R. L. Jansing

Influence of Δ9-tetrahydrocannabinol on cell proliferation and macromolecular biosynthesis in human cells

Abstract To elucidate the influence of Δ 9 -tetrahydrocannabinol ( Δ 9 -THC) on proliferation of human cells and macromolecular biosynthetic events associated with the proliferative process, we have examined the following parameters of Δ 9 -THC-treated HeLa S 3 cells grown in suspension culture: (1) exponential population growth, (2) subcellular localization of the drug, (3) protein, DNA and RNA synthesis, (4) composition and metabolism of chromosomal proteins, and (5) chromatin transcription in vitro . Exponentially growing HeLa S 3 cells exhibit a dose-dependent depression in proliferative activity when exposed to concentrations of Δ 9 -THC ranging from 5 to 40 μM. Approximately 9 per cent of the compound added to suspension cultures went into the cells, and of this, approximately 99 per cent was recovered from the cytoplasmic fraction and approximately 1 per cent from the nuclear fraction. The total cellular amount of Δ 9 -THC was calculated to be 1.44 ng/10 3 cells. Treatment of cells with 10–40 μM Δ 9 -THC resulted in a dose-dependent decrease in the apparent synthesis of DNA and RNA as well as in the sizes of the radiolabeled intracellular acid-soluble nucleotide precursor pool. Similar results were observed in the protein-synthesizing ability of cells treated with 30–40 μM concentrations of Δ 9 -THC. Template activity in vitro of chromatin was not affected by treatment of the cells with 10–30 μM concentrations of the drug. Polyaclylamide gel electrophoretic analysis of chromosomal proteins pulse labeled with [ 3 H] l -leucine suggests that Δ 9 -THC does not affect the composition, the rates of synthesis, or the turnover of histones and nonhistone chromosomal proteins.

Nonhistone Chromosomal Proteins and Histone Gene Transcription

Publisher Summary This chapter discusses that throughout the cell cycle of continuously dividing cells, as well as after the stimulation of nondividing cells to proliferate, a complex and interdependent series of biochemical events occur requiring modifications in the expression of information encoded in the genome. Hence, the cell cycle provides an effective model system for studying the regulation of gene readout. For the past several years, the laboratory has been focusing on the cell-cycle, stage-specific regulation of a defined set of genetic sequences—that coding for the histones. The chapter reviews that in continuously dividing cells as well as after stimulation of nondividing cells to proliferate, (1) regulation of histone gene expression resides, at least in part, at the transcriptional level, and (2) a subset of the nonhistone chromosomal proteins associated with the genome during the S-phase of the cell cycle is responsible for activation of histone gene transcription when DNA replication occurs.

CANNABINOIDS: THE INFLUENCE ON CELL PROLIFERATION AND MACROMOLECULAR BIOSYNTHESIS

Summary We have examined the influence of psychoactive (Δ9-THC, Δ8-THC, 11-OH-Δ9-THC) and nonpsychoactive (cannabinol) cannabinoids on proliferation of human cells (HeLa S3 cells grown in suspension culture) and on biochemical events associated with the proliferative process. The four cannabinoids studied brought about a dose-dependent inhibition in the rate of cell growth. Pulse-labeling studies indicated a cannabinoid-induced decrease in incorporation of 3H-thymidine, 3H-uridine and 3H-leucine into DNA, RNA and protein, respectively, in intact cells and a comparable decrease in the acid-soluble intracellular precursor pools was observed. Results from in vitro nuclear and chromatin transcription experiments did not suggest a drug-induced change in RNA synthesis. It therefore appears that quantitative alterations in the synthesis and/or turnover of nucleic acids and proteins do not result from cannabinoid treatment of HeLa cells. However, other data suggest that cannabinoids affect the synthesis of specific macromolecules. Since modifications in gene expression during the cell cycle are prerequisite for DNA replication and mitosis, the influence of cannabinoids on the structural and functional properties of the genome were examined. The four cannabinoids studied did not alter the staining pattern as observed on polyacrylamide gels of chromosomal proteins—histones and nonhistone chromosomal proteins—in HeLa cell chromatin. However, treatment of HeLa cells with psychoactive and nonpsychoactive cannabinoids resulted in changes in the incorporation of 3H-leucine into histone fractions and into specific molecular weight classes of nonhistone chromosomal proteins; acetylation and phosphorylation of chromosomal proteins were also altered.