Valproate Reduces Delayed Brain Injury in a Rat Model of Subarachnoid Hemorrhage

Identification of key genes and immune infiltration in peripheral blood biomarker analysis of delayed cerebral ischemia: Valproic acid as a potential therapeutic drug

BACKGROUND

Delayed cerebral ischemia (DCI) is a common and serious complication of subarachnoid hemorrhage (SAH). Its pathogenesis is not fully understood. Here, we developed a predictive model based on peripheral blood biomarkers and validated the model using several bioinformatic multi-analysis methods.

METHODS

Six datasets were obtained from the GEO database. Characteristic genes were screened using weighted correlation network analysis (WGCNA) and differentially expressed genes. Three machine learning algorithms, elastic networks-LASSO, support vector machines (SVM-RFE) and random forests (RF), were also used to construct diagnostic prediction models for key genes. To further evaluate the performance and predictive value of the diagnostic models, nomogram model were constructed, and the clinical value of the models was assessed using Decision Curve Analysis (DCA), Area Under the Check Curve (AUC), Clinical Impact Curve (CIC), and validated in the mouse single-cell RNA-seq dataset. Mendelian randomization(MR) analysis explored the causal relationship between SAH and stroke, and the intermediate influencing factors. We validated this by retrospectively analyzing the qPCR levels of the most relevant genes in SAH and SAH-DCI patients. This experiment demonstrated a statistically significant difference between SAH and SAH-DCI and normal group controls. Finally, potential small molecule compounds interacting with the selected features were screened from the Comparative Toxicogenomics Database (CTD).

RESULTS

The fGSEA results showed that activation of Toll-like receptor signaling and leukocyte transendothelial cell migration pathways were positively correlated with the DCI phenotype, whereas cytokine signaling pathways and natural killer cell-mediated cytotoxicity were negatively correlated. Consensus feature selection of DEG genes using WGCNA and three machine learning algorithms resulted in the identification of six genes (SPOCK2, TRRAP, CIB1, BCL11B, PDZD8 and LAT), which were used to predict DCI diagnosis with high accuracy. Three external datasets and the mouse single-cell dataset showed high accuracy of the diagnostic model, in addition to high performance and predictive value of the diagnostic model in DCA and CIC. MR analysis looked at stroke after SAH independent of SAH, but associated with multiple intermediate factors including Hypertensive diseases, Total triglycerides levels in medium HDL and Platelet count. qPCR confirmed that significant differences in DCI signature genes were observed between the SAH and SAH-DCI groups. Finally, valproic acid became a potential therapeutic agent for DCI based on the results of target prediction and molecular docking of the characterized genes.

CONCLUSION

This diagnostic model can identify SAH patients at high risk for DCI and may provide potential mechanisms and therapeutic targets for DCI. Valproic acid may be an important future drug for the treatment of DCI.

Amarogentin has protective effects against sepsis-induced brain injury via modulating the AMPK/SIRT1/NF-κB pathway

Amarogentin (AMA), a secoiridoid glycoside that is mainly derived from SwertiaandGentiana roots, has been confirmed to exhibit antioxidative, tumor-suppressive and anti-diabetic properties. This research intends to investigate the protective effect of AMA against sepsis-induced brain injury and its mechanism. NSC-34 and HT22 cells were treated with lipopolysaccharide (LPS) to induce an in-vitro sepsis model and then treated with varying concentrations (1, 5, 10 µM) of AMA. Cell proliferation and apoptosis were evaluated. The intensity of inflammation and oxidative stress were assessed by different methods. The AMPK/SIRT1/NF-κB pathway expression was determined by WB. An in-vitro sepsis model was set up with cecal ligation and puncture (CLP) in adult C57/BL6J mice, and different concentrations (25, 50, 100 mg/kg) of AMA were applied for treatment. Neurological function was evaluated using the modified neurological severity scores (mNSS), and the brain tissue damage was measured using hematoxylin-eosin (H&E) staining and Nissl staining. Tissue apoptosis was tested using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Then, the AMPK inhibitor Compound C (CC) was administered to confirm AMA-mediated mechanism. Our finding illustrated that AMA mitigated LPS-induced neuronal damage, inflammation and oxidative stress, activated the AMPK/SIRT1 pathway and choked NF-κB phosphorylation. Furthermore, AMA improved neurological functions of sepsis mice by reliving neuroinflammation and oxidative stress. Inhibition of AMPK attenuated the protective effect of AMA on neurons or the mice's brain tissues. In conclusion, AMA protected against sepsis-induced brain injury by modulating the AMPK/SIRT1/NF-κB pathway.

