Regulation of alternative VEGF-A mRNA splicing is a therapeutic target for analgesia

Vascular endothelial growth factor-A (VEGF-A) is best known as a key regulator of the formation of new blood vessels. Neutralization of VEGF-A with anti-VEGF therapy e.g. bevacizumab, can be painful, and this is hypothesized to result from a loss of VEGF-A-mediated neuroprotection. The multiple vegf-a gene products consist of two alternatively spliced families, typified by VEGF-A₁₆₅a and VEGF-A₁₆₅b (both contain 165 amino acids), both of which are neuroprotective. Under pathological conditions, such as in inflammation and cancer, the pro-angiogenic VEGF-A₁₆₅a is upregulated and predominates over the VEGF-A₁₆₅b isoform.

We show here that in rats and mice VEGF-A₁₆₅a and VEGF-A₁₆₅b have opposing effects on pain, and that blocking the proximal splicing event – leading to the preferential expression of VEGF-A₁₆₅b over VEGF₁₆₅a – prevents pain in vivo. VEGF-A₁₆₅a sensitizes peripheral nociceptive neurons through actions on VEGFR2 and a TRPV1-dependent mechanism, thus enhancing nociceptive signaling. VEGF-A₁₆₅b blocks the effect of VEGF-A₁₆₅a.

After nerve injury, the endogenous balance of VEGF-A isoforms switches to greater expression of VEGF-A_xxxa compared to VEGF-A_xxxb, through an SRPK1-dependent pre-mRNA splicing mechanism. Pharmacological inhibition of SRPK1 after traumatic nerve injury selectively reduced VEGF-A_xxxa expression and reversed associated neuropathic pain. Exogenous VEGF-A₁₆₅b also ameliorated neuropathic pain.

We conclude that the relative levels of alternatively spliced VEGF-A isoforms are critical for pain modulation under both normal conditions and in sensory neuropathy. Altering VEGF-A_xxxa/VEGF-A_xxxb balance by targeting alternative RNA splicing may be a new analgesic strategy.

•

The different vegf-a splice variants, VEGF-A₁₆₅a and VEGF-A₁₆₅b have pro- and anti-nociceptive actions respectively.

•

Pro-nociceptive actions of VEGF-A₁₆₅a are dependent on TRPV1.

•

Alternative pre-mRNA splicing underpins peripheral sensitization by VEGF-A isoforms in normal and neuropathic animals.

VEGF-A165b is an endogenous neuroprotective splice isoform of vascular endothelial growth factor A in vivo and in vitro

Vascular endothelial growth factor (VEGF) A is generated as two isoform families by alternative RNA splicing, represented by VEGF-A165a and VEGF-A165b. These isoforms have opposing actions on vascular permeability, angiogenesis, and vasodilatation. The proangiogenic VEGF-A165a isoform is neuroprotective in hippocampal, dorsal root ganglia, and retinal neurons, but its propermeability, vasodilatatory, and angiogenic properties limit its therapeutic usefulness. In contrast, a neuroprotective effect of endogenous VEGF-A165b on neurons would be advantageous for neurodegenerative pathologies. Endogenous expression of human and rat VEGF-A165b was detected in hippocampal and cortical neurons. VEGF-A165b formed a significant proportion of total VEGF-A in rat brain. Recombinant human VEGF-A165b exerted neuroprotective effects in response to multiple insults, including glutamatergic excitotoxicity in hippocampal neurons, chemotherapy-induced cytotoxicity of dorsal root ganglion neurons, and retinal ganglion cells (RGCs) in rat retinal ischemia-reperfusion injury in vivo. Neuroprotection was dependent on VEGFR2 and MEK1/2 activation but not on p38 or phosphatidylinositol 3-kinase activation. Recombinant human VEGF-A165b is a neuroprotective agent that effectively protects both peripheral and central neurons in vivo and in vitro through VEGFR2, MEK1/2, and inhibition of caspase-3 induction. VEGF-A165b may be therapeutically useful for pathologies that involve neuronal damage, including hippocampal neurodegeneration, glaucoma diabetic retinopathy, and peripheral neuropathy. The endogenous nature of VEGF-A165b expression suggests that non-isoform-specific inhibition of VEGF-A (for antiangiogenic reasons) may be damaging to retinal and sensory neurons.

