Impacts of climate variability on tree demography in second growth tropical forests: the importance of regional context for predicting successional trajectories

Naturally regenerating and restored second growth forests account for over 70% of tropical forest cover and provide key ecosystem services. Understanding climate change impacts on successional trajectories of these ecosystems is critical for developing effective large‐scale forest landscape restoration (FLR) programs. Differences in environmental conditions, species composition, dynamics, and landscape context from old growth forests may exacerbate climate impacts on second growth stands. We compile data from 112 studies on the effects of natural climate variability, including warming, droughts, fires, and cyclonic storms, on demography and dynamics of second growth forest trees and identify variation in forest responses across biomes, regions, and landscapes. Across studies, drought decreases tree growth, survival, and recruitment, particularly during early succession, but the effects of temperature remain unexplored. Shifts in the frequency and severity of disturbance alter successional trajectories and increase the extent of second growth forests. Vulnerability to climate extremes is generally inversely related to long‐term exposure, which varies with historical climate and biogeography. The majority of studies, however, have been conducted in the Neotropics hindering generalization. Effects of fire and cyclonic storms often lead to positive feedbacks, increasing vulnerability to climate extremes and subsequent disturbance. Fragmentation increases forests’ vulnerability to fires, wind, and drought, while land use and other human activities influence the frequency and intensity of fire, potentially retarding succession. Comparative studies of climate effects on tropical forest succession across biogeographic regions are required to forecast the response of tropical forest landscapes to future climates and to implement effective FLR policies and programs in these landscapes.     

Some observations on the effect of Daflon (micronized purified flavonoid fraction of Rutaceae aurantiae) in bancroftian filarial lymphoedema

BACKGROUND: Morbidity management is a core component of the global programme for the elimination of lymphatic filariasis. In a double-blind clinical trial, the tolerability and efficacy of Daflon (500 mg) + DEC (25 mg) or DEC (25 mg) alone, twice daily for 90 days, was studied in 26 patients with bancroftian filarial lymphoedema. RESULTS: None of the patients in either drug group reported any adverse reaction throughout the treatment period (90 days). Haematological and biochemical parameters were within normal limits and there was no significant difference between the pre-treatment (day 0) and post-treatment (day 90) values. The group receiving Daflon showed significant reduction in oedema volume from day 90 (140.6 PlusMinus; 18.8 ml) to day 360 (71.8 PlusMinus; 20.7 ml) compared to the pre-treatment (day 0, 198.4 PlusMinus; 16.5 ml) value. This accounted for a 63.8% reduction in oedema volume by day 360 (considering the pre-treatment (day 0) as 100%). In the DEC group, the changes in oedema volume (between day 1 and day 360) were not significant when compared to the pre-treatment (day 0) value. The percentage reduction at day 360 was only 9%, which was not significant (P > 0.05). CONCLUSION: This study has shown that Daflon (500 mg, twice a day for 90 days) is both safe and efficacious in reducing oedema volume in bancroftian filarial lymphoedema. Further clinical trials are essential for strengthening the evidence base on the role of this drug in the morbidity management of lymphatic filariasis.     

Direct intracardiac injection of umbilical cord-derived stromal cells and umbilical cord blood-derived endothelial cells for the treatment of ischemic cardiomyopathy

The development of new therapeutic strategies is necessary to reduce the worldwide social and economic impact of cardiovascular disease, which produces high rates of morbidity and mortality. A therapeutic option that has emerged in the last decade is cell therapy. The aim of this study was to compare the effect of transplanting human umbilical cord-derived stromal cells (UCSCs), human umbilical cord blood-derived endothelial cells (UCBECs) or a combination of these two cell types for the treatment of ischemic cardiomyopathy (IC) in a Wistar rat model. IC was induced by left coronary artery ligation, and baseline echocardiography was performed seven days later. Animals with a left ventricular ejection fraction (LVEF) of ≤40% were selected for the study. On the ninth day after IC was induced, the animals were randomized into the following experimental groups: UCSCs, UCBECs, UCSCs plus UCBECs, or vehicle (control). Thirty days after treatment, an echocardiographic analysis was performed, followed by euthanasia. The animals in all of the cell therapy groups, regardless of the cell type transplanted, had less collagen deposition in their heart tissue and demonstrated a significant improvement in myocardial function after IC. Furthermore, there was a trend of increasing numbers of blood vessels in the infarcted area. The median value of LVEF increased by 7.19% to 11.77%, whereas the control group decreased by 0.24%. These results suggest that UCSCs and UCBECs are promising cells for cellular cardiomyoplasty and can be an effective therapy for improving cardiac function following IC.     

