Growth hormone as a neuronal rescue factor during recovery from CNS injury

• Published in: Neuroscience Vol. 104; no. 3; pp. 677 - 687
• Main Authors: Scheepens, A, Sirimanne, E.S, Breier, B.H, Clark, R.G, Gluckman, P.D, Williams, C.E
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.01.2001; Elsevier
• Subjects: Animals; Apoptosis - drug effects; Apoptosis - physiology; Biological and medical sciences; brain; Brain - drug effects; Brain - metabolism; Brain - physiopathology; Brain Injuries - drug therapy; Brain Injuries - metabolism; Brain Injuries - physiopathology; Carrier Proteins - pharmacology; Cell Count; Cell Survival - drug effects; Cell Survival - physiology; Female; growth factor; Growth Hormone - metabolism; Growth Hormone - pharmacology; Hypoxia-Ischemia, Brain - drug therapy; Hypoxia-Ischemia, Brain - metabolism; Hypoxia-Ischemia, Brain - physiopathology; Immunohistochemistry; ischaemia; Male; Medical sciences; Nerve Growth Factors - pharmacology; Neuroglia - cytology; Neuroglia - drug effects; Neuroglia - metabolism; neuron; Neurons - cytology; Neurons - drug effects; Neurons - metabolism; Neuropharmacology; Neuroprotective agent; Neuroprotective Agents - pharmacology; Pharmacology. Drug treatments; Rats; Rats, Wistar; Recombinant Proteins - pharmacology; Recovery of Function - drug effects; Recovery of Function - physiology; ABC, avidin–biotin–peroxidase complex; GHR/BP, growth hormone receptor/binding protein; ECM, extracellular matrix; neuron; ED, estimated displacement; KPBS, potassium phosphate-buffered saline; PBS, phosphate-buffered saline; bGH, bovine growth hormone; IGFBP, insulin-like growth factor binding protein; RT, room temperature; LI, -like immunoreactivity; BSA, bovine serum albumin; DAB, 3,3′-diaminobenzidine; LHS, left hand side; brain; GH, growth hormone; IgG, immunoglobulin class G; NGS, normal goat serum; growth factor; HI, hypoxic–ischaemia; IGF-I, II, insulin-like growth factor-1, 2; rrGH, recombinant rat growth hormone; ischaemia; GHR, growth hormone receptor; RHS, right hand side; CSF, cerebrospinal fluid; Nervous system diseases; Rat; Rodentia; Somatotropin hormone; Cardiovascular disease; Neuroprotective agent; Cerebral disorder; Vascular disease; Vertebrata; Experimental disease; Mammalia; Adenohypophyseal hormone; Ischemia; Animal; Central nervous system disease; Cerebrovascular disease; Brain (vertebrata)
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/S0306-4522(01)00109-9

There is growing evidence to suggest that growth hormone plays a role in the growth and development of the CNS. Specifically, growth hormone has been implicated in promoting brain growth, myelination, neuronal arborisation, glial differentiation and cognitive function. Here we investigate if growth hormone has a role in the recovery from an unilateral hypoxic–ischaemic brain injury. Using moderate (15 min hypoxia) and severe (60 min hypoxia) models of hypoxic–ischaemia in juvenile rats and standard immunohistochemical techniques, we found intense growth hormone-like immunoreactivity present within regions of cell loss by 3 days ( P<0.05). Growth hormone-like immunoreactivity was observed on injured neurones, myelinated axons, glial cells within and surrounding infarcted tissue and on the choroid plexus plus ependymal cells within the injured hemisphere. The pattern of immunoreactivity suggests that (a) growth hormone (or a growth hormone-like substance) is transported via the cerebrospinal fluid and (b) that growth hormone (or a growth hormone-like substance) is acting in a neurotrophic manner specifically targeted to injured neurones and glia. To test this hypothesis we treated a moderate hypoxic–ischaemic brain injury with 20 μg of rat growth hormone by intracerebroventricular infusion starting 2 h after injury ( n=12/group). After 3 days the animals were killed and the extent of neuronal loss quantified. Growth hormone treatment reduced neuronal loss in the frontoparietal cortex ( P<0.001), hippocampus ( P<0.01) and dorsolateral thalamus ( P<0.01) but not in the striatum. This spatial distribution of the neuroprotection conveyed by growth hormone correlates with the spatial distribution of the constitutive neural growth hormone receptor, but not with the neuroprotection offered by insulin-like growth factor-I treatment in this model. These results suggest that some of the neuroprotective effects of growth hormone are mediated directly through the growth hormone receptor and do not involve insulin-like growth factor-I induction. In summary, we have found that a growth hormone-like factor increased in the brain in the days after injury. In addition, treatment with growth hormone soon after an hypoxic–ischaemic injury reduced the extent of neuronal loss. These results further suggest that a neural growth hormone axis is activated during recovery from injury and that this may act to restrict the extent of neuronal death.