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The effect of prostaglandin E2 and I2-analogues on mitogen induced lymphocyte stimulation
243
SELECTIVE REGULATION OF THE SYNTHESIS OF 1 AND 2 SERIES PROSTAGLANDINS: NUTRITIONAL AND PHARMACOLOGICAL REGULATION OF IMMUNITY. D.F. Horrobin, M. Oka and M.S. Manku PO Box lO, Nuns'
A NEW CONCEPT IN THE
5
Island, Montreal H3E IJ8, Canada.
Prostaglandins (PGs) may have both pro- and anti-inflammatory effects and may both enhance and inhibit immune responses. PGEI is found in large amounts in the thymus and may regulate T lymphocyte function. Drugs which inhibit synthesis of all PGs by blocking precursor mobilisation (like glucocorticoids) or by blocking the cyclo-oxygenase (like indomethacin) may provide symptomatic relief but do not usually favourably influence the long term course of human disorders of inflammation and immunity. We propose that many disorders of inflammation and immunity are not caused by over-production of all PGs but are associated with reduced synthesis of l series PGs (notably PGEI) and by increased formation of 2 series PGs. This idea is supported by the selective actions of certain agents known to influence the long term course of some human disorders of immunity. Levamisole, penicillamine and zinc selectively mobilise dihomogammalinolenic acid (DGLA) the precursor of PGEI but do not affect mobilisation of arachidonic acid. Colchicine at low, clinically relevant concentrations, and vitamin C both selectively enhance conversion of DGLA to PGEI in human platelets: Vitamin C has no effect on arachidonate conversion while colchicine actually inhibits thromboxane B2 formation. PGE2 is also able to enhance conversion of DGLA to PGEI and since PGEI is known to inhibit arachidonate mobilisation and 2 series PG synthesis, these two effects form the basis of a negative feedback loop which under normal conditions is self-regulating and maintains a balance between the I and 2 series. If for any reason PGEI formation is inadequate, there will be T lymphocyte failure and sustained elevation of production of 2 series PGs. Nutritional factors, including essential fatty acids, pyridoxine, zince and vitamin C are all required for normal PGEI synthesis. Levamisole, zinc, penicillamine and colchicine may all enhance PGEI synthesis selectively and this will be of value when PGEI formation would otherwise be inadequate. This new concept of the selective action of drugs and nutrients on the formation of PGEI and hence on the functioning of T lymphocytes may allow more rational employment of therapeutic measures.
THE EFFECT OF PROSTAGLANDIN E2 and 12-ANALOGUES ON MITOGEN INDUCED LYMPHOCYTESTIMULATION Ann Kingston*, J.E. Kay* and J. I v a n y i t *School of Biological Science, University of Sussex, U.K. and tDepartment of Experimental Immunobiology, The Wellcome Research Laboratories, Beckenham, Kent,U.K. Lymphocyte suspensions from pig and human peripheral blood were stimulated in microcultures with PHA or Concanavalin A and DNA synthesis was measured a f t e r 2-3 days by 3H-thymidine incorporation. Drugs at a wide range of concentrations were added e i t h e r at the onset or l a t e r to c u l t u re media. Mononuclear c e l l s (PBMC) from heparinized blood were compared with adherent c e l l - d e p l e t e d lymphocytes (PBL) prepared from d e f i b r i n a t e d pig blood using cotton wool columns. The results showed a pronounced reduction in the IDs0 dose of PGE2 for PBL when compared with PBMC. Furthermore the degree of i n h i b i t i o n of PBMC responses was much reduced when adding PGE2 20 hr a f t e r the onset of culture w h i l s t the suppression of PBL responses was s t i l l maintained during the same period. Increase in cell density between I-8 x IO s c e l l s per c u l t u r e resulted in gradual decline of PGE2 mediated suppression of 3H-thymidine uptake. Thus, decreased drug s e n s i t i v i t y occurred e i t h e r in the presence of monocytes or in high c e l l density cultures. Results s i m i l a r to those with PGE2 were obtained also f o r stable PGI2 analogues 6-~-carbaprostacyclin (U-55185) and a hydantoin compound (245C). The e f f e c t i v e IDso concentration of a l l three tested drugs in pig lymphocyte cultures varied between lO-S-lO-7M. Comparable i n h i b i t i o n of human lymphocyte s t i m u l a t i o n was observed only with PGE2 and U55185 whereas the hydantoin analogue was e f f e c t i v e only at higher concentrations. These findings indicate that exogenous prostaglandins share a common mechanism of action which seems to be modulated by the density and composition of the responding lymphocyte c u l t u r e .