Influence of active recovery on professional rugby union player's ability to harness postactivation potentiation

AIM

After postactivation potentiation (PAP) has been induced, current research recommends that, on average, an 8 minute passive recovery period is applied before engaging in subsequent dynamic exercise. However, given the importance of maximizing time usage during the warm-up of elite athletes, it is likely that further exercise would be incorporated into this time frame. This study aimed to examine the effects of passive and active recovery on the ability to utilize PAP.

METHODS

In a randomised and counter balanced design, 36 professional rugby union players completed two experimental trials involving a baseline countermovement jump (CMJ), followed by a PAP stimulus (3 x 3 repetitions at 87% of 1-RM back squat) and CMJ retesting after 8 minutes of passive or active recovery. The active recovery involved subjects performing ballistic bench throws (1 x 3 repetitions at 30% 1-RM bench press) 4 minutes after the lower body PAP stimulus. Data presented as mean±SD.

RESULTS

Baseline peak power output (PPO) was not different between conditions (P=0.61). CMJ PPO increased from baseline under both conditions, however the delta (mean±SD; passive +161±127 vs. active +116±44 W; P=0.03) and % change (passive 3.3±2.8 vs. active 2.3±0.9 %; P=0.03) in PPO was greater after the passive recovery, when compared to the active recovery.

CONCLUSION

In conclusion, the passive and active recovery periods both led to increases in lower-body PPO, nevertheless, the passive recovery elicited the greatest performance changes. However, the active recovery is a more practical option for athletes, as it maximizes time usage during warm-up.

Ovarian VEGF(165)b expression regulates follicular development, corpus luteum function and fertility

Angiogenesis and vascular regression are critical for the female ovulatory cycle. They enable progression and regression of follicular development, and corpora lutea formation and regression. Angiogenesis in the ovary occurs under the control of the vascular endothelial growth factor-A (VEGFA) family of proteins, which are generated as both pro-(VEGF₁₆₅) and anti(VEGF₁₆₅b)-angiogenic isoforms by alternative splicing. To determine the role of the VEGF₁₆₅b isoforms in the ovulatory cycle, we measured VEGF₁₆₅b expression in marmoset ovaries by immunohistochemistry and ELISA, and used transgenic mice over-expressing VEGF₁₆₅b in the ovary. VEGF₁₆₅b was expressed in the marmoset ovaries in granulosa cells and theca, and the balance of VEGF₁₆₅b:VEGF₁₆₅ was regulated during luteogenesis. Mice over-expressing VEGF₁₆₅b in the ovary were less fertile than wild-type littermates, had reduced secondary and tertiary follicles after mating, increased atretic follicles, fewer corpora lutea and generated fewer embryos in the oviduct after mating, and these were more likely not to retain the corona radiata. These results indicate that the balance of VEGFA isoforms controls follicle progression and luteogenesis, and that control of isoform expression may regulate fertility in mammals, including in primates.

Overexpression of VEGF165b in podocytes reduces glomerular permeability

The observation that therapeutic agents targeting vascular endothelial growth factor-A (VEGF-A) associate with renal toxicity suggests that VEGF plays a role in the maintenance of the glomerular filtration barrier. Alternative mRNA splicing produces the VEGF(xxx)b family, which consists of antiangiogenic peptides that reduce permeability and inhibit tumor growth; the contribution of these peptides to normal glomerular function is unknown. Here, we established and characterized heterozygous and homozygous transgenic mice that overexpress VEGF(165)b specifically in podocytes. We confirmed excess production of glomerular VEGF(165)b by reverse transcriptase-PCR, immunohistochemistry, and ELISA in both heterozygous and homozygous animals. Macroscopically, the mice seemed normal up to 18 months of age, unlike the phenotype of transgenic podocyte-specific VEGF(164)-overexpressing mice. Animals overexpressing VEGF(165)b, however, had a significantly reduced normalized glomerular ultrafiltration fraction with accompanying changes in ultrastructure of the glomerular filtration barrier on the vascular side of the glomerular basement membrane. These data highlight the contrasting properties of VEGF splice variants and their impact on glomerular function and phenotype.