The bactericidal effect of ultraviolet and visible light on Escherichia coli

The bactericidal radiation dosages at specific wavelengths in the ultraviolet (UV)-visible spectrum are not well documented. Such information is important for the development of new monochromatic bactericidal devices to be operated at different wavelengths. In this study, radiation dosages required to cause mortality of an Escherichia coli strain, ATCC 25922, at various wavelengths between 250 and 532 nm in the UV and visible spectrum were determined. Radiation at 265 nm in the UV region was most efficient in killing the E. coli cells and 100% mortality was achieved at a dose of 1.17 log mJ/cm(2). In the visible spectrum, the radiation dosages required for a one-log reduction of the E. coli cell density at 458 and 488 nm were 5.5 and 6.9 log mJ/cm(2), respectively. However, at 515 and 532 nm, significant killing was not observed at radiation dosage up to 7 log mJ/cm(2). Based on the cell survival data at various radiation dosages between 250 and 488 nm, a predictive equation for the survival of E. coli cells is derived, namely log(S/S(0)) = -(1.089 x 10(7) e(-0.0633lambda))D. The symbols, S(0), S, lambda, and D, represent initial cell density, cell density after irradiation, wavelength of the radiation and radiation dosage, respectively. The proportion of the surviving E. coli cells decreases exponentially with the increase in radiation dosage at a given wavelength. In addition, the radiation dose required for killing a certain fraction of the E. coli cells increases exponentially as the wavelength of radiation increases.     

RIG-I mediates the co-induction of tumor necrosis factor and type I interferon elicited by myxoma virus in primary human macrophages

The sensing of pathogen infection and subsequent triggering of innate immunity are key to controlling zoonotic infections. Myxoma virus (MV) is a cytoplasmic DNA poxvirus that in nature infects only rabbits. Our previous studies have shown that MV infection of primary mouse cells is restricted by virus-induced type I interferon (IFN). However, little is known about the innate sensor(s) involved in activating signaling pathways leading to cellular defense responses in primary human immune cells. Here, we show that the complete restriction of MV infection in the primary human fibroblasts requires both tumor necrosis factor (TNF) and type I IFN. We also demonstrate that MV infection of primary human macrophages (pHMs) activates the cytoplasmic RNA sensor called retinoic acid inducible gene I (RIG-I), which coordinately induces the production of both TNF and type I IFN. Of note, RIG-I sensing of MV infection in pHMs initiates a sustained TNF induction through the sequential involvement of the downstream IFN-regulatory factors 3 and 7 (IRF3 and IRF7). Thus, RIG-I-mediated co-induction of TNF and type I IFN by virus-infected pHMs represents a novel innate defense mechanism to restrict viral infection in human cells. These results also reveal a new regulatory mechanism for TNF induction following viral infection.     

The Myxoma Virus M-T5 Ankyrin Repeat Host Range Protein Is a Novel Adaptor That Coordinately Links the Cellular Signaling Pathways Mediated by Akt and Skp1 in Virus-Infected Cells

