Systemic HIV and SIV latency reversal via non-canonical NF-κB signalling in vivo.

Long-lasting, latently infected resting CD4+ T cells are the greatest obstacle to obtaining a cure for HIV infection, as these cells can persist despite decades of treatment with antiretroviral therapy (ART). Estimates indicate that more than 70 years of continuous, fully suppressive ART are needed to eliminate the HIV reservoir1. Alternatively, induction of HIV from its latent state could accelerate the decrease in the reservoir, thus reducing the time to eradication. Previous attempts to reactivate latent HIV in preclinical animal models and in clinical trials have measured HIV induction in the peripheral blood with minimal focus on tissue reservoirs and have had limited effect2-9. Here we show that activation of the non-canonical NF-κB signalling pathway by AZD5582 results in the induction of HIV and SIV RNA expression in the blood and tissues of ART-suppressed bone-marrow-liver-thymus (BLT) humanized mice and rhesus macaques infected with HIV and SIV, respectively. Analysis of resting CD4+ T cells from tissues after AZD5582 treatment revealed increased SIV RNA expression in the lymph nodes of macaques and robust induction of HIV in almost all tissues analysed in humanized mice, including the lymph nodes, thymus, bone marrow, liver and lung. This promising approach to latency reversal-in combination with appropriate tools for systemic clearance of persistent HIV infection-greatly increases opportunities for HIV eradication.

Precision mouse models with expanded tropism for human pathogens.

A major limitation of current humanized mouse models is that they primarily enable the analysis of human-specific pathogens that infect hematopoietic cells. However, most human pathogens target other cell types, including epithelial, endothelial and mesenchymal cells. Here, we show that implantation of human lung tissue, which contains up to 40 cell types, including nonhematopoietic cells, into immunodeficient mice (lung-only mice) resulted in the development of a highly vascularized lung implant. We demonstrate that emerging and clinically relevant human pathogens such as Middle East respiratory syndrome coronavirus, Zika virus, respiratory syncytial virus and cytomegalovirus replicate in vivo in these lung implants. When incorporated into bone marrow/liver/thymus humanized mice, lung implants are repopulated with autologous human hematopoietic cells. We show robust antigen-specific humoral and T-cell responses following cytomegalovirus infection that control virus replication. Lung-only mice and bone marrow/liver/thymus-lung humanized mice substantially increase the number of human pathogens that can be studied in vivo, facilitating the in vivo testing of therapeutics.

T cells establish and maintain CNS viral infection in HIV-infected humanized mice.

The human brain is an important site of HIV replication and persistence during antiretroviral therapy (ART). Direct evaluation of HIV infection in the brains of otherwise healthy individuals is not feasible; therefore, we performed a large-scale study of bone marrow/liver/thymus (BLT) humanized mice as an in vivo model to study HIV infection in the brain. Human immune cells, including CD4+ T cells and macrophages, were present throughout the BLT mouse brain. HIV DNA, HIV RNA, and/or p24+ cells were observed in the brains of HIV-infected animals, regardless of the HIV isolate used. HIV infection resulted in decreased numbers of CD4+ T cells, increased numbers of CD8+ T cells, and a decreased CD4+/CD8+ T cell ratio in the brain. Using humanized T cell-only mice (ToM), we demonstrated that T cells establish and maintain HIV infection of the brain in the complete absence of human myeloid cells. HIV infection of ToM resulted in CD4+ T cell depletion and a reduced CD4+/CD8+ T cell ratio. ART significantly reduced HIV levels in the BLT mouse brain, and the immune cell populations present were indistinguishable from those of uninfected controls, which demonstrated the effectiveness of ART in controlling HIV replication in the CNS and returning cellular homeostasis to a pre-HIV state.

HIV persistence in tissue macrophages of humanized myeloid-only mice during antiretroviral therapy.

Despite years of fully suppressive antiretroviral therapy (ART), HIV persists in its hosts and is never eradicated. One major barrier to eradication is that the virus infects multiple cell types that may individually contribute to HIV persistence. Tissue macrophages are critical contributors to HIV pathogenesis; however, their specific role in HIV persistence during long-term suppressive ART has not been established. Using humanized myeloid-only mice (MoM), we demonstrate that HIV infection of tissue macrophages is rapidly suppressed by ART, as reflected by a rapid drop in plasma viral load and a dramatic decrease in the levels of cell-associated viral RNA and DNA. No viral rebound was observed in the plasma of 67% of the ART-treated animals at 7 weeks after ART interruption, and no replication-competent virus was rescued from the tissue macrophages obtained from these animals. In contrast, in a subset of animals (∼33%), a delayed viral rebound was observed that is consistent with the establishment of persistent infection in tissue macrophages. These observations represent the first direct evidence, to our knowledge, of HIV persistence in tissue macrophages in vivo.