Spontaneous subarachnoid haemorrhage

Subarachnoid haemorrhage (SAH) is the third most common subtype of stroke. Incidence has decreased over past decades, possibly in part related to lifestyle changes such as smoking cessation and management of hypertension. Approximately a quarter of patients with SAH die before hospital admission; overall outcomes are improved in those admitted to hospital, but with elevated risk of long-term neuropsychiatric sequelae such as depression. The disease continues to have a major public health impact as the mean age of onset is in the mid-fifties, leading to many years of reduced quality of life. The clinical presentation varies, but severe, sudden onset of headache is the most common symptom, variably associated with meningismus, transient or prolonged unconsciousness, and focal neurological deficits including cranial nerve palsies and paresis. Diagnosis is made by CT scan of the head possibly followed by lumbar puncture. Aneurysms are commonly the underlying vascular cause of spontaneous SAH and are diagnosed by angiography. Emergent therapeutic interventions are focused on decreasing the risk of rebleeding (ie, preventing hypertension and correcting coagulopathies) and, most crucially, early aneurysm treatment using coil embolisation or clipping. Management of the disease is best delivered in specialised intensive care units and high-volume centres by a multidisciplinary team. Increasingly, early brain injury presenting as global cerebral oedema is recognised as a potential treatment target but, currently, disease management is largely focused on addressing secondary complications such as hydrocephalus, delayed cerebral ischaemia related to microvascular dysfunction and large vessel vasospasm, and medical complications such as stunned myocardium and hospital acquired infections.

Cortical Spreading Depolarizations in Aneurysmal Subarachnoid Hemorrhage: An Overview of Current Knowledge and Future Perspectives

Despite significant advances in the management of aneurysmal subarachnoid hemorrhage (SAH), morbidity and mortality remain devastating particularly for high-grade SAH. Poor functional outcome usually results from delayed cerebral ischemia (DCI). The pathogenesis of DCI during aneurysmal SAH has historically been attributed to cerebral vasospasm, but spreading depolarizations (SDs) are now considered to play a central role in DCI. During SAH, SDs may produce an inverse hemodynamic response leading to spreading ischemia. Several animal models have contributed to a better understanding of the pathogenesis of SDs during aneurysmal SAH and provided new therapeutic approaches including N-methyl-D-aspartate receptor antagonists and phosphodiesterase inhibitors. Herein we review the current knowledge in the field of SDs' pathogenesis and we detail the key experimental and clinical studies that have opened interesting new therapeutic approaches to prevent DCI in aneurysmal SAH.

Local Application of Magnesium Sulfate Solution Suppressed Cortical Spreading Ischemia and Reduced Brain Damage in a Rat Subarachnoid Hemorrhage-Mimicking Model

OBJECTIVE

Cortical spreading depolarization (CSD), cortical spreading ischemia (CSI), and early brain injury are involved in the occurrence of delayed brain ischemia after subarachnoid hemorrhage (SAH). We tested whether local application of magnesium (Mg) sulfate solution suppressed CSD and CSI, and decreased brain damage in a rat SAH-mimicking model.

METHODS

Nitric oxide synthase inhibitor L-NG-nitroarginine methyl ester (L-NAME) and high concentration potassium solution were topically applied to simulate the environment after SAH. We irrigated the parietal cortex with artificial cerebrospinal fluid (ACSF), containing L-NAME (1 mM), K⁺ (35 mM), and Mg²⁺ (5 mM). Forty-five rats were divided into 3 groups: sham surgery (sham group), L-NAME + [K⁺]_ACSF (control group), and L-NAME + [K⁺]_ACSF + [Mg²⁺] (Mg group). CSD was induced by topical application with 1 M KCl solution in 3 groups. The effects of Mg administration on CSD and cerebral blood flow were evaluated. Histological brain tissue damage, body weight, and neurological score were assessed at 2 days after insult.