Most poxviruses express multiple proteins containing ankyrin (ANK) repeats accounting for a large superfamily of related but unique determinants of poxviral tropism. Recently, select members of this novel family of poxvirus proteins have drawn considerable attention for their potential roles in modulating intracellular signaling networks during viral infection. The rabbit-specific poxvirus, myxoma virus (MYXV), encodes four unique ANK repeat proteins, termed M-T5, M148, M149, and M150, all of which include a carboxy-terminal PRANC domain which closely resembles a cellular protein motif called the F-box domain. Here, we show that each MYXV-encoded ANK repeat protein, including M-T5, interacts directly with the Skp1 component of the host SCF ubiquitin ligase complex, and that the binding of M-T5 to cullin 1 is indirect via binding to Skp1 in the host SCF complex. To understand the significance of these virus-host protein interactions, the various binding domains of M-T5 were mapped. The N-terminal ANK repeats I and II were identified as being important for interaction with Akt, whereas the C-terminal PRANC/F-box-like domain was essential for binding to Skp1. We also report that M-T5 can bind Akt and the host SCF complex (via Skp1) simultaneously in MYXV-infected cells. Finally, we report that M-T5 specifically mediates the relocalization of Akt from the nucleus to the cytoplasm during infection with the wild-type MYXV, but not the M-T5 knockout version of the virus. These results indicate that ANK/PRANC proteins play a critical role in reprogramming disparate cellular signaling cascades to establish a new cellular environment more favorable for virus replication.Myxoma virus (MYXV) is a rabbit-specific poxvirus that has proven to be a useful model system to study the mechanism by which virus-encoded immunoregulatory proteins function to manipulate the various host immune responses during the course of viral infection (50). In its long-term evolutionary host (Sylvilagus sp.), MYXV causes a benign disease localized to the site of inoculation, but when the virus infects European rabbits (Oryctolagus cuniculus), it causes a rapid systemic and highly lethal infection called myxomatosis (13). The success of MYXV as a pathogen can be attributed to the ability of the virus to effectively avoid recognition and clearance by the immune systems of susceptible rabbit hosts. At the level of individual virus-infected cells, poxviruses, like MYXV, are particularly adept at binding and entering most mammalian cells, where they attempt to establish a favorable intracellular environment, which promotes viral replication. Thus, the ability of poxviruses to reconfigure or disable the various host antiviral responses of the infected cell directly dictates the outcome of a viral infection at the cellular level (28). To this end, poxviruses possess a large genomic capacity, and all encode a unique repertoire of immunoregulatory and host-interactive proteins that have evolved to specifically mediate a broad range of cellular processes critical for successful viral replication. To date, a large collection of poxvirus-encoded immunoregulatory proteins have been identified and characterized, including virokines, viroreceptors, signaling modulators, and inhibitors of various antiviral responses, such as apoptotic pathways and interferon signaling (43). More recently, a novel category of poxvirus ankyrin (ANK) repeat proteins have drawn considerable attention for their potential roles in modulating intracellular signaling networks during viral infection (48, 49, 53).With the exception of poxviruses, the ANK motif is not commonly reported in viruses, although numerous examples have been identified in eukaryotic, bacterial, and archaeal proteins (6). The ANK motif, a tandemly repeated consensus module of approximately 33 amino acid residues, has been demonstrated to mediate diverse protein-protein interactions between cellular proteins having a broad spectrum of functional roles (32, 42). Solved crystal structures have revealed a conserved fold structure of the ANK repeat unit, by which each repeat forms a characteristic helix-loop-helix structure with a beta-hairpin/loop region projecting out from the helices at a 90° angle (3, 16, 19, 26). However, the ANK fold appears to be defined by its structure rather than any conserved biological function since there is no specific conserved substrate or binding partner structure that is universally recognized by members of the superfamily.The majority of poxviral ANK repeat-containing proteins also include a conserved carboxy-terminal PRANC (pox protein repeats of ankyrin C terminus) motif, which closely resembles a cellular protein motif called the F-box domain (30). Characterized as substrate adaptors, F-box-containing host proteins function to recruit cellular substrate proteins to the SCF ubiquitin-ligase complex (named after their main components, Skp1, cullin 1 [CUL1], and an F-box protein), where the substrates selected by the complex are ubiquitinated and targeted for degradation by the proteasome (21, 45, 60). The process of selective ubiquitination is an essential regulatory step for many cellular processes, and the human genome encodes more than 70 different F-box proteins, which collectively are thought to specifically target a broad collection of cellular substrates for delivery to the SCF complex to initiate turnover (62).Accounting for the largest family of poxviral proteins, almost all chordopoxviruses encode multiple ANK repeat-containing proteins, some of which have been defined as viral host range or virulence factors (30). For example, canarypox virus encodes 51 ANK repeat proteins, accounting for greater than 20% of the genome; however, most other poxviruses express less than a half dozen ANK repeat proteins (52). MYXV encodes four unique ANK repeat proteins, termed M-T5, M148, M149, and M150, all of which have been described as virulence factors for myxomatosis in rabbits (5, 8, 33). The MYXV host range factor M-T5 was first characterized for its ability to regulate viral tropism within rabbit lymphocytes and, later, some classes of human cancer cell lines (33, 51). In human cancer cells, the direct physical interaction between M-T5 and the host cell Akt was shown to be a key restriction determinant for MYXV tropism in a subset referred to as type II cancer cells (56). Furthermore, M-T5 was shown to be functionally interchangeable with a host ANK repeat protein called PIKE-A, and the activation of Akt by either the viral M-T5 or the host PIKE-A protein was critical for MYXV permissiveness in type II human cancer cells (57). M-T5 was also demonstrated to protect MYXV-infected cells from virus-induced cell cycle arrest, a property which was linked to its ability to interact with a member of the host cell SCF complex called CUL1 (20). Unlike M-T5, no specific host binding partners or target substrates have yet been identified for M148, M149, or M150. However, in tumor necrosis factor alpha (TNF-α)-stimulated cells, M150 was shown to colocalize in the nucleus with NF-κB p65, suggesting that this MYXV protein may modulate the NF-κB pathway (8).In this study, we demonstrate that M-T5, M148, M149, and M150 all have functional carboxy-terminal PRANC/F-box-like domains and that each one can interact directly with the Skp1 component of the host SCF complex. We further examined the various binding domains of M-T5 and identified ANK repeats I and II as being important for interaction with Akt, whereas the PRANC/F-box-like domain was essential for binding to Skp1. We also show that the previously reported interaction of M-T5 with CUL1 was in fact, indirect linking of M-T5 to the host SCF complex via Skp1. More specifically, we investigated the ability of M-T5 to function as a molecular scaffold to link disparate cellular binding partners together within a single complex and report that the viral protein binds Akt and the SCF complex (via Skp1) simultaneously in MYXV-infected cells. Finally, we demonstrate that M-T5 specifically mediates the relocalization of Akt from the nucleus to the cytoplasm during MYXV infection. These results suggest that ANK/PRANC proteins, such as M-T5, play a critical role in reprogramming disparate cellular signaling cascades to establish a new cellular environment more favorable for viral replication.     

