Novel insights into photoreception, phototransduction and biological rhythms how might this impact on carcinogenesis?

Transcription

1 Children with Leukaemia Scientific Conference Wednesday 8 th September 2004 Novel insights into photoreception, phototransduction and biological rhythms how might this impact on carcinogenesis? Russell G. Foster r.foster@ic.ac.uk

2 Successfully fighting cancer is dependent upon integrating information across a range of disciplines.

3 Children with Leukaemia Scientific Conference Wednesday 8 th September 2004 Novel insights into photoreception, phototransduction and biological rhythms how might this impact on carcinogenesis? Russell G. Foster r.foster@ic.ac.uk

4 Known links with cancer and the circadian system - fall under three interlinked categories

5 Links with cancer and the circadian system fall under three interlinked categories: (i) Treatment - Chronotherapy or the timed application of anti-cancer drugs. G. E. Rivard, C. Infante-Rivard, M. F. Dresse, J. M. Leclerc and J. Champagne. Circadian time-dependent response of childhood lymphoblastic leukemia to chemotherapy: A longterm follow-up study of survival, Chronobiol Int, 1993, 10, The study found that the risk of relapse was 2.56 times higher in children who received chemotherapy in the morning than in those receiving the same treatment in the evening.

6 Links with cancer and the circadian system fall under three interlinked categories: (ii) Cause - Circadian regulation of the cell cycle. L. Fu and C. C. Lee, The circadian clock: Pacemaker and tumour suppressor, Nat Rev Cancer, 2003, 3, The links between the circadian system and cell proliferation e.g. Per2-mutant mice more susceptible to cancer Per2 normally inhibits c-myc signalling pathway.

7 Links with cancer and the circadian system fall under three interlinked categories: (iii) Cause - Circadian disruption of due to abnormal environmental conditions. J. C. Li and F. Xu, Influences of light-dark shifting on the immune system, tumor growth and life span of rats, mice and fruit flies as well as on the counteraction of melatonin, Biol Signals, 1997, 6, Carcinoma-bearing rats showed increased tumour growth and reduced survival when kept under alternating light/dark (LD) cycles of 14L:10D followed by 10L:14D every 3 days Continued:

8 Schernhammer ES, Laden F, Speizer FE, Willett WC, Hunter DJ, Kawachi I, Fuchs CS, Colditz GA. Night-shift work and risk of colorectal cancer in the nurses' health study. J Natl Cancer Inst Jun 4;95(11): Sephton S, Spiegel D Circadian disruption in cancer: a neuroendocrine-immune pathway from stress to disease? Brain Behav Immun Oct;17(5): Davis S, Mirick DK, Stevens RG Night shift work, light at night, and risk of breast cancer. J Natl Cancer Inst Oct 17;93(20):

9 One environmental factor that can be linked to all three of these categories of cancer and the circadian system is light

10 Light adjusts the clock to the appropriate phase of the circadian cycle for chronopharmacology

11 Light adjusts the clock to the appropriate phase of the circadian cycle for chronopharmacology Light alters the expression of certain clock genes which in-turn regulate the cell cycle

12 Light adjusts the clock to the appropriate phase of the circadian cycle for chronopharmacology Light alters the expression of certain clock genes which in-turn regulate the cell cycle Light exposure is primarily responsible for the synchronisation of the circadian system, and through abnormal exposure to light, circadian disruption

13 Is abnormal light exposure a risk factor for childhood leukaemia?

14 Is abnormal light exposure a risk factor for childhood leukaemia? Better understanding of the mechanisms whereby light regulates the circadian system

15 The Circadian System SCN (Suprachiasmatic nuclei) The time-signal that coordinates rhythmicity in physiology and behaviour

16 The Circadian System A clock is not a clock unless it is set to local time! Eye SCN (Suprachiasmatic nuclei) Light is the primary zeitgeber - changes in the quantity and quality of light at dawn and dusk.

17 Behaviour Activity Sleep/wake Endocrine Melatonin Cortisol Eye SCN Peripheral oscillators Heart Liver Lung

18 Behaviour Activity Sleep/wake Endocrine Melatonin Cortisol Eye SCN Peripheral oscillators Heart Liver Lung

19 The receptor mechanisms that adjust the clock to the light/dark cycle are complex and involve non rod, noncone photoreceptors.

20 Non-rod, non-cone photoreception in the vertebrate eye A novel ocular photoreceptor? What is the nature of the novel photopigment? Which retinal neurones are photosensitive? What about melanopsin? Is melanopsin the circadian photopigment?

