiting time because of the limited number of potential donors and the higher risk of antibody-mediated rejection (AMR), particularly in the early posttransplant period, because of preformed donor-specific antibodies binding major histocompatibility complex (MHC) molecules expressed by the graft endothelium followed by the activation of the complement. Advances in kidney preservation techniques allow the development of ex vivo treatment of transplants. We hypothesized that masking MHC ex vivo before transplantation could help to prevent early AMR in presensitized recipients. We evaluated a strategy of MHC I masking by an antibody during ex vivo organ perfusion in a porcine model of kidney transplantation in alloimmunized recipients.

Methods

Through the in vitro calcein-release assay and flow cytometry, we evaluated the protective effect of a monoclonal anti-swine leukocyte antigen class I antibody (clone JM1E3) against alloreactive IgG complement-dependent cytotoxicity toward donor endothelial cells. Kidneys perfused ex vivo with JM1E3 during hypothermic machine perfusion were transplanted to alloimmunized recipients.

Results

In vitro incubation of endothelial cells with JM1E3 decreased alloreactive IgG cytotoxicity (mean complement-dependent cytotoxicity index [% of control condition] with 1 µg/mL 74.13% ± 35.26 [calcein assay] and 66.88% ± 33.46 [cytometry]), with high interindividual variability. After transplantation, acute AMR occurred in all recipients on day 1, with signs of complement activation (C5b-9 staining) as soon as 1 h after transplantation, despite effective JM1E3 binding on graft endothelium.

Conclusions

Despite a partial protective effect of swine leukocyte antigen I masking with JM1E3 in vitro, ex vivo perfusion of the kidney with JM1E3 before transplantation was not sufficient alone at preventing or delaying AMR in highly sensitized recipients.

Modulating T Cell Phenotype and Function to Treat Hypertension

Hypertension is the leading modifiable risk factor of worldwide morbidity and mortality because of its effects on cardiovascular and renal end-organ damage. Unfortunately, BP control is not sufficient to fully reduce the risks of hypertension, underscoring the need for novel therapies that address end-organ damage in hypertension. Over the past several decades, the link between immune activation and hypertension has been well established, but there are still no therapies for hypertension that specifically target the immune system. In this review, we describe the critical role played by T cells in hypertension and hypertensive end-organ damage and outline potential therapeutic targets to modulate T-cell phenotype and function in hypertension without causing global immunosuppression.

The lymphocyte adapter protein: A negative regulator of myocardial ischemia/reperfusion injury

Myocardial ischemia/reperfusion (I/R) injury is the major limitation for the cardioprotective action of revascularization after myocardial infarction. Lymphocyte adapter protein (Lnk), an adapter protein, has a regulatory role in multiple signaling pathways by functioning as a scaffold for different substrates. However, the involvement of Lnk in myocardial I/R injury remains to be established. In this study, increased expression of Lnk was detected upon the development of myocardial I/R injury. Mice were genetically engineered to investigate the role of Lnk in this pathological process. Upon I/R, myocardial infarction, cardiac dysfunction, inflammation and apoptosis were increased in Lnk-deficient hearts. However, cardiomyocyte-specific overexpression of Lnk protected the hearts against myocardial I/R injury. Mechanistically, we observed that the activation of Akt, but neither ERK1/2 nor STAT3, was influenced by the expression of Lnk upon myocardial I/R injury. Furthermore, the requirement of PI3K-Akt activation for the cardioprotective effect of Lnk was confirmed in rescue experiments using the PI3K inhibitor LY294002. Taken together, our data provide a potential diagnostic and therapeutic strategy for myocardial I/R injury.

Stem cells and heart disease - Brake or accelerator?