Recruitment of ß-catenin to N-cadherin is necessary for smooth muscle contraction.

ß-Catenin is a key component that connects transmembrane cadherin with the actin cytoskeleton at the cell-cell interface. However, the role of the ß-catenin/cadherin interaction in smooth muscle has not been well characterized. Here stimulation with acetylcholine promoted the recruitment of ß-catenin to N-cadherin in smooth muscle cells/tissues. Knockdown of ß-catenin by lentivirus-mediated shRNA attenuated smooth muscle contraction. Nevertheless, myosin light chain phosphorylation at Ser-19 and actin polymerization in response to contractile activation were not reduced by ß-catenin knockdown. In addition, the expression of the ß-catenin armadillo domain disrupted the recruitment of ß-catenin to N-cadherin. Force development, but not myosin light chain phosphorylation and actin polymerization, was reduced by the expression of the ß-catenin armadillo domain. Furthermore, actin polymerization and microtubules have been implicated in intracellular trafficking. In this study, the treatment with the inhibitor latrunculin A diminished the interaction of ß-catenin with N-cadherin in smooth muscle. In contrast, the exposure of smooth muscle to the microtubule depolymerizer nocodazole did not affect the protein-protein interaction. Together, these findings suggest that smooth muscle contraction is mediated by the recruitment of ß-catenin to N-cadherin, which may facilitate intercellular mechanotransduction. The association of ß-catenin with N-cadherin is regulated by actin polymerization during contractile activation.

Deficits in neuronal cytochrome P450 activity attenuate opioid analgesia but not opioid side effects.

Morphine-like analgesics act on µ opioid receptors in the CNS to produce highly effective pain relief, but the same class of receptors also mediates non-therapeutic side effects. The analgesic properties of morphine were recently shown to require the activity of a brain neuronal cytochrome P450 epoxygenase, but the significance of this pathway for opioid side effects is unknown. Here we show that brain P450 activity is not required for three of morphine׳s major side effects (respiratory depression, constipation, and locomotor stimulation). Following systemic or intracerebroventricular administration of morphine, transgenic mice with brain neuron - specific reductions in P450 activity showed highly attenuated analgesic responses as compared with wild-type (control) mice. However, brain P450-deficient mice showed normal morphine-induced side effects (respiratory depression, locomotor stimulation, and inhibition of intestinal motility). Pretreatment of control mice with the P450 inhibitor CC12 similarly reduced the analgesia, but not these side effects of morphine. Because activation of brain µ opioid receptors produces both opioid analgesia and opioid side effects, dissociation of the mechanisms for the therapeutic and therapy-limiting effects of opioids has important consequences for the development of analgesics with reduced side effects and/or limited addiction liability.

Histone deacetylase 8 regulates cortactin deacetylation and contraction in smooth muscle tissues.

Histone deacetylases (HDACs) are a family of enzymes that mediate nucleosomal histone deacetylation and gene expression. Some members of the HDAC family have also been implicated in nonhistone protein deacetylation, which modulates cell-cycle control, differentiation, and cell migration. However, the role of HDACs in smooth muscle contraction is largely unknown. Here, HDAC8 was localized both in the cytoplasm and the nucleus of mouse and human smooth muscle cells. Knockdown of HDAC8 by lentivirus-encoding HDAC8 shRNA inhibited force development in response to acetylcholine. Treatment of smooth muscle tissues with HDAC8 inhibitor XXIV (OSU-HDAC-44) induced relaxation of precontracted smooth muscle tissues. In addition, cortactin is an actin-regulatory protein that undergoes deacetylation during migration of NIH 3T3 cells. In this study, acetylcholine stimulation induced cortactin deacetylation in mouse and human smooth muscle tissues, as evidenced by immunoblot analysis using antibody against acetylated lysine. Knockdown of HDAC8 by RNAi or treatment with the inhibitor attenuated cortactin deacetylation and actin polymerization without affecting myosin activation. Furthermore, expression of a charge-neutralizing cortactin mutant inhibited contraction and actin dynamics during contractile activation. These results suggest a novel mechanism for the regulation of smooth muscle contraction. In response to contractile stimulation, HDAC8 may mediate cortactin deacetylation, which subsequently promotes actin filament polymerization and smooth muscle contraction.

