The forgotten oral microbial transplantation for improving the outcomes of COVID-19

Ever since the uncovering of the severe discrepancy of COVID-19 manifestations, irrespective of viral load, scientists have raced to locate and manage factors contributing to the genesis of a critical state. Recent evidence delineates the role of oral dysbiosis in the development of low-grade inflammation, characterized by the increase of inflammatory cytokines common to those fundamental to the development of severe COVID. Furthermore, high periodontopathic bacteria were recorded in severe acute respiratory syndrome in COVID patients, as well as its common provoking comorbidities such as diabetes and hypertension. This can be explained by the immigration and elimination of oral bacteria into the airways, which, in the context of an injured lung, allows for their preferential overgrowth familiar to that, causing the progression to advanced lung diseases. This is why we indicate the promising usage of oral microbiome transplantation as a treatment of oral microbial dysbiosis, not only associated with the worst outcomes of COVID-19 but also in other disorders of low-grade inflammation.

Characterization of peroxisomal 3-hydroxy-3-methylglutaryl coenzyme A reductase in UT2 cells: sterol biosynthesis, phosphorylation, degradation, and statin inhibition

We have previously identified a CHO cell line (UT2 cells) that expresses only one 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase protein which is localized exclusively in peroxisomes [Engfelt, H.W., Shackelford, J.E., Aboushadi, N., Jessani, N., Masuda, K., Paton, V.G., Keller, G.A., and Krisans, S.K. (1997) J. Biol. Chem. 272, 24579-24587]. In this study, we utilized the UT2 cells to determine the properties of the peroxisomal reductase independent of the endoplasmic reticulum (ER) HMG-CoA reductase. We demonstrated major differences between the two proteins. The peroxisomal reductase is not the rate-limiting enzyme for cholesterol biosynthesis in UT2 cells. The peroxisomal reductase protein is not phosphorylated, and its activity is not altered in the presence of inhibitors of cellular phosphatases. Its rate of degradation is not accelerated in response to mevalonate. Finally, the degradation process is not blocked by N-acetyl-Leu-Leu-norleucinal (ALLN). Furthermore, the peroxisomal HMG-CoA reductase is significantly more resistant to inhibition by statins. Taken together, the data support the conclusion that the peroxisomal reductase is functionally and structurally different from the ER HMG-CoA reductase.

Role of peroxisomes in isoprenoid biosynthesis

Our group and others have recently demonstrated that peroxisomes contain a number of enzymes involved in cholesterol biosynthesis that previously were considered to be cytosolic or located in the endoplasmic reticulum (ER). Peroxisomes have been shown to contain HMG-CoA reductase, mevalonate kinase, phosphomevalonate kinase, phosphomevalonate decarboxylase, isopentenyl diphosphate isomerase, and FPP synthase. Four of the five enzymes required for the conversion of mevalonate to FPP contain a conserved putative PTS1 or PTS2, supporting the concept of targeted transport into peroxisomes. To date, no information is available regarding the function of the peroxisomal HMG-CoA reductase in cholesterol/isoprenoid metabolism, and the structure of the peroxisomal HMG-CoA reductase has yet to be determined. We have identified a mammalian cell line that expresses only one HMG-CoA reductase protein, and which is localized exclusively to peroxisomes, to facilitate our studies on the function, regulation, and structure of the peroxisomal HMG-CoA reductase. This cell line was obtained by growing UT2 cells (which lack the ER HMG-CoA reductase) in the absence of mevalonate. The surviving cells exhibited a marked increase in a 90-kD HMG-CoA reductase that was localized exclusively to peroxisomes. The wild-type CHO cells contain two HMG-CoA reductase proteins, the well-characterized 97-kD protein localized in the ER, and a 90-kD protein localized in peroxisomes. We have also identified the mutations in the UT2 cells responsible for the lack of the 97-kD protein. In addition, peroxisomal-deficient Pex2 CHO cell mutants display reduced HMG-CoA reductase levels and have reduced rates of sterol and nonsterol biosynthesis. These data further support the proposal that peroxisomes play an essential role in isoprenoid biosynthesis.

