Chromatin phospholipid changes during rat liver development

Albi, Elisabetta; Magni, Mariapia Viola; Lazzarini, Remo; Gahan, P. B.

doi:10.1002/cbf.290090209

Cited by 23 publications

(16 citation statements)

References 14 publications

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“…This conclusion is in agreement with the observation that in newborn rats, during hepatocyte biochemical maturation, the chromatin PLs were at a higher percentage with respect to the adult rats ( Fig. 3) with especially two PLs being higher: PS and SM (Albi et al, 1991). No similar results were observed in the microsomal and in the nuclear fractions.…”

Section: Intranuclear Lipid Fraction Characteristicssupporting

confidence: 92%

“…In regenerating liver, PS synthesis increased strongly when the DNA synthesis started (unpublished data). PS increased during hepatocyte maturation (Albi et al, 1991) and was lost from the nuclei digested with RNase and DNase (Albi et al, 1996). In fact, after this treatment, the RNA decreased by 74% and the PLs content decreased by 48%; in particular, PS showed a decrease of 45%.…”

Section: Phosphatidylserine Rolementioning

confidence: 95%

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The role of intranuclear lipids

Albi¹,

Magni²

2004

Biology of the Cell

137

124

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The presence of phospholipids as a component of chromatin is now well documented and many enzymes such as sphingomyelinase, sphingomyelin-synthase, reverse sphingomyelin-synthase and phosphatidylcholine-dependent phospholipase C have been described and characterised. Other lipids were demonstrated inside the nucleus especially plasmalogens and cholesterol. The chromatin phospholipids, comprising 10% of that present in the nucleus, show a different metabolism with respect to those present in either microsomes or in nuclear membranes; they increase also during the DNA duplication as shown during both liver regeneration and cell maturation. They appear localised near newly synthesized RNA in decondensed chromatin. Digestion of chromatin with RNase, but not with DNase, causes a loss of phospholipids. The composition of the chromatin phospholipid fraction shows an enrichment in sphingomyelin and phosphatidylserine. In this review the behaviour of single lipids in relation to cell proliferation, cell differentiation and apoptosis is described. Sphingomyelin, the lipid most represented in chromatin with respect to microsomes and nuclear membranes, is localised near to newly synthesized RNA, its presence appearing to protect RNA from RNase digestion. This effect is reversed by sphingomyelinase which digests sphingomyelin and, as a consequence, RNA may be hydrolysed. The amount of sphingomyelin is restored by sphingomyelin-synthase. Sphingomyelin increases during the differentiation process and apoptosis. An increase of sphingomyelinase with consequent decrease in sphingomyelin is observed at the beginning of S-phase of the cell cycle. A possible role in stabilising the DNA double helix is indicated. Phosphatidylserine behaves similarly during differentiation and appears to stimulate both RNA and DNA polymerases. Phosphatidylcholine is implicated in cell proliferation through the activation of intranuclear phosphatidylcholine-dependent phospholipase C and diacylglycerol production. The increase in diacylglycerol stimulates phosphatidylcholine synthesis through the major pathway from cytidyltriphosphate. An inhibition of phosphatidylcholine synthesis is responsible for the initiation of apoptosis. The presence of reverse sphingomyelin-synthase favours the formation of phosphatidylcholine, the donor of phosphorylcholine, from sphingomyelin. Little information has been reported for phospatidylethanolamine, but phosphtidylinositol appears to influence cell differentiation and proliferation. This last effect is due to the action of two enzymes: PI-PLCß1 having a role in the onset of DNA synthesis and PC-PLCc1 acting in G2 transit. Phosphoinositides also may have an important role: in membrane-stripped nuclei isolated from mitogen stimulated cells a decrease in PIP and PIP2 followed by an increase in diacylglycerol and a translocation of protein kinase C inside the nucleus is observed. On the other hand, overexpression of the enzyme inositol polysphosphate-1-phosphatase reduced DNA synthesis by 50%. Nevertheless, an en...

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Section: Intranuclear Lipid Fraction Characteristicssupporting

confidence: 92%

Section: Phosphatidylserine Rolementioning

confidence: 95%

The role of intranuclear lipids

Albi¹,

Magni²

2004

Biology of the Cell

137

124

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“…The products of PL metabolism may act also as internal signals by activating other nuclear proteins such as PKC or favouring the synthesis of polymerases through the presence of PS (Albi et al 1991). Albi and Viola-Magni (2002) have demonstrated the presence of CHO in hepatocyte chromatin.…”

Section: The Roles Of Phospholipid-associated Enzymes In Normal Hepatmentioning

confidence: 99%

Possible Roles of Nuclear Lipids in Liver Regeneration

Viola-Magni¹,

Gahan²

2012

Liver Regeneration

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“…In both newborn and 6-day-old rats, the SM is 9.5-9.9% of the PLs present in the chromatin decreasing to 3.9% in 45-dayold animals. 21 This period of life corresponds to the biochemical maturation of hepatocytes. 22 Using the acid hematein test, modified for electron microscopy, and phospholipase A2-colloidal gold method, electron microscopy showed that PLs were located mainly at the border between condensed and dispersed chromatin.…”

Section: Sphingomyelin Presence and Localizationmentioning

confidence: 99%

Chromatin‐associated sphingomyelin: metabolism in relation to cell function

Albi¹,

Magni²

2003

Cell Biochemistry & Function

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After the first histochemical demonstration by Chayen and Gahan of the presence of phospholipids and especially of sphingomyelin in chromatin, this became the object of long debate and of contradictory results. The general conclusion was that the presence of phospholipids may due to contamination during the isolation of chromatin. More recently the existence of a phospholipid chromatin fraction was confirmed by demonstrating that isolated hepatocyte nuclei, labelled by saturated and unsaturated radioiodination method, showed the presence of radioactivity only in the membrane and not in the isolated chromatin. The phospholipid composition showed an enrichment in sphingomyelin which increased during hepatocyte maturation or erythroleukemic cell differentiation induced by DMSO. A decrease in sphingomyelin was observed at the beginning of the Sphase in regenerating liver or in cultured proliferating cells. These changes were due to the presence of sphingomyelinase and sphingomyelin synthase in the chromatin, the activity of which paralleled the variation in sphingomyelin content. The sphingomyelin was co-localized with RNA as shown by biochemical and electron microscopy methods. Using bromo-uridine it was demonstrated that labelled RNA and sphingomyelin were present in actively transcribing nuclear regions. Isolated nuclear complexes after DNase and RNase digestion contained not only protein, but also RNA and sphingomyelin. After hydrolysis of sphingomyelin the RNAse-resistant RNA becomes RNAse sensitive. It can therefore be concluded that sphingomyelin and the related enzymes are present in the chromatin; sphingomyelin may have a role in RNA transcription protecting RNA by RNAse digestion before its transfer to the cytoplasm.

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Chromatin phospholipid changes during rat liver development

Cited by 23 publications

References 14 publications

The role of intranuclear lipids

The role of intranuclear lipids

Possible Roles of Nuclear Lipids in Liver Regeneration

Chromatin‐associated sphingomyelin: metabolism in relation to cell function

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