Viral hepatitis amidst COVID-19 in Africa: Implications and recommendations

Hepatitis, a significant cause of mortality worldwide, results in around 1.34 million deaths each year globally. Africa is not exempt from the plague of Hepatitis. Around 100 million estimated individuals are infected with Hepatitis B or C. Egypt has the highest prevalence of cases of Hepatitis followed by Cameroon and Burundi. The continent is severely affected by the onset of the COVID-19 pandemic, as the virus has added an additional burden on the already fragile continent. With the pandemic, it is presumable that Hepatitis like other viral diseases will pose a threat to collapsing healthcare system. Therefore, for Africa to become more resilient in the face of such menaces, including Hepatitis, further prevention policies are required to be implemented     

BLT1-mediated T cell trafficking is critical for rejection and obliterative bronchiolitis after lung transplantation

Leukotriene B4 is a lipid mediator that recently has been shown to have potent chemotactic activity for effector T lymphocytes mediated through its receptor, BLT1. Here, we developed a novel murine model of acute lung rejection to demonstrate that BLT1 controls effector CD8+ T cell trafficking into the lung and that disruption of BLT1 signaling in CD8+ T cells reduces lung inflammation and mortality in the model. In addition, we used BLT1-deficient mice and a BLT1 antagonist in two tracheal transplant models of lung transplantation to demonstrate the importance of BLT1 for the recruitment of T cells into tracheal allografts. We also show that BLT1-mediated CD8+ T cell recruitment plays an important role in the development of airway fibroproliferation and obliteration. Finally, in human studies of lung transplant recipients, we found that BLT1 is up-regulated on T lymphocytes isolated from the airways of patients with obliterative bronchiolitis. These data demonstrate that BLT1 contributes to the development of lung rejection and obliterative bronchiolitis by mediating effector T lymphocyte trafficking into the lung. This is the first report that describes a pathologic role for BLT1-mediated T lymphocyte recruitment in disease and identifies BLT1 as a potential therapeutic target after lung transplantation.     

Surgical treatment of intrahepatic cholangiocarcinoma in the USA

Cholangiocarcinoma (CC) is a malignancy that arises from the epithelial cells of the biliary system (ductules as well as large ducts, and likely from progenitor cells, as well). Intrahepatic CC (ICC) is the second most common primary hepatic malignancy after hepatocellular carcinoma (HCC), and accounts for 10–15% of primary liver cancers. ICC differs from both extrahepatic and CC and HCC and has unique risk factors, histological features, genetic alterations and clinical outcomes. The natural history and results of surgical intervention are not well described as ICC is a relatively uncommon tumor, especially in the USA. This article reviews the literature relevant to the surgical management and outcome of patients with ICC in the USA.     

NhaA antiporter functions using 10 helices,and an additional 2 contribute to assembly/stability