After two decades of intensive research and attempts of clinical translation, stem cell based therapies for cardiac diseases are not getting closer to clinical success. This review tries to unravel the obstacles and focuses on underlying mechanisms as the target for regenerative therapies. At present, the principal outcome in clinical therapy does not reflect experimental evidence. It seems that the scientific obstacle is a lack of integration of knowledge from tissue repair and disease mechanisms. Recent insights from clinical trials delineate mechanisms of stem cell dysfunction and gene defects in repair mechanisms as cause of atherosclerosis and heart disease. These findings require a redirection of current practice of stem cell therapy and a reset using more detailed analysis of stem cell function interfering with disease mechanisms. To accelerate scientific development the authors suggest intensifying unified computational data analysis and shared data knowledge by using open-access data platforms.

Specific disruption of Lnk in murine endothelial progenitor cells promotes dermal wound healing via enhanced vasculogenesis, activation of myofibroblasts, and suppression of inflammatory cell recruitment

BACKGROUND

Although endothelial progenitor cells (EPCs) contribute to wound repair by promoting neovascularization, the mechanism of EPC-mediated wound healing remains poorly understood due to the lack of pivotal molecular targets of dermal wound repair.

METHODS AND RESULTS

We found that genetic targeting of the Lnk gene in EPCs dramatically enhances the vasculogenic potential including cell proliferation, migration, and tubule-like formation as well as accelerates in vivo wound healing, with a reduction in fibrotic tissue and improved neovascularization via significant suppression of inflammatory cell recruitment. When injected into wound sites, Lnk ^-/- EPCs gave rise to a significant number of new vessels, with remarkably increased survival of transplanted cells and decreased recruitment of cytotoxic T cells, macrophages, and neutrophils, but caused activation of fibroblasts in the wound-remodeling phase. Notably, in a mouse model of type I diabetes, transplanted Lnk ^-/- EPCs induced significantly better wound healing than Lnk ^+/+ EPCs did.

CONCLUSIONS

The specific targeting of Lnk may be a promising EPC-based therapeutic strategy for dermal wound healing via improvement of neovascularization but inhibition of excessive inflammation as well as activation of myofibroblasts during dermal tissue remodeling.

V, Blancho G. Bortezomib, C1-inhibitor and plasma exchange do not prolong the survival of multi-transgenic GalT-KO pig kidney xenografts in baboons

Galactosyl-transferase KO (GalT-KO) pigs represent a potential solution to xenograft rejection, particularly in the context of additional genetic modifications. We have performed life supporting kidney xenotransplantation into baboons utilizing GalT-KO pigs transgenic for human CD55/CD59/CD39/HT. Baboons received tacrolimus, mycophenolate mofetil, corticosteroids and recombinant human C1 inhibitor combined with cyclophosphamide or bortezomib with or without 2-3 plasma exchanges. One baboon received a control GalT-KO xenograft with the latter immunosuppression. All immunosuppressed baboons rejected the xenografts between days 9 and 15 with signs of acute humoral rejection, in contrast to untreated controls (n = 2) that lost their grafts on days 3 and 4. Immunofluorescence analyses showed deposition of IgM, C3, C5b-9 in rejected grafts, without C4d staining, indicating classical complement pathway blockade but alternate pathway activation. Moreover, rejected organs exhibited predominantly monocyte/macrophage infiltration with minimal lymphocyte representation. None of the recipients showed any signs of porcine endogenous retrovirus transmission but some showed evidence of porcine cytomegalovirus (PCMV) replication within the xenografts. Our work indicates that the addition of bortezomib and plasma exchange to the immunosuppressive regimen did not significantly prolong the survival of multi-transgenic GalT-KO renal xenografts. Non-Gal antibodies, the alternative complement pathway, innate mechanisms with monocyte activation and PCMV replication may have contributed to rejection.

hCTLA4-Ig transgene expression in keratocytes modulates rejection of corneal xenografts in a pig to non-human primate anterior lamellar keratoplasty model

BACKGROUND

Human corneal allografting is an established procedure to cure corneal blindness. However, a shortage of human donor corneas as well as compounding economic, cultural, and organizational reasons in many countries limit its widespread use. Artificial corneas as well as porcine corneal xenografts have been considered as possible alternatives. To date, all preclinical studies using de-cellularized pig corneas have shown encouraging graft survival results; however, relatively few studies have been conducted in pig to non-human primate (NHP) models, and particularly using genetically engineered donors.