6
SELECTIVE REGULATION OF THE SYNTHESIS OF 1 AND 2 SERIES PROSTAGLANDINS: NUTRITIONAL AND PHARMACOLOGICAL REGULATION OF IMMUNITY. D.F. Horrobin, M. Oka and M.S. Manku PO Box lO, Nuns'
A NEW CONCEPT IN THE
5
Island, Montreal H3E IJ8, Canada.
Prostaglandins (PGs) may have both pro- and anti-inflammatory effects and may both enhance and inhibit immune responses. PGEI is found in large amounts in the thymus and may regulate T lymphocyte function. Drugs which inhibit synthesis of all PGs by blocking precursor mobilisation (like glucocorticoids) or by blocking the cyclo-oxygenase (like indomethacin) may provide symptomatic relief but do not usually favourably influence the long term course of human disorders of inflammation and immunity. We propose that many disorders of inflammation and immunity are not caused by over-production of all PGs but are associated with reduced synthesis of l series PGs (notably PGEI) and by increased formation of 2 series PGs. This idea is supported by the selective actions of certain agents known to influence the long term course of some human disorders of immunity. Levamisole, penicillamine and zinc selectively mobilise dihomogammalinolenic acid (DGLA) the precursor of PGEI but do not affect mobilisation of arachidonic acid. Colchicine at low, clinically relevant concentrations, and vitamin C both selectively enhance conversion of DGLA to PGEI in human platelets: Vitamin C has no effect on arachidonate conversion while colchicine actually inhibits thromboxane B2 formation. PGE2 is also able to enhance conversion of DGLA to PGEI and since PGEI is known to inhibit arachidonate mobilisation and 2 series PG synthesis, these two effects form the basis of a negative feedback loop which under normal conditions is self-regulating and maintains a balance between the I and 2 series. If for any reason PGEI formation is inadequate, there will be T lymphocyte failure and sustained elevation of production of 2 series PGs. Nutritional factors, including essential fatty acids, pyridoxine, zince and vitamin C are all required for normal PGEI synthesis. Levamisole, zinc, penicillamine and colchicine may all enhance PGEI synthesis selectively and this will be of value when PGEI formation would otherwise be inadequate. This new concept of the selective action of drugs and nutrients on the formation of PGEI and hence on the functioning of T lymphocytes may allow more rational employment of therapeutic measures.
THE EFFECT OF PROSTAGLANDIN E2 and 12-ANALOGUES ON MITOGEN INDUCED LYMPHOCYTESTIMULATION Ann Kingston*, J.E. Kay* and J. I v a n y i t *School of Biological Science, University of Sussex, U.K. and tDepartment of Experimental Immunobiology, The Wellcome Research Laboratories, Beckenham, Kent,U.K. Lymphocyte suspensions from pig and human peripheral blood were stimulated in microcultures with PHA or Concanavalin A and DNA synthesis was measured a f t e r 2-3 days by 3H-thymidine incorporation. Drugs at a wide range of concentrations were added e i t h e r at the onset or l a t e r to c u l t u re media. Mononuclear c e l l s (PBMC) from heparinized blood were compared with adherent c e l l - d e p l e t e d lymphocytes (PBL) prepared from d e f i b r i n a t e d pig blood using cotton wool columns. The results showed a pronounced reduction in the IDs0 dose of PGE2 for PBL when compared with PBMC. Furthermore the degree of i n h i b i t i o n of PBMC responses was much reduced when adding PGE2 20 hr a f t e r the onset of culture w h i l s t the suppression of PBL responses was s t i l l maintained during the same period. Increase in cell density between I-8 x IO s c e l l s per c u l t u r e resulted in gradual decline of PGE2 mediated suppression of 3H-thymidine uptake. Thus, decreased drug s e n s i t i v i t y occurred e i t h e r in the presence of monocytes or in high c e l l density cultures. Results s i m i l a r to those with PGE2 were obtained also f o r stable PGI2 analogues 6-~-carbaprostacyclin (U-55185) and a hydantoin compound (245C). The e f f e c t i v e IDso concentration of a l l three tested drugs in pig lymphocyte cultures varied between lO-S-lO-7M. Comparable i n h i b i t i o n of human lymphocyte s t i m u l a t i o n was observed only with PGE2 and U55185 whereas the hydantoin analogue was e f f e c t i v e only at higher concentrations. These findings indicate that exogenous prostaglandins share a common mechanism of action which seems to be modulated by the density and composition of the responding lymphocyte c u l t u r e .
6