Mammary alveolar development during lactation is inhibited by the endogenous antiangiogenic growth factor isoform, VEGF165b

Extensive tissue remodeling occurs in breast tissue during pregnancy, resulting in growth and development of the mammary gland associated with extensive vascular remodeling, which is thought to be dependent on vascular endothelial growth factor (VEGF). We show here that the endogenous antiangiogenic splice isoform of VEGF, VEGF(165)b, is normally expressed in nonlactating human and mouse breast, and is down-regulated in WT mice during lactation. To demonstrate the physiological role of VEGF(165)b in mammary tissue, we generated transgenic (TG) mice expressing VEGF(165)b, under the control of the mouse mammary tumor virus (MMTV) enhancer/promoter. These mice increase expression of VEGF(165)b in mammary tissue during mammary development. The offspring of TG mothers, but not TG fathers, die shortly after birth. The female TG mice have fewer blood vessels, less blood in the mammary tissue, and impaired alveolar coverage of the fat pad, and do not produce sufficient milk for nourishment of their pups. These findings demonstrate that endogenous overexpression of VEGF(165)b in the mammary gland inhibits physiological angiogenesis and that the regulation of the balance of VEGF isoforms is a requirement for mammary alveolar development and milk production. This study provides the first evidence for the role of endogenous antiangiogenic VEGF isoforms in normal physiology--their down-regulation is required for effective milk production.

The next phase of healthcare improvement: what can we learn from social movements?

To date, improvement in health care has relied mainly on a "top down" programme by programme approach to service change and development. This has spawned a multitude of different and often impressive improvement schemes and activities. We question whether what has been happening will be sufficient to achieve the desired scale of change within the time scales set. Is it a case of "more of the same" or are there new and different approaches that might now be usefully implemented? Evidence from the social sciences suggests that other perspectives may help to recast large scale organisational change efforts in a new light and offer a different, though complementary, approach to improvement thinking and practice. Particularly prominent is the recognition that such large scale change in organisations relies not only on the "external drivers" but on the ability to connect with and mobilise people's own "internal" energies and drivers for change, thus creating a "bottom up" locally led "grass roots" movement for improvement and change.

Germline INI1 mutation in a patient with a central nervous system atypical teratoid tumor and renal rhabdoid tumor

We describe a four-month-old child who presented with an atypical teratoid/rhabdoid tumor of the brain and subsequently developed a renal rhabdoid tumor. Distinct histologic features, immunophenotypic profiles, and deletions of chromosome 22 were supportive of two primary tumors. An identical mutation in exon 7 of the INI1 rhabdoid tumor suppressor gene was identified in both tumors, as well as in normal kidney tissue. We propose that this germline INI1 mutation predisposed the child to the development of both malignancies. These findings lend support to the hypothesis that rhabdoid tumors in all sites have a common genetic etiology.

Stroke in young adults

Strokes in young adults are uncommon and often a diagnostic challenge. A retrospective study of strokes due to intracerebral hemorrhage, subarachnoid hemorrhage, or cerebral infarction was undertaken. We reviewed the medical records of 113 young patients aged 15-45 years who were admitted to the Medical Center Hospital of Vermont with a diagnosis of stroke between 1982 and 1987. This group comprised 8.5% of patients of all ages admitted for stroke, 2.3 times the proportion observed in the National Survey of Stroke. Nontraumatic intracerebral hemorrhage was diagnosed in 46 young patients (41%); the main causes included aneurysms, arteriovenous malformations, hypertension, and tumors. Subarachnoid hemorrhage was found in 19 young patients (17%); the majority were due to aneurysms. The remaining 48 young patients (42%) had cerebral infarction, the majority due to cardiogenic emboli and premature atherosclerosis. Mitral valve prolapse, the use of oral contraceptives, alcohol drinking, and migraine were infrequent sole causes of cerebral infarction in the absence of other risk factors. The case-fatality rate for this group of young patients with stroke was 20.4% compared with 23.9% for the National Survey of Stroke. Young adults with stroke deserve an extensive but tailored evaluation, which should include angiography and echocardiography.

Chronic segmental spinal muscular atrophy of upper extremities in identical twins

We present the 1st report of chronic segmental spinal muscular atrophy confined to the upper extremities in identical male twins. This occurrence in identical twins, together with reports of siblings and parent-child pairs of a disorder phenotypically similar to the more common sporadic form in the literature, suggests a genetic etiology in some cases.