METHODS

In this study, we assessed the potential benefit of using either hCTLA4-Ig transgenic or α1,3-Galactosyl Transferase (GT) Knock-Out (KO) plus transgenic hCD39/hCD55/hCD59/fucosyl-transferase pig lines in an anterior lamellar keratoplasty pig to NHP model.

RESULTS

Corneas from transgenic animals expressing hCTLA4-Ig under the transcriptional control of a neuron-specific enolase promoter showed transgene expression in corneal keratocytes of the stroma and expression was maintained after transplantation. Although a first acute rejection episode occurred in all animals during the second week post-keratoplasty, the median final rejection time was 70 days in the hCTLA4-Ig group vs. 21 days in the wild-type (WT) control group. In contrast, no benefit for corneal xenograft survival from the GTKO/transgenic pig line was found. At rejection, cell infiltration in hCTLA4Ig transgenic grafts was mainly composed of macrophages with fewer CD3+ CD4+ and CD79+ cells than in other types of grafts. Anti-donor xenoantibodies increased dramatically between days 9 and 14 post-surgery in all animals.

CONCLUSIONS

Local expression of the hCTLA4-Ig transgene dampens rejection of xenogeneic corneal grafts in this pig-to-NHP lamellar keratoplasty model. The hCTLA4-Ig transgene seems to target T-cell responses without impacting humoral responses, the control of which would presumably require additional peripheral immunosuppression.

LNK (SH2B3): paradoxical effects in ovarian cancer

LNK (SH2B3) is an adaptor protein studied extensively in normal and malignant hematopoietic cells. In these cells, it downregulates activated tyrosine kinases at the cell surface resulting in an antiproliferative effect. To date, no studies have examined activities of LNK in solid tumors. In this study, we found by in silico analysis and staining tissue arrays that the levels of LNK expression were elevated in high-grade ovarian cancer. To test the functional importance of this observation, LNK was either overexpressed or silenced in several ovarian cancer cell lines. Remarkably, overexpression of LNK rendered the cells resistant to death induced by either serum starvation or nutrient deprivation, and generated larger tumors using a murine xenograft model. In contrast, silencing of LNK decreased ovarian cancer cell growth in vitro and in vivo. Western blot studies indicated that overexpression of LNK upregulated and extended the transduction of the mitogenic signal, whereas silencing of LNK produced the opposite effects. Furthermore, forced expression of LNK reduced cell size, inhibited cell migration and markedly enhanced cell adhesion. Liquid chromatography-mass spectroscopy identified 14-3-3 as one of the LNK-binding partners. Our results suggest that in contrast to the findings in hematologic malignancies, the adaptor protein LNK acts as a positive signal transduction modulator in ovarian cancers.

Long-term IgG response to porcine Neu5Gc antigens without transmission of PERV in burn patients treated with porcine skin xenografts

Acellular materials of xenogenic origin are used worldwide as xenografts, and phase I trials of viable pig pancreatic islets are currently being performed. However, limited information is available on transmission of porcine endogenous retrovirus (PERV) after xenotransplantation and on the long-term immune response of recipients to xenoantigens. We analyzed the blood of burn patients who had received living pig-skin dressings for up to 8 wk for the presence of PERV as well as for the level and nature of their long term (maximum, 34 y) immune response against pig Ags. Although no evidence of PERV genomic material or anti-PERV Ab response was found, we observed a moderate increase in anti-αGal Abs and a high and sustained anti-non-αGal IgG response in those patients. Abs against the nonhuman sialic acid Neu5Gc constituted the anti-non-αGal response with the recognition pattern on a sialoglycan array differing from that of burn patients treated without pig skin. These data suggest that anti-Neu5Gc Abs represent a barrier for long-term acceptance of porcine xenografts. Because anti-Neu5Gc Abs can promote chronic inflammation, the long-term safety of living and acellular pig tissue implants in recipients warrants further evaluation.