Pharmacological Manipulation of the Akt Signaling Pathway Regulates Myxoma Virus Replication and Tropism in Human Cancer Cells

Viruses have evolved an assortment of mechanisms for regulating the Akt signaling pathway to establish a cellular environment more favorable for viral replication. Myxoma virus (MYXV) is a rabbit-specific poxvirus that encodes many immunomodulatory factors, including an ankyrin repeat-containing host range protein termed M-T5 that functions to regulate tropism of MYXV for rabbit lymphocytes and certain human cancer cells. MYXV permissiveness in these human cancer cells is dependent upon the direct interaction between M-T5 and Akt, which has been shown to induce the kinase activity of Akt. In this study, an array of compounds that selectively manipulate Akt signaling was screened and we show that only a subset of Akt inhibitors significantly decreased the ability of MYXV to replicate in previously permissive human cancer cells. Furthermore, reduced viral replication efficiency was correlated with lower levels of phosphorylated Akt. In contrast, the PP2A-specific phosphatase inhibitor okadaic acid promoted increased Akt kinase activation and rescued MYXV replication in human cancer cells that did not previously support viral replication. Finally, phosphorylation of Akt at residue Thr308 was shown to dictate the physical interaction between Akt and M-T5, which then leads to phosphorylation of Ser473 and permits productive MYXV replication in these human cancer cells. The results of this study further characterize the mechanism by which M-T5 exploits the Akt signaling cascade and affirms this interaction as a major tropism determinant that regulates the replication efficiency of MYXV in human cancer cells.Following viral infection, substantial alterations in cellular physiology often lead to modification of various cellular pathways critical to the success of viral replication. The demands for energy, nutrients, and macromolecular synthesis that accompany viral replication can be substantial; thus, many viruses have evolved elaborate strategies for hijacking key cellular signaling networks necessary to support their demands (9). By the same token, antiviral pathways activated by the virus infection may also need to be blocked or subverted to ensure successful virus replication. Poxviruses possess large double-stranded DNA (dsDNA) genomes that encode multiple gene products that specifically modify or debilitate the various host signaling responses of the infected cell (28). Many of the immunoregulatory factors expressed by poxviruses have been well characterized, and these factors include virokines, viroreceptors, signaling modulators, and inhibitors of various antiviral responses, such as initiation of apoptosis pathways and signaling by protective cytokines, like interferon and tumor necrosis factor (TNF) (42).Myxoma virus (MYXV) is a member of the Leporipoxvirus genus and exhibits a restricted pathogenesis that is limited to rabbits, primarily due to its specific immunomodulation of the immune system of leporids (48). In rabbits (Sylvilagus spp.) of the Americas, MYXV infection results in a benign infection, characterized by a cutaneous fibroma restricted to the site of inoculation (14); however, the same virus causes a rapid systemic and highly lethal infection called myxomatosis in European rabbits (Oryctolagus cuniculus) (15). Although MYXV has a narrow host range in nature and is pathogenic only to European rabbits, the tropism of MYXV has recently been extended to include human tumor cells in vitro (6, 47, 54, 57, 60) and in xenografted mice in vivo (24, 25, 61). The mechanisms that mediate MYXV tropism in human cancer cells are still being investigated, but one signaling requirement has been linked to the state of cellular Akt kinase activity (57). Human cancer cells (called type I) that exhibit high levels of endogenous phosphorylated Akt (Ser473 and Thr308) supported permissive MYXV replication, while cells with no detectable endogenous phosphorylated Akt, which were unaffected by the virus infection, were nonpermissive (type III). A unique subset of cancer cells (type II) were found to be permissive to wild-type MYXV but did not support MYXV replication following the deletion of the viral host range factor M-T5 (vMyxT5KO). These type II cells constitutively expressed only low levels of endogenous phosphorylated Akt (mostly at Thr308), but following infection