A Biography of Algernon Sydney Hartridge

Algernon Sydney Hartridge was one of three sons born of Charles and Mary Hartridge. Algernon set up his business at 92 Bay Street as a cotton factor and commercial merchant. Some­ time in 1855, Algernon marries Susan E. Knight of Richmond County. The Hartridges had five children and their names were Ada, Charles, Gazaway, Algernon, Jr., and an infant who was still born. During the Civil war, Algernon served as a first lieut­enant in the Confederate Army. He was responsible for many army commands that were made in the interest of the people of the city of Savannah. In the years to follow the Civil War, Algernon S. Hartridge became a member of the Chamber of Commerce and of the Board of Directors for the Oglethorpe Insurance Company (1864), the Savannah National Bank (1865-1868), the Tyler Cotton Press Company (1871), and the Central Railroad and banking Company of Georgia (1871-1876).https://digitalcommons.georgiasouthern.edu/sav-bios-lane/1231/thumbnail.jp

Legionella pneumophila strain 130b evades macrophage cell death independent of the effector SidF in the absence of flagellin

International audienceThe human pathogen Legionella pneumophila must evade host cell death signaling to enable replication in lung macrophages and to cause disease. After bacterial growth, however, L. pneumophila is thought to induce apoptosis during egress from macrophages. The bacterial effector protein, SidF, has been shown to control host cell survival and death by inhibiting pro-apoptotic BNIP3 and BCL-RAMBO signaling. Using live-cell imaging to follow the L. pneumophila-macrophage interaction, we now demonstrate that L. pneumophila evades host cell apoptosis independent of SidF. In the absence of SidF, L. pneumophila was able to replicate, cause loss of mitochondria membrane potential, kill macrophages, and establish infections in lungs of mice. Consistent with this, deletion of BNIP3 and BCL-RAMBO did not affect intracellular L. pneumophila replication, macrophage death rates, and in vivo bacterial virulence. Abrogating mitochondrial cell death by genetic deletion of the effectors of intrinsic apoptosis, BAX, and BAK, or the regulator of mitochondrial permeability transition pore formation, cyclophilin-D, did not affect bacterial growth or the initial killing of macrophages. Loss of BAX and BAK only marginally limited the ability of L. pneumophila to efficiently kill all macrophages over extended periods. L. pneumophila induced killing of macrophages was delayed in the absence of capsase-11 mediated pyroptosis. Together, our data demonstrate that L. pneumophila evades host cell death responses independently of SidF during replication and can induce pyroptosis to kill macrophages in a timely manner

Bcl11b sets pro-T cell fate by site-specific cofactor recruitment and by repressing Id2 and Zbtb16

Multipotent progenitor cells confirm their T cell–lineage identity in the CD4^–CD8^– double-negative (DN) pro-T cell DN2 stages, when expression of the essential transcription factor Bcl11b begins. In vivo and in vitro stage-specific deletions globally identified Bcl11b-controlled target genes in pro-T cells. Proteomics analysis revealed that Bcl11b associated with multiple cofactors and that its direct action was needed to recruit those cofactors to selective target sites. Regions near functionally regulated target genes showed enrichment for those sites of Bcl11b-dependent recruitment of cofactors, and deletion of individual cofactors relieved the repression of many genes normally repressed by Bcl11b. Runx1 collaborated with Bcl11b most frequently for both activation and repression. In parallel, Bcl11b indirectly regulated a subset of target genes by a gene network circuit via the transcription inhibitor Id2 (encoded by Id2) and transcription factor PLZF (encoded by Zbtb16); Id2 and Zbtb16 were directly repressed by Bcl11b, and Id2 and PLZF controlled distinct alternative programs. Thus, our study defines the molecular basis of direct and indirect Bcl11b actions that promote T cell identity and block alternative potentials