The Lnk adaptor protein: a key regulator of normal and pathological hematopoiesis

The development and function of blood cells are regulated by specific growth factors/cytokines and their receptors' signaling pathways. In this way, these factors influence cell survival, proliferation and differentiation of hematopoietic cells. Central to this positive and/or negative control are the adaptor proteins. Since their identification 10 years ago, members of the Lnk adaptor protein family have proved to be important activators and/or inhibitors in the hematopoietic, immune and vascular system. In particular, the generation of animal and cellular models for the Lnk and APS proteins has helped establish the physiological role of these molecules through the identification of their specific signaling pathways and the characterization of their binding partners. Moreover, the recent identification of mutations in the LNK gene in myeloproliferative disorders, as well as the correlation of a single nucleotide polymorphism on LNK with hematological, immune and vascular diseases have suggested its involvement in the pathophysiology of these malignancies. The latter findings have thus raised the possibility of addressing Lnk signaling for the treatment of certain human diseases. This review therefore describes the pathophysiological role of this adaptor protein in hematological malignancies and the potential benefits of Lnk therapeutic targeting.

On the intersections of basic and applied research in xenotransplantation

I am very grateful to the Council and members of the International Xenotransplantation Association for this Honorary Membership. In accepting this prestigious award, I pay tribute to my mentors Antonio Oriol i Anguera, Carlos Martinez, Robert A. Good, and Hans Müller-Eberhard for their guidance and friendship as I was beginning my travels in biomedical research. I also thank the many gifted collaborators, students, and technical personnel, as well as the agencies and taxpayers, who funded our research and made our scientific contributions possible. Here I briefly mention some of these contributions, including early work on the immunobiology of the thymus, my short incursion in the immunology of Chagas disease, and what have been the dominant themes of my career: the mechanisms of complement injury, the role of complement in pathophysiology, and induction of cytoprotection in the vascular endothelium. I emphasize our contributions on the role of complement as related to understanding and overcoming xenograft injury, a work that has been personally very rewarding. Now it is exciting to see that the field of xenotransplantation research is moving forward vigorously, a time of great optimism suggesting that many potential clinical applications of xenotransplantation will come to fruition in the near future.

Protection of porcine endothelial cells against apoptosis with interleukin-4

BACKGROUND

Apoptosis is crucial for tissue development and homeostasis, and insufficient apoptosis is pivotal in cancer pathogenesis. Apoptosis may also be important in tissue injury and in this case, it is of interest to induce protection against apoptosis. In organ transplantation, apoptosis has been implicated in acute vascular rejection (AVR); in xenotransplantation, the inducers of apoptosis of relevance in AVR, such as tumor necrosis factor-α (TNF-α), also cause endothelial cell (EC) activation. We have previously shown that interleukin (IL)-4 and IL-13 induced protection in porcine ECs against activation and apoptosis triggered by TNF-α. Now we define signaling processes activated by IL-4 in porcine ECs and mechanisms required for IL-4-induced protection against apoptosis.

METHODS

Porcine aortic ECs were used as primary cultures or as virus-induced immortalized cells derived from galactosyl transferase-deficient (Gal(-/-) ) or wild-type pigs. ECs were stimulated with porcine IL-4, either extrinsically or transduced with recombinant adenovirus (adeno) IL-4, and analyzed using immunoblotting. Apoptosis was induced with TNF-α plus cycloheximide and assessed using neutral red uptake or flow cytometry. The role of various signaling proteins in IL-4-induced protection was established using pharmacologic inhibitors and siRNA downregulation of protein expression.