The Escherichia coli Na⁺/H⁺ antiporter (Ec-NhaA) is the best-characterized of all pH-regulated Na⁺/H⁺ exchangers that control cellular Na⁺ and H⁺ homeostasis. Ec-NhaA has 12 helices, 2 of which (VI and VII) are absent from other antiporters that share the Ec-NhaA structural fold. This α-hairpin is located in the dimer interface of the Ec-NhaA homodimer together with a β-sheet. Here we examine computationally and experimentally the role of the α-hairpin in the stability, dimerization, transport, and pH regulation of Ec-NhaA. Evolutionary analysis (ConSurf) indicates that the VI–VII helical hairpin is much less conserved than the remaining transmembrane region. Moreover, normal mode analysis also shows that intact NhaA and a variant, deleted of the α-hairpin, share similar dynamics, suggesting that the structure may be dispensable. Thus, two truncated Ec-NhaA mutants were constructed, one deleted of the α-hairpin and another also lacking the β-sheet. The mutants were studied at physiological pH in the membrane and in detergent micelles. The findings demonstrate that the truncated mutants retain significant activity and regulatory properties but are defective in the assembly/stability of the Ec-NhaA dimer.Living cells are critically dependent on processes that regulate intracellular pH, Na⁺, and volume (1), and Na⁺/H⁺ antiporters play a primary role in these homeostatic mechanisms (reviewed in ref. 2). These antiporters are found in the cytoplasmic and intracellular membranes of most organisms (reviewed in refs. 3–6), and they have long been human drug targets (7).The principal Na⁺/H⁺ antiporter in Escherichia coli, Ec-NhaA, is responsible for intracellular Na⁺ and H⁺ homeostasis (8), and homologs have recently been implicated in the virulence of pathogenic bacteria (9). In humans, orthologs have been suggested to be involved in essential hypertension (10), as well as diabetes (11).Ec-NhaA is characterized by exceptionally high transport activity (12), a stoichiometry of 2H⁺/Na⁺ (13), and strong pH dependence (12), a property shared with other prokaryotic (8) and eukaryotic Na⁺/H⁺ antiporters (reviewed in refs. 3–6). Crystal structures of down-regulated Ec-NhaA at acidic pH (14) (Fig. 1) reveal a unique structural fold shared by a growing number of secondary transporters (15, 16, 17).Open in a separate windowFig. 1.(A) Evolutionary conservation analysis of Ec-NhaA. The crystal structure of Ec-NhaA, in ribbon representation, as seen in the plane of the membrane, represented with gray outlines, with the intracellular side facing up. ConSurf analysis (consurf.tau.ac.il) was carried out using PDB ID code 1ZCD (14). The amino acids are colored by their conservation grades using the color-coding bar, with cyan through maroon indicating variable through conserved. Overall, helices VI and VII, denoted with roman numerals, are of the least conserved TM helices with average conservation scores of 1 and 5, respectively, according to the ConSurf scoring method. The sites of the three single amino acid mutations Q47C, S246C, and V254C and the two sites in which Ec-NhaA was truncated (A182 on and A218 on) are shown as spheres (B) Ec-NhaA dimer. The crystal structure of the Ec-NhaA dimer (27), PDB ID code 4AU5, in ribbon representation as seen from the cytoplasm, with TM helices numbered as in A. The first monomer is colored light blue and the second colored wheat. The α-hairpin (composed of helices VI and VII) and β-sheet of one monomer are highlighted in marine and in the other monomer in orange. The red dashed line marks the boundary between the two functional domains of the transporter, the core domain to the left and the panel/dimer interface to the right. As can be seen the α- and β-hairpins constitute the dimer interface. (C) Close-up view on the interaction between the monomers. The Ec-NhaA dimer interface is shown as ribbon representation, with monomers colored as in B. Although the β-hairpin contributes the majority of interactions between subunits from the extracellular side, there is also a small interface between the cytoplasmic ends of helix VII of one monomer and helix IX of the other. This interaction probably involves hydrogen bond and hydrophobic contacts and forms a zipper-like structure consisting of R204 and L210 of one monomer and V254 and W258 of the other (27). The figures were generated using PyMol (PyMOL Molecular Graphics System, version 1.7.4; Schrödinger, LLC) (47, 48).Omitting transmembrane segments (TMs) VI and VII, the remaining 10 TMs of monomeric Ec-NhaA are organized into a highly conserved, densely packed core domain composed of two structurally related helix bundles (TMs III, IV, and V and TMs X, XI, and XII) that are topologically inverted with respect to each other (Fig. 1B) (14). TMs IV and XI are each interrupted by an unwound chain that crosses the other chain in the middle of the membrane, leaving two short helices oriented toward the cytoplasm (c) or the periplasm (p) (IVc, IVp and XIc, XIp, respectively; Fig. 1) (14). This noncanonical TM assembly—the NhaA fold—creates a delicately balanced electrostatic environment in the middle of the membrane at the ion binding site(s), which likely plays a critical role in cation exchange activity. The other TMs—the dimer interface domain—comprise a bundle along the dimer interface and also contain inverted-topology repeats (TMs I, II and VIII, IX; Fig. 1B) (18).Interestingly, the Na⁺/H⁺ antiporter structures that share the NhaA fold are characterized by different numbers of TMs from 12 to 13 (16, 17, 19) and are dimeric like Ec-NhaA. However, two prokaryotic ASBT (apical sodium-dependent bile acid transporter, also known as SLC10A2) symporters share the NhaA fold but have only 10 TMs; they lack the Ec-NhaA equivalents of helices VI and VII (20, 21). The ASBTs also differ from Ec-NhaA in that they are Na⁺/bile acid symporters. In addition, the ASBTs are monomeric. Taken together, the data raise questions regarding the role of TMs VI and VII in Ec-NhaA.In Ec-NhaA, helices VI and VII, which form an α-hairpin, are located in the dimer interface (Fig. 1 B and C). Therefore, these substructures may contribute to NhaA dimerization and/or stability; however, data in this regard are not available. In the current study, we constructed an NhaA mutant deleted of TMs VI and VII and studied its properties at physiological pH. The mutant devoid of TMs VI and VII is defective with respect to dimerization and/or stability but exhibits decreased but significant transport activity, as well as pH regulation.     

Granulocyte-macrophage colonies in cultures of human fetal liver cells: morphologic and ultrastructural analysis of proliferation and differentiation

Fetal liver cells from 6-12-week-old human fetuses were cultured in soft agar to study growth patterns of the granulocyte-macrophage colony forming cells (CFU(c)) and to characterize the cellular components of these colonies by morphologic, cytochemical and ultrastructural methods. Liver cell suspensions prepared from 31 fetuses obtained by vaginal interruptions of pregnancies, were seeded in soft agar over feeder layers of normal human leukocytes. At all gestational ages examined, agar colony numbers ranged from 44 +/- 15 to 89 +/- 44/2 x 10(5) cells seeded. Colony frequencies, size and gross morphology closely resembled those derived from adult human marrow. Morphologic, cytochemical and ultrastructural examinations showed that 92% of the colonies were granulocytic with incomplete maturation, as found in adult human marrow colonies. Density fractionation of the cells produced a low density cellular fraction which gave a 3- to 5-fold improved cloning efficiency. This study shows that human fetal livers of 6-12 weeks gestational age contain CFU(c) comparable to that found in adult marrow in their frequency, size, density and dependence on colony stimulating factor, and which differentiate mainly into mature or immature granulocytes. It is suggested that the lack of granulopoiesis in vivo in the early human fetal liver is probably not related to CFU(c) deficiency or defective differentiation. An alternative explanation involving impaired regulatory mechanism(s) should be sought.     

Glucoregulatory hormone influence on hepatic glucose production in the elderly

Hepatic glucose production was measured by tracer method in 9 elderly and 9 young subjects after an overnight fast. Blood samples were analyzed for glucoregulatory hormone levels. Hepatic glucose production was similar in elderly and young subjects. Significant hormone changes in the elderly included higher glucose and insulin levels and decreased glucagon. Nonsignificant decreases were seen in cortisol and urinary catecholamines, as well as a nonsignificant increase in growth hormone values. However, growth hormone was significantly correlated with hepatic glucose production in elderly (r = 0.79; p < 0.005), but not in young subjects. We conclude that elderly subjects are able to maintain normal hepatic glucose production despite changes in glucoregulatory hormones. The rate of hepatic glucose production may be related to growth hormone level in elderly, but not in young subjects.