Glia maturation factor-γ phosphorylation at Tyr-104 regulates actin dynamics and contraction in human airway smooth muscle.

Actin dynamics plays an essential role in regulating airway smooth muscle contraction. The mechanisms that regulate actin dynamics in smooth muscle are not completely understood. Glia maturation factor (GMF) is a protein that has been reported to inhibit actin nucleation and to induce actin network debranching in vitro. The role of GMF in human smooth muscle cells and tissues has not been investigated. In this study, knockdown of GMF-γ by RNA interference enhanced actin polymerization and contraction in human airway smooth muscle (HASM) cells and tissues without affecting myosin phosphorylation (another important biochemical change during contractile activation). Activation of HASM cells and tissues with acetylcholine induced dissociation of GMF-γ from Arp2 of the Arp2/3 complex. Acetylcholine stimulation also increased GMF-γ phosphorylation at Tyr-104. GMF-γ phosphorylation at this residue was mediated by c-Abl tyrosine kinase. The GMF-γ mutant Y104F (phenylalanine substitution at Tyr-104) had higher association with Arp2 in HASM cells upon contractile activation. Furthermore, expression of mutant Y104F GMF-γ attenuated actin polymerization and contraction in smooth muscle. Thus, we propose a novel mechanism for the regulation of actin dynamics and smooth muscle contraction. In unstimulated smooth muscle, GMF-γ binds to the Arp2/3 complex, which induces actin disassembly and retains lower levels of F-actin. Upon contractile stimulation, phosphorylation at Tyr-104 mediated by c-Abl tyrosine kinase leads to the dissociation of GMF-γ from Arp2/3, by which GMF-γ no longer induces actin disassembly. Reduced actin disassembly renders F-actin in higher level, which facilitates smooth muscle contraction.

The association of cortactin with profilin-1 is critical for smooth muscle contraction.

Profilin-1 (Pfn-1) is an actin-regulatory protein that has a role in modulating smooth muscle contraction. However, the mechanisms that regulate Pfn-1 in smooth muscle are not fully understood. Here, stimulation with acetylcholine induced an increase in the association of the adapter protein cortactin with Pfn-1 in smooth muscle cells/tissues. Furthermore, disruption of the protein/protein interaction by a cell-permeable peptide (CTTN-I peptide) attenuated actin polymerization and smooth muscle contraction without affecting myosin light chain phosphorylation at Ser-19. Knockdown of cortactin by lentivirus-mediated RNAi also diminished actin polymerization and smooth muscle force development. However, cortactin knockdown did not affect myosin activation. In addition, cortactin phosphorylation has been implicated in nonmuscle cell migration. In this study, acetylcholine stimulation induced cortactin phosphorylation at Tyr-421 in smooth muscle cells. Phenylalanine substitution at this position impaired cortactin/Pfn-1 interaction in response to contractile activation. c-Abl is a tyrosine kinase that is necessary for actin dynamics and contraction in smooth muscle. Here, c-Abl silencing inhibited the agonist-induced cortactin phosphorylation and the association of cortactin with Pfn-1. Finally, treatment with CTTN-I peptide reduced airway resistance and smooth muscle hyperreactivity in a murine model of asthma. These results suggest that the interaction of cortactin with Pfn-1 plays a pivotal role in regulating actin dynamics, smooth muscle contraction, and airway hyperresponsiveness in asthma. The association of cortactin with Pfn-1 is regulated by c-Abl-mediated cortactin phosphorylation.

Role of c-Abl tyrosine kinase in smooth muscle cell migration.

c-Abl is a nonreceptor protein tyrosine kinase that has a role in regulating smooth muscle cell proliferation and contraction. The role of c-Abl in smooth muscle cell migration has not been investigated. In the present study, c-Abl was found in the leading edge of smooth muscle cells. Knockdown of c-Abl by RNA interference attenuated smooth muscle cell motility as evidenced by time-lapse microscopy. Furthermore, the actin-associated proteins cortactin and profilin-1 (Pfn-1) have been implicated in cell migration. In this study, cell adhesion induced cortactin phosphorylation at Tyr-421, an indication of cortactin activation. Phospho-cortactin and Pfn-1 were also found in the cell edge. Pfn-1 directly interacted with cortactin in vitro. Silencing of c-Abl attenuated adhesion-induced cortactin phosphorylation and Pfn-1 localization in the cell edge. To assess the role of cortactin/Pfn-1 coupling, we developed a cell-permeable peptide. Treatment with the peptide inhibited the interaction of cortactin with Pfn-1 without affecting cortactin phosphorylation. Moreover, treatment with the peptide impaired the recruitment of Pfn-1 to the leading edge and cell migration. Finally, ß1-integrin was required for the recruitment of c-Abl to the cell edge. Inhibition of actin dynamics impaired the spatial distribution of c-Abl. These results suggest that ß1-integrin may recruit c-Abl to the leading cell edge, which may regulate cortactin phosphorylation in response to cell adhesion. Phosphorylated cortactin may facilitate the recruitment of Pfn-1 to the cell edge, which promotes localized actin polymerization, leading edge formation, and cell movement. Conversely, actin dynamics may strengthen the recruitment of c-Abl to the leading edge.