RESULTS

Mg solution significantly shortened the total depolarization time, and reduced CSI, histological brain damage, and brain edema compared with those of the control group (P < 0.05). Body weight loss was significantly suppressed in the Mg group (P < 0.05), but neurological score did not improve.

CONCLUSIONS

Local application of Mg suppressed CSI and reduced brain damage in a rat SAH-mimicking model. Mg irrigation therapy may be beneficial to suppress brain damage due to CSI after SAH.

Pathophysiology of Delayed Cerebral Ischemia After Subarachnoid Hemorrhage: A Review

Delayed cerebral ischemia is a major predictor of poor outcomes in patients who suffer subarachnoid hemorrhage. Treatment options are limited and often ineffective despite many years of investigation and clinical trials. Modern advances in basic science have produced a much more complex, multifactorial framework in which delayed cerebral ischemia is better understood and novel treatments can be developed. Leveraging this knowledge to improve outcomes, however, depends on a holistic understanding of the disease process. We conducted a review of the literature to analyze the current state of investigation into delayed cerebral ischemia with emphasis on the major themes that have emerged over the past decades. Specifically, we discuss microcirculatory dysfunction, glymphatic impairment, inflammation, and neuroelectric disruption as pathological factors in addition to the canonical focus on cerebral vasospasm. This review intends to give clinicians and researchers a summary of the foundations of delayed cerebral ischemia pathophysiology while also underscoring the interactions and interdependencies between pathological factors. Through this overview, we also highlight the advances in translational studies and potential future therapeutic opportunities.

Valproic Acid Reduces Vasospasm through Modulation of Akt Phosphorylation and Attenuates Neuronal Apoptosis in Subarachnoid Hemorrhage Rats

Aneurysmal subarachnoid hemorrhage (SAH) is a devastating emergent event associated with high mortality and morbidity. Survivors usually experience functional neurological sequelae caused by vasospasm-related delayed ischemia. In this study, male Sprague-Dawley rats were randomly assigned to five groups: sham (non-SAH) group, SAH group, and three groups with SAH treated with different doses of valproic acid (VPA) (10, 20, 40 mg/kg, once-daily, for 7 days). The severity of vasospasm was determined by the ratio of cross-sectional areas to intima-media thickness of the basilar arteries (BA) on the seventh day after SAH. The BA showed decreased expression of phospho-Akt proteins. The dentate gyrus showed increased expression of cleaved caspase-3 and Bax proteins and decreased expression of Bcl-2, phospho-ERK 1/2, phospho-Akt and acetyl-histone H3 proteins. The incidence of SAH-induced vasospasm was significantly lower in the SAH group treated with VPA 40 mg/kg (p < 0.001). Moreover, all groups treated with VPA showed reversal of the above-mentioned protein expression in BA and the dentate gyrus. Treatment with VPA upregulated histone H3 acetylation and conferred anti-vasospastic and neuro-protective effects by enhancing Akt and/or ERK phosphorylation. This study demonstrated that VPA could alleviate delayed cerebral vasospasm induced neuro-apoptosis after SAH.

Melanocortin 1 receptor attenuates early brain injury following subarachnoid hemorrhage by controlling mitochondrial metabolism via AMPK/SIRT1/PGC-1α pathway in rats