21 The rodless + coneless mouse (rd/rd cl) X rd/rd cl/

22 Circadian Adjustment to the Light Cycle Responses to a single 15 min. light pulse are broadly similar between +/+ and rd/rd cl mice Freedman, M. S., Lucas, R. J., Soni, B., von Schantz, M., Munoz, M., David Gray, Z. K. and Foster, R. G. (1999). Regulation of mammalian circadian behavior by non rod, non cone, ocular photoreceptors. Science 284, Lucas, R. J., Freedman, M. S., Munoz, M., Garcia Fernandez, J. M. and Foster, R. G. (1999). Regulation of the mammalian pineal by non rod, non cone, ocular photoreceptors. Science 284,

23 The eye contains a non-rod, non-cone photoreceptor that regulates the circadian system and probably a range of other physiological responses to light.

24 Sleep - Photic modulation of VLPO activity in the rd/rd cl mouse min X4 fold induction of Fos by light in the VLPO Sham Light

25 Non-rod, non-cone photoreception in the vertebrate eye A novel ocular photoreceptor? What is the nature of the novel photopigment? Which retinal neurones are photosensitive? What about melanopsin? Is melanopsin the circadian photopigment?

26 Describing the spectral sensitivity or action spectrum of any light dependent response is a critical step in characterising the photopigments upon which the response is based you can deduce biochemistry.

27 Action Spectrum for Phase Shifting Circadian Locomotor Rhythms in rd/rd cl mice. Novel Opsin with a λmax ~ 480 nm Hattar, S., Lucas, R.J., Mrosovsky, N., Thompson, S., Douglas, R.H., Hankins, M.W., Lem, J., Biel, M., Hofmann, F., Foster, R.G. & Yau, K.W. Melanopsin and rod-cone photoreceptive systems account for all major accessory visual functions in mice. Nature, (2003)

28 Action Spectrum for Phase Shifting Circadian Locomotor Rhythms in rd/rd cl mice. Novel Opsin with a λmax ~ 480 nm Hattar, S., Lucas, R.J., Mrosovsky, N., Thompson, S., Douglas, R.H., Hankins, M.W., Lem, J., Biel, M., Hofmann, F., Foster, R.G. & Yau, K.W. Melanopsin and rod-cone photoreceptive systems account for all major accessory visual functions in mice. Nature, (2003)

29 ~ 480 nm = blue light photopigment

30 Flavoprotein Action Spectrum* log(% sensitivity) Opsin Template λmax 479nm Arabidopsis cry1** No direct evidence for a flavoprotein or cryptochrome based photopigment Wavelength (nm) * Phycomyces phototropism Smyth et al (1988) Progr Phycol Res 6: ** Action spectrum for hypocotyl elongation in cry1 overexpressing Arabidopsis Ahmad et al (2002) Plant Physiology 129:

31 Flavoprotein Action Spectrum* log(% sensitivity) Opsin Template λmax 479nm Arabidopsis cry1** No direct evidence for a flavoprotein or cryptochrome based photopigment Wavelength (nm) * Phycomyces phototropism Smyth et al (1988) Progr Phycol Res 6: ** Action spectrum for hypocotyl elongation in cry1 overexpressing Arabidopsis Ahmad et al (2002) Plant Physiology 129: Russell Van Gelder (Washington University School of Medicine) It would thus appear that the primary photopigment in nonvisual photoreception is opsindependent, but not cryptochrome-dependent (Panda et al., 2003).

32 Are we like mice?

33 rd/rd cl mouse pupil and circadian action spectra. Action spectra for melatonin suppression and cone ERG in humans. Data normalised and re plotted from: Brainard, G.C., Hanifin,, J.P., Greeson,, J.M., Byrne, B., Glickman, G., Gerner,, E., & Rollag,, M.D. (2001). Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor. J Neurosci,, 21,, Thapan,, K., Arendt, J., & Skene, D.J. (2001). An action spectrum for melatonin suppression: evidence for a novel non rod, non cone photoreceptor system in humans. J Physiol,, 535,, Hankins, M.W., & Lucas, R.J. (2002). The primary visual pathway in humans is regulated according to long term light exposure through the action of a non classical photopigment. Current Biology, 12,,

34 rd/rd cl mouse pupil and circadian action spectra. Action spectra for melatonin suppression and cone ERG in humans. Data normalised and re plotted from: Brainard, G.C., Hanifin,, J.P., Greeson,, J.M., Byrne, B., Glickman, G., Gerner,, E., & Rollag,, M.D. (2001). Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor. J Neurosci,, 21,, Thapan,, K., Arendt, J., & Skene, D.J. (2001). An action spectrum for melatonin suppression: evidence for a novel non rod, non cone photoreceptor system in humans. J Physiol,, 535,, Hankins, M.W., & Lucas, R.J. (2002). The primary visual pathway in humans is regulated according to long term light exposure through the action of a non classical photopigment. Current Biology, 12,,

35 Non-rod, non-cone photoreception in the vertebrate eye A novel ocular photoreceptor? What is the nature of the novel photopigment? Which retinal neurones are photosensitive? What about melanopsin? Is melanopsin the circadian photopigment?