with permissive MYXV, a significant increase in Akt phosphorylation (particularly at Ser473) was observed. In stark contrast, the endogenous levels of phosphorylated Akt remained essentially unchanged when type II cells were infected with the nonpermissive M-T5 knockout virus MYXV (vMyxT5KO) (57).The host range factor M-T5 is essential for MYXV replication in rabbit primary lymphocytes (RL-5 cells) and for virus pathogenesis in European rabbits (31). Structurally, M-T5 possesses seven ankyrin (ANK) repeats and a carboxyl-terminal PRANC (pox protein repeats of ankyrin C-terminal) motif, which closely resembles a cellular protein motif called the F-box domain (29). Interaction between M-T5 and components of the cellular SCF (Skp-cullin-F-box) ubiquitin ligase complex was shown to protect MYXV-infected cells from cell cycle arrest (19). In MYXV-infected type II human cancer cells, physical interaction between M-T5 and cellular Akt was shown to upregulate the kinase activity of Akt (57). In another study, M-T5 was shown to be functionally interchangeable with the host ANK repeat-containing protein PIKE-A, and activation of Akt by either PIKE-A or the viral M-T5 protein was sufficient to mediate MYXV permissiveness in type II human cancer cells (59). Similarly, addition of the immunosuppressant drug rapamycin was successful at rescuing vMyxT5KO replication in type II cells by upregulating Akt activation through the mTOR pathway (47). The critical role of Akt in the regulation of multiple biological processes makes Akt a central regulator of cellular signaling, and therefore, it is not surprising that many viruses have developed sophisticated strategies for manipulating the activation of Akt (9, 11).The serine/threonine kinase Akt (also called protein kinase B [PKB]) was initially discovered as the cellular homolog of the viral oncogene (v-Akt) carried by the AKT8 retrovirus isolated from a murine T-cell lymphoma (7, 20, 46). There are three isoforms found in mammals (Akt1, -2, and -3), encoded by separate genes but sharing over 80% amino acid sequence identity. Activation of Akt is predominantly dependent upon phosphoinositide 3-kinase (PI3K), which phosphorylates phosphoinositides (PIs) at the D3 position of the inositol ring to generate PI(3,4,5)P₃ (PIP₃). Akt possesses an N-terminal PH (pleckstrin homology) domain that binds PIP₃ to promote its translocation of the plasma membrane. Once localized at the membrane, Akt becomes phosphorylated at residue Thr308 in the activation loop by phosphoinositide-dependent kinase 1 (PDK1) and also within the carboxy terminus at residue Ser473 by mTORC2 (mammalian target of rapamycin complex 2) (2, 49, 50). Phosphorylation of both sites is necessary for full induction of Akt kinase activity. Akt is a key regulator of many important cellular functions, including cell survival, proliferation, glucose metabolism, and protein synthesis. In the majority of human cancer cells, the Akt pathway is either mutated or constitutively activated, contributing to cancer progression through both stimulation of cellular proliferation and inhibition of apoptosis (34, 55).In this study, we screened an array of Akt inhibitor compounds that selectively manipulate the Akt signaling network at some level and report that certain Akt inhibitors significantly blocked MYXV replication in previously permissive type I and II human cancer cells. An additional set of inhibitors selectively inhibited only the replication of MYXV deleted for M-T5 and did not modify the replicative ability of the parental wild-type virus. Furthermore, the decrease in viral replication efficiency was correlated with lower levels of phosphorylated Akt at residues Thr308 and Ser473. In contrast, certain PP2A-specific phosphatase inhibitors, such as okadaic acid, promoted increased Akt kinase activation and rescued MYXV replication in type III human cancer cells that did not previously support viral replication. Finally, we demonstrate that the hemi-phosphorylation of Akt at residue Thr308 dictates physical interaction between Akt and M-T5, which ultimately leads to productive MYXV replication in type II cancer cells. These studies show that activation of the Akt signaling cascade is essential for efficient MYXV replication in human cancer cells and further demonstrate the dynamic role by which M-T5 manipulates Akt signaling to establish a cellular environment more favorable for viral replication.     