Programmed cell death in Legionella infection

Legionella ssp. are the causative agents of severe inflammatory pneumonia, known as Legionnaires’ Disease, which is fatal in up to 30 % of cases. Legionella replicate within alveolar macrophages by hijacking host cell pathways to establish a unique vacuolar niche. This includes the regulation of programmed host cell death factors, as Legionella must first prevent, and then induce, host cell death to promote bacterial growth and egress, respectively. However, the molecular mechanisms involved in toggling “off” and “on” host cell death signalling pathways remain undetermined. The major focus of the work described in this thesis was the delineation of the role that programmed host cell death pathways play in Legionella infection. To do this, a novel live-cell imaging technique was employed to visualise the intracellular life-cycle of Legionella and to monitor macrophage health in real-time. Using this method, I was able to confirm that wild-type Legionella induce a rapid form of cell death, termed pyroptosis, which is dependent on bacterial flagellin and the host protease, caspase-1. While flagellin/caspase-1-mediated pyroptosis prevents bacterial replication, I have identified that aflagellated Legionella also induce caspase-11-dependent pyroptosis. In contrast to caspase-1, caspase-11-mediated pyroptosis is induced in the late stages of infection, concomitant with Legionella egress, and does not interfere with intracellular bacterial replication. Legionella are also thought to induce other forms of host cell death, however, genetic ablation of mitochondrial apoptosis (BAX and BAK deletion), caspase-independent necroptotic cell death (RIPK3 and MLKL deletion), or BNIP3 and BCL-RAMBO, the putative targets of the effector protein SidF, did not affect Legionella replication or the killing of host macrophages. Legionella must prevent the activation of host cell death signalling to allow for efficient replication. While down-regulation of flagellin enables intracellular growth in the presence of caspase-1, little is known about how Legionella might evade apoptotic cell death. Using live-cell imaging, I have now shown that Legionella-infected macrophages depend critically upon the anti-apoptotic activity of host cell BCL-XL, but not other BCL-2 family members, for viability. In the absence of BCL-XL, Legionella-infected cells underwent apoptosis, which abolished bacterial replication and dissemination. Legionella infection could be fully restored by inhibiting mitochondrial apoptosis, either via BAX/BAK deletion or caspase inhibition. A single dose of BCL-XL-targeted BH3-mimetic therapy significantly reduced Legionella burden in the lungs of mice and prevented lethal bacterial infection. Mechanistically, I identified that Legionella infection inhibits host protein synthesis, which sensitises macrophages to BCL-XL loss or inhibition, via depletion of another anti-apoptotic BCL-2 family protein, MCL-1. Together, these results demonstrate that Legionella- infected macrophages are specifically and acutely sensitive to apoptotic cell death following the loss, or inhibition, of BCL-XL. Thus, the re-purposing of existing drugs, such as chemotherapeutic BH3-mimetics, to target host, rather than bacterial, pathways represents a novel and promising strategy for the treatment of intracellular pathogens that show increased, and often rapidly acquired, antibiotic resistance

Programmed cell death in Legionella infection

Legionella ssp. are the causative agents of severe inflammatory pneumonia, known as Legionnaires’ Disease, which is fatal in up to 30 % of cases. Legionella replicate within alveolar macrophages by hijacking host cell pathways to establish a unique vacuolar niche. This includes the regulation of programmed host cell death factors, as Legionella must first prevent, and then induce, host cell death to promote bacterial growth and egress, respectively. However, the molecular mechanisms involved in toggling “off” and “on” host cell death signalling pathways remain undetermined. The major focus of the work described in this thesis was the delineation of the role that programmed host cell death pathways play in Legionella infection. To do this, a novel live-cell imaging technique was employed to visualise the intracellular life-cycle of Legionella and to monitor macrophage health in real-time. Using this method, I was able to confirm that wild-type Legionella induce a rapid form of cell death, termed pyroptosis, which is dependent on bacterial flagellin and the host protease, caspase-1. While flagellin/caspase-1-mediated pyroptosis prevents bacterial replication, I have identified that aflagellated Legionella also induce caspase-11-dependent pyroptosis. In contrast to caspase-1, caspase-11-mediated pyroptosis is induced in the late stages of infection, concomitant with Legionella egress, and does not interfere with intracellular bacterial replication. Legionella are also thought to induce other forms of host cell death, however, genetic ablation of mitochondrial apoptosis (BAX and BAK deletion), caspase-independent necroptotic cell death (RIPK3 and MLKL deletion), or BNIP3 and BCL-RAMBO, the putative targets of the effector protein SidF, did not affect Legionella replication or the killing of host macrophages. Legionella must prevent the activation of host cell death signalling to allow for efficient replication. While down-regulation of flagellin enables intracellular growth in the presence of caspase-1, little is known about how Legionella might evade apoptotic cell death. Using live-cell imaging, I have now shown that Legionella-infected macrophages depend critically upon the anti-apoptotic activity of host cell BCL-XL, but not other BCL-2 family members, for viability. In the absence of BCL-XL, Legionella-infected cells underwent apoptosis, which abolished bacterial replication and dissemination. Legionella infection could be fully restored by inhibiting mitochondrial apoptosis, either via BAX/BAK deletion or caspase inhibition. A single dose of BCL-XL-targeted BH3-mimetic therapy significantly reduced Legionella burden in the lungs of mice and prevented lethal bacterial infection. Mechanistically, I identified that Legionella infection inhibits host protein synthesis, which sensitises macrophages to BCL-XL loss or inhibition, via depletion of another anti-apoptotic BCL-2 family protein, MCL-1. Together, these results demonstrate that Legionella- infected macrophages are specifically and acutely sensitive to apoptotic cell death following the loss, or inhibition, of BCL-XL. Thus, the re-purposing of existing drugs, such as chemotherapeutic BH3-mimetics, to target host, rather than bacterial, pathways represents a novel and promising strategy for the treatment of intracellular pathogens that show increased, and often rapidly acquired, antibiotic resistance