36 Intrinsically Photosensitive Ganglion Cells Electrophysiology Calcium Imaging rd/rd cl retina DF/F 100 sec Sekaran et al. (2003) Berson et al. (2002)

37 Rods and cones ablated rd/rd cl

38 We observe different types of response Transient Sustained F/F 50 sec F/F 50 sec Repetitive F/F 50 sec

39 Pharmacological Studies % cells * Population is reduced by half when gap-junction coupling is blocked. Though the diversity of responses is unaffected. 0 control carbenoxalone Plexus or network of cells not all of which show direct photosensitivity

40 The Development of Inner Retinal Photoreceptors

41 Photosensitivity from birth before the rods and cones have developed! P0 time (sec) after lights on DF/F 50 sec 0 100% 4.7 x x x sec

42 Non-rod, non-cone photoreception in the vertebrate eye A novel ocular photoreceptor? What is the nature of the novel photopigment? Which retinal neurones are photosensitive? What about melanopsin? Is melanopsin the circadian photopigment?

43 The photosensitive retinal ganglion cells (RGCs)) that project to the SCN express melanopsin!

44 What happens to circadian responses to light if the rods, cones, and melanopsin are all ablated in the same animal? Lucas, R.J., Hattar, S., Takao, M., Berson, D.M., Foster, R.G. and Yau, K. W., Diminished pupillary light reflex at high irradiances in melanopsin knockout mice, Science, 299 (2003)

45 Circadian Hattar, S., Lucas, R.J., Mrosovsky, N., Thompson, S., Douglas, R.H., Hankins, M.W., Lem, J., Biel, M., Hofmann, F., Foster, R.G. & Yau, K.W. Melanopsin and rod-cone photoreceptive systems account for all major accessory visual functions in mice. Nature, (2003)

46 Non-rod, non-cone photoreception in the vertebrate eye A novel ocular photoreceptor? What is the nature of the novel photopigment? Which retinal neurones are photosensitive? What about melanopsin? Is melanopsin the circadian photopigment?

47 Gene ablation studies tell you that a gene is/is not important but such studies do not tell you the function of the gene!

48 The case for melanopsin as a photopigment is not yet settled. Functional biochemical data is incomplete.

49 The case for melanopsin as a photopigment is not yet settled. Functional biochemical data is incomplete. The structure of melanopsin does not resemble the known photosensory opsins.

50 The case for melanopsin as a photopigment is not yet settled. Functional biochemical data is incomplete. The structure of melanopsin does not resemble the known photosensory opsins. Melanopsin is expressed outside the photosensory ganlion cells of mice.

51 There is a complex network of directly light sensitive RGCs that provide light information to the circadian system. Calcium is part of the light signalling pathway. Melanopsin is a critical element for the photosensitive RGCs But if melanopsin is a photosensory pigment it is like no other.

52 How can an understanding of mechanisms of the photic input to the circadian system help us?

53 Need to establish whether abnormal light exposure is a risk factor for leukaemia and other forms of cancer

54 Need to establish whether abnormal light exposure is a risk factor for leukaemia and other forms of cancer Light treatments could provide new ways to manipulate the cell cycle and cellular proliferation. Will different light treatments or the pharmacological replacement of light alter tumour progression in vivo?

55 Need to establish whether abnormal light exposure is a risk factor for leukaemia and other forms of cancer Light treatments could provide new ways to manipulate the cell cycle and cellular proliferation. Will different light treatments or the pharmacological replacement of light alter tumour progression in vivo? Inform approaches of light hygiene for all age groups. What is the most appropriate light exposure to mitigate some of the problems of abnormal light exposure in our 24/7 society?

56 Acknowledgements Imperial Mark Hankins Robert Lucas James Bellingham Daniela Lupi Marta Muñoz Stuart Peirson Joanne Appleford Jason Butler Melanie Freedman Paraskevi Moutsaki Alistair Philp Ma ayan Semo Stewart Thompson Aaron Jenkins World Wim DeGrip Nicholas Mrosovsky Ron Douglas Ignacio Provencio Glen Jeffrey David Whitmore King Wai Yau