Airway hyperresponsiveness is associated with airway remodeling but not inflammation in aging Cav1-/- mice

Background

Airway inflammation and airway remodeling are the key contributors to airway hyperresponsiveness (AHR), a characteristic feature of asthma. Both processes are regulated by Transforming Growth Factor (TGF)-β. Caveolin 1 (Cav1) is a membrane bound protein that binds to a variety of receptor and signaling proteins, including the TGF-β receptors. We hypothesized that caveolin-1 deficiency promotes structural alterations of the airways that develop with age will predispose to an increased response to allergen challenge.

Methods

AHR was measured in Cav1-deficient and wild-type (WT) mice 1 to 12 months of age to examine the role of Cav1 in AHR and the relative contribution of inflammation and airway remodeling. AHR was then measured in Cav1^-/- and WT mice after an ovalbumin-allergen challenge performed at either 2 months of age, when remodeling in Cav1^-/- and WT mice was equivalent, and at 6 months of age, when the Cav1^-/- mice had established airway remodeling.

Results

Cav1^-/- mice developed increased thickness of the subepithelial layer and a correspondingly increased AHR as they aged. In addition, allergen-challenged Cav1^-/- mice had an increase in AHR greater than WT mice that was largely independent of inflammation. Cav1^-/- mice challenged at 6 months of age have decreased AHR compared to those challenged at 2 months with correspondingly decreased BAL IL-4 and IL-5 levels, inflammatory cell counts and percentage of eosinophils. In addition, in response to OVA challenge, the number of goblet cells and α-SMA positive cells in the airways were reduced with age in response to OVA challenge in contrast to an increased collagen deposition further enhanced in absence of Cav1.

Conclusion

A lack of Cav1 contributed to the thickness of the subepithelial layer in mice as they aged resulting in an increase in AHR independent of inflammation, demonstrating the important contribution of airway structural changes to AHR. In addition, age in the Cav1^-/- mice is a contributing factor to airway remodeling in the response to allergen challenge.