Targeting RIP Kinases in Chronic Inflammatory Disease

Chronic inflammatory disorders are characterised by aberrant and exaggerated inflammatory immune cell responses. Modes of extrinsic cell death, apoptosis and necroptosis, have now been shown to be potent drivers of deleterious inflammation, and mutations in core repressors of these pathways underlie many autoinflammatory disorders. The receptor-interacting protein (RIP) kinases, RIPK1 and RIPK3, are integral players in extrinsic cell death signalling by regulating the production of pro-inflammatory cytokines, such as tumour necrosis factor (TNF), and coordinating the activation of the NOD-like receptor protein 3 (NLRP3) inflammasome, which underpin pathological inflammation in numerous chronic inflammatory disorders. In this review, we firstly give an overview of the inflammatory cell death pathways regulated by RIPK1 and RIPK3. We then discuss how dysregulated signalling along these pathways can contribute to chronic inflammatory disorders of the joints, skin, and gastrointestinal tract, and discuss the emerging evidence for targeting these RIP kinases in the clinic

Effects of Valproic Acid and Dexamethasone Administration on Early Bio-Markers and Gene Expression Profile in Acute Kidney Ischemia-Reperfusion Injury in the Rat

<div><p>Renal ischemia-reperfusion (IR) causes acute kidney injury (AKI) with high mortality and morbidity. The objective of this investigation was to ameliorate kidney IR injury and identify novel biomarkers for kidney injury and repair. Under general anesthesia, left renal ischemia was induced in Wister rats by occluding renal artery for 45 minutes, followed by reperfusion and right nephrectomy. Thirty minutes prior to ischemia, rats (n = 8/group) received Valproic Acid (150 mg/kg; VPA), Dexamethasone (3 mg/kg; Dex) or Vehicle (saline) intraperitoneally. Animals were sacrificed at 3, 24 or 120 h post-IR. Plasma creatinine (mg/dL) at 24 h was reduced (P<0.05) in VPA (2.7±1.8) and Dex (2.3±1.2) compared to Vehicle (3.8±0.5) group. At 3 h, urine albumin (mg/mL) was higher in Vehicle (1.47±0.10), VPA (0.84±0.62) and Dex (1.04±0.73) compared to naïve (uninjured/untreated control) (0.14±0.26) group. At 24 h post-IR urine lipocalin-2 (μg/mL) was higher (P<0.05) in VPA, Dex and Vehicle groups (9.61–11.36) compared to naïve group (0.67±0.29); also, kidney injury molecule-1 (KIM-1; ng/mL) was higher (P<0.05) in VPA, Dex and Vehicle groups (13.7–18.7) compared to naïve group (1.7±1.9). Histopathology demonstrated reduced (P<0.05) ischemic injury in the renal cortex in VPA (Grade 1.6±1.5) compared to Vehicle (Grade 2.9±1.1). Inflammatory cytokines IL1β and IL6 were downregulated and anti-apoptotic molecule BCL2 was upregulated in VPA group. Furthermore, kidney DNA microarray demonstrated reduced injury, stress, and apoptosis related gene expression in the VPA administered rats. VPA appears to ameliorate kidney IR injury via reduced inflammatory cytokine, apoptosis/stress related gene expression, and improved regeneration. KIM-1, lipocalin-2 and albumin appear to be promising early urine biomarkers for the diagnosis of AKI.</p></div

Histopathology of hematoxylin and eosin stained kidney sections.

<p>A, B, C = Renal cortex at 3 hours (h) post ischemia-reperfusion (IR); D, E, F = Renal outer medulla at 24 h post-IR; A, D = Vehicle (saline control); B, E = Valproic acid (VPA); C, F = Dexamethasone (Dex) treated animals. Three high power fields (400x) representing approximately 50 tubules from cortex and outer medulla of each kidney were evaluated for ischemic changes (injury), tubular necrosis and regenerative changes. Collectively kidney injury and regeneration were graded (0–4) based on the mean percentage of tubules affected: 0, None; 1, <25%; 2, ≥25 but <50%; 3, ≥50 but <75%; 4, >75–100%. Ischemic changes included nuclear condensation <b>(nc)</b>, cytoplasmic eosinophilia, individual cell necrosis and tubular dilation <b>(td)</b>; tubular necrosis <b>(tn)</b> included confluent cell necrosis or sloughing of the tubular epithelium; and regenerative changes included tubular dilation, cytoplasmic basophilia and contraction of the cytoplasm, as well as vesicular chromatin with nucleoli. Hemorrhage <b>(hg)</b> was predominant in the vehicle control group. G, H, I = represent Histopathology quantification: renal cortex (black bars ■) and renal outer medulla (white bars □). The histologic injury score was significantly (P<0.05) lower in the VPA treated group compared to the Vehicle control at 3 h post-IR (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0126622#pone.0126622.t003" target="_blank">Table 3</a>).</p