Role of Abl in airway hyperresponsiveness and airway remodeling.

BACKGROUND: Asthma is a chronic disease that is characterized by airway hyperresponsiveness and airway remodeling. The underlying mechanisms that mediate the pathological processes are not fully understood. Abl is a non-receptor protein tyrosine kinase that has a role in the regulation of smooth muscle contraction and smooth muscle cell proliferation in vitro. The role of Abl in airway hyperresponsiveness and airway remodeling in vivo is largely unknown. METHODS: To evaluate the role of Abl in asthma pathology, we assessed the expression of Abl in airway tissues from the ovalbumin sensitized and challenged mouse model, and human asthmatic airway smooth muscle cells. In addition, we generated conditional knockout mice in which Abl expression in smooth muscle was disrupted, and then evaluated the effects of Abl conditional knockout on airway resistance, smooth muscle mass, cell proliferation, IL-13 and CCL2 in the mouse model of asthma. Furthermore, we determined the effects of the Abl pharmacological inhibitors imatinib and GNF-5 on these processes in the animal model of asthma. RESULTS: The expression of Abl was upregulated in airway tissues of the animal model of asthma and in airway smooth muscle cells of patients with severe asthma. Conditional knockout of Abl attenuated airway resistance, smooth muscle mass and staining of proliferating cell nuclear antigen in the airway of mice sensitized and challenged with ovalbumin. Interestingly, conditional knockout of Abl did not affect the levels of IL-13 and CCL2 in bronchoalveolar lavage fluid of animals treated with ovalbumin. However, treatment with imatinib and GNF-5 inhibited the ovalbumin-induced increase in IL-13 and CCL2 as well as airway resistance and smooth muscle growth in animals. CONCLUSIONS: These results suggest that the altered expression of Abl in airway smooth muscle may play a critical role in the development of airway hyperresponsiveness and airway remodeling in asthma. Our findings support the concept that Abl may be a novel target for the development of new therapy to treat asthma.

Role of the adapter protein Abi1 in actin-associated signaling and smooth muscle contraction.

Actin filament polymerization plays a critical role in the regulation of smooth muscle contraction. However, our knowledge regarding modulation of the actin cytoskeleton in smooth muscle just begins to accumulate. In this study, stimulation with acetylcholine (ACh) induced an increase in the association of the adapter protein c-Abl interactor 1 (Abi1) with neuronal Wiskott-Aldrich syndrome protein (N-WASP) (an actin-regulatory protein) in smooth muscle cells/tissues. Furthermore, contractile stimulation activated N-WASP in live smooth muscle cells as evidenced by changes in fluorescence resonance energy transfer efficiency of an N-WASP sensor. Abi1 knockdown by lentivirus-mediated RNAi inhibited N-WASP activation, actin polymerization, and contraction in smooth muscle. However, Abi1 silencing did not affect myosin regulatory light chain phosphorylation at Ser-19 in smooth muscle. In addition, c-Abl tyrosine kinase and Crk-associated substrate (CAS) have been shown to regulate smooth muscle contraction. The interaction of Abi1 with c-Abl and CAS has not been investigated. Here, contractile activation induced formation of a multiprotein complex including c-Abl, CAS, and Abi1. Knockdown of c-Abl and CAS attenuated the activation of Abi1 during contractile activation. More importantly, Abi1 knockdown inhibited c-Abl phosphorylation at Tyr-412 and the interaction of c-Abl with CAS. These results suggest that Abi1 is an important component of the cellular process that regulates N-WASP activation, actin dynamics, and contraction in smooth muscle. Abi1 is activated by the c-Abl-CAS pathway, and Abi1 reciprocally controls the activation of its upstream regulator c-Abl.