RESULTS

IL-4 induced similar degrees of phosphorylation of STAT6 in all 3 types of ECs, and STAT6 was phosphorylated through Jak3. IL-4 induced phosphorylation of Bad through Jak3. Stimulation of ECs with IL-4 caused protection of ECs against apoptosis with an absolute requirement of Jak3/STAT6 activation and major participation of mammalian target of rapamycin complex 2 (mTORC2), Akt, and extracellular signal-regulated kinase 1/2. IL-4 caused no increase in EC levels of protective proteins hemoxygenase-1, inhibitor of apoptosis protein, heat shock protein 70, Bcl-2, and Bcl-xL. ECs transduced with adenoIL-4 exhibited strong and durable protection from apoptosis. Gal(-/-) ECs were as susceptible to induction of protection with IL-4 as wild-type ECs.

CONCLUSIONS

IL-4 induces activation of Jak3/STAT6 and phosphorylation of Bad in porcine ECs, ultimately resulting in effective protection of the ECs from apoptosis. Delineation of downstream signals activated by IL-4 that are required for induction of protection suggests possible sites of intervention to design effective therapeutic agents. This is of interest because substances such as IL-4 have pleiotropic effects and cannot be used directly due to potential deleterious effects. Inducing resistance to apoptosis in porcine vascular endothelium may be important to facilitate xenograft survival and accommodation.

LNK (SH2B3) is a key regulator of integrin signaling in endothelial cells and targets α-parvin to control cell adhesion and migration

Focal adhesion (FA) formation and disassembly play an essential role in adherence and migration of endothelial cells. These processes are highly regulated and involve various signaling molecules that are not yet completely identified. Lnk [Src homology 2-B3 (SH2B3)] belongs to a family of SH2-containing proteins with important adaptor functions. In this study, we showed that Lnk distribution follows that of vinculin, localizing Lnk in FAs. Inhibition of Lnk by RNA interference resulted in decreased spreading, whereas sustained expression dramatically increases the number of focal and cell-matrix adhesions. We demonstrated that Lnk expression impairs FA turnover and cell migration and regulates β1-integrin-mediated signaling via Akt and GSK3β phosphorylation. Moreover, the α-parvin protein was identified as one of the molecular targets of Lnk responsible for impaired FA dynamics and cell migration. Finally, we established the ILK protein as a new molecular partner for Lnk and proposed a model in which Lnk regulates α-parvin expression through its interaction with ILK. Collectively, our results underline the adaptor Lnk as a novel and effective key regulator of integrin-mediated signaling controlling endothelial cell adhesion and migration.

The adaptor Lnk (SH2B3): an emerging regulator in vascular cells and a link between immune and inflammatory signaling

A better knowledge of the process by which inflammatory extracellular signals are relayed from the plasma membrane to specific intracellular sites is a key step to understand how inflammation develops and how it is regulated. This review focuses on Lnk (SH2B3) a member, with SH2B1 and SH2B2, of the SH2B family of adaptor proteins that influences a variety of signaling pathways mediated by Janus kinase and receptor tyrosine kinases. SH2B adaptor proteins contain conserved dimerization, pleckstrin homology, and SH2 domains. Initially described as a regulator of hematopoiesis and lymphocyte differentiation, Lnk now emerges as a key regulator in hematopoeitic and non hematopoeitic cells such as endothelial cells (EC) moderating growth factor and cytokine receptor-mediated signaling. In EC, Lnk is a negative regulator of TNF signaling that reduce proinflammatory phenotype and prevent EC from apoptosis. Lnk is a modulator in integrin signaling and actin cytoskeleton organization in both platelets and EC with an impact on cell adhesion, migration and thrombosis. In this review, we discuss some recent insights proposing Lnk as a key regulator of bone marrow-endothelial progenitor cell kinetics, including the ability to cell growth, endothelial commitment, mobilization, and recruitment for vascular regeneration. Finally, novel findings also provided evidences that mutations in Lnk gene are strongly linked to myeloproliferative disorders but also autoimmune and inflammatory syndromes where both immune and vascular cells display a role. Overall, these studies emphasize the importance of the Lnk adaptor molecule not only as prognostic marker but also as potential therapeutic target.