Analysis of isoprenoid biosynthesis in peroxisomal-deficient Pex2 CHO cell lines

ZR-78 and ZR-82 cells are two peroxisomal-deficient Chinese hamster ovary (CHO) cell mutants. These cells lack normal peroxisomes and show reduced levels of plasmalogen synthesis and other peroxisomal functions attributed to the deficiency of peroxisomal matrix enzymes. As we have recently identified two HMG-CoA reductase proteins in CHO cells, a 97 kDa reductase localized in the ER and a 90 kDa reductase protein localized in peroxisomes, this enabled us to study the two reductase proteins for the first time in peroxisomal-deficient CHO cells. In this study we report the results of a detailed analysis of the isoprenoid biosynthetic pathway in the peroxisomal-deficient CHO cell lines ZR-78 and ZR-82. We demonstrate that total HMG-CoA reductase activity is significantly reduced in the peroxisomal-deficient cells as compared to the wild type cells. Analysis of the two reductase proteins in permeabilized cells indicated that in the ZR-78 and ZR-82 cells the 90 kDa peroxisomal reductase protein was mainly localized to the cytosol. We further show that the rates of both sterol (cholesterol) and non-sterol (dolichols) biosynthesis were significantly lower in the peroxisomal-deficient cells, when either [3H] acetate or [3H] mevalonate was used as substrate. In contrast, the rate of dolichol biosynthesis in the peroxisomal-deficient cells was similar to that of the wild type cells when incubated with [3H] farnesol. In addition, we demonstrate that the peroxisomal-deficient cells exhibited increased rates of lanosterol biosynthesis as compared to wild type cells. The results of this study provide further evidence for the essential requirement of peroxisomes for cholesterol biosynthesis as well as for dolichol production.

Characterization of UT2 cells. The induction of peroxisomal 3-hydroxy-3-methylglutaryl-coenzyme a reductase

In the liver 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase is present not only in the endoplasmic reticulum but also in the peroxisomes. However, to date no information is available regarding the function of the peroxisomal HMG-CoA reductase in cholesterol/isoprenoid metabolism, and the structure of the peroxisomal HMG-CoA reductase has yet to be determined. We have identified a mammalian cell line that expresses only one HMG-CoA reductase protein and that is localized exclusively to peroxisomes. This cell line was obtained by growing UT2 cells (which lack the endoplasmic reticulum HMG-CoA reductase) in the absence of mevalonate. The cells exhibited a marked increase in a 90-kDa HMG-CoA reductase that was localized exclusively to peroxisomes. The wild type Chinese hamster ovary cells contain two HMG-CoA reductase proteins, the well characterized 97-kDa protein, localized in the endoplasmic reticulum, and a 90-kDa protein localized in peroxisomes. The UT2 cells grown in the absence of mevalonate containing the up-regulated peroxisomal HMG-CoA reductase are designated UT2*. A detailed characterization and analysis of this cell line is presented in this study.

Metabolism of farnesol: phosphorylation of farnesol by rat liver microsomal and peroxisomal fractions

In this study we provide evidence for the first time that rat liver microsomal and peroxisomal fractions are able to phosphorylate free farnesol to its diphosphate ester in a CTP dependent manner. The farnesyl diphosphate (FPP) kinase activity is decreased in whole liver homogenates obtained from rats treated with cholesterol and unchanged in homogenates obtained from rats treated with cholestyramine. In contrast, farnesyl pyrophosphatase (FPPase) activity, an enzyme which specifically hydrolyzes FPP to farnesol is only found in the microsomal fraction and is unaffected by treatment of rats with cholesterol or cholestyramine. In addition, we also demonstrate that farnesol can be oxidized to a prenyl aldehyde, presumably by an alcohol dehydrogenase (ADH), and that this activity resides in the mitochondrial and peroxisomal fractions.