Mitochondria-mediated oxidative stress and apoptosis contribute greatly to early brain injury (EBI) following subarachnoid hemorrhage (SAH). This study hypothesized that activation of melanocortin 1 receptor (MC1R), using BMS-470539, attenuates EBI by controlling mitochondrial metabolism after SAH. Methods: We utilized BMS-470539, MSG-606, selisistat, and PGC-1α to verify the neuroprotective effects of MC1R. We evaluated short- and long-term neurobehavior after SAH. Western blotting, immunofluorescence, and Golgi staining techniques were performed to assess changes in protein levels. Results: The results of western blotting suggested that the expression of SIRT1 and PGC-1α were increased, reaching their peaks at 24 h following SAH. Moreover, BMS-470539 treatment notably attenuated neurological deficits, and also reduced long-term spatial learning and memory impairments caused by SAH. The underlying neuroprotective mechanisms of the BMS-470539/MC1R system were mediated through the suppression of oxidative stress, apoptosis, and mitochondrial fission by increasing the levels of SIRT1, PGC-1α, UCP2, SOD, GPx, Bcl-2, cyto-Drp1, and ATP, while decreasing the levels of cleaved caspase-3, Bax, mito-Drp1, ROS, GSH/GSSG, and NADPH/NADP+ ratios. The neuroprotective effects of the BMS-470539/MC1R system were significantly abolished by MSG-606, selisistat, and PGC-1α siRNA. Conclusions: The activation of MC1R with BMS-470539 significantly attenuated EBI after SAH by suppressing the oxidative stress, apoptosis, and mitochondrial fission through the AMPK/SIRT1/PGC-1α signaling pathway.

Valproate Sodium Protects Blood Brain Barrier Integrity in Intracerebral Hemorrhage Mice

Valproate sodium (VPA) is a traditional antiepileptic drug with a neuroprotective role in cerebrovascular disease. After intracerebral hemorrhage (ICH), mechanical compression by hematoma, neuroinflammation, oxidative stress, and cytotoxicity of hematoma lysates caused the destruction of the blood brain barrier (BBB). Targeting BBB is a major therapeutic method for patients with ICH. The purpose of the present study was to explore the role of VPA in preserving BBB integrity in the ICH model and investigate the underlying molecular mechanisms. One hundred and thirty-six adult male CD1 mice were randomly divided into five groups in the study. Mice subjected to ICH were administered intraperitoneally with VPA at 3, 24, and 48 h post-ICH, respectively. Neurobehavioral assessments, BBB permeability, Evans blue fluorescence, hematoma volume, and protein expression were evaluated. The administration of VPA reduced BBB permeability and improved the neurobehavior significantly post-ICH. VPA administration significantly decreased the expression of phosphorylated nuclear factor-kappa B (p-NFκB), matrix metalloproteinases 9 (MMP9), tumor necrosis factorα (TNFα), and interleukin-6 (IL-6), while it enhanced the expression of claudin 5 and occludin in the brain. In conclusion, VPA administration maintained the integrity of BBB after experimental ICH, thus reducing brain edema and improving the neurological outcomes. Therefore, VPA administration might be a new therapeutic method to protect BBB integrity for patients with ICH.

Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage in Patients With a History of Migraine

Background and Purpose:

Delayed cerebral ischemia (DCI) is a major contributor to the high morbidity in patients with aneurysmal subarachnoid hemorrhage (aSAH). Spreading depolarizations may play a role in DCI pathophysiology. Because patients with migraine are probably more susceptible to spreading depolarizations, we investigated whether patients with aneurysmal subarachnoid hemorrhage with migraine are at increased risk for DCI.

Methods:

We included patients with aneurysmal subarachnoid hemorrhage from 3 hospitals in the Netherlands. We assessed lifetime migraine history with a short screener. DCI was defined as neurological deterioration lasting >1 hour not attributable to other causes by diagnostic work-up. Adjustments were made for possible confounders in multivariable Cox regression analyses and adjusted hazard ratios (aHR) were calculated. We assessed the interaction effects of age and sex.

Results:

We included 582 patients (mean age 57 years, 71% women) mostly with mild to moderate aneurysmal subarachnoid hemorrhage of whom 108 (19%) had a history of migraine (57 with aura). Patients with migraine were not at increased risk of developing DCI compared with patients without migraine (22% versus 24%, aHR, 0.89 [95% CI, 0.56–1.43]). Additionally, no increased risk was found in patients with migraine with possible aura (aHR, 0.74 [95% CI, 0.39–1.43]), in women (aHR, 0.88 [95% CI, 0.53–1.45], P interaction =0.859), or in young patients aged <50 years (aHR, 1.59 [95% CI, 0.72–3.49]), although numbers in these subgroups were limited. We found an interaction between migraine and age with an increased risk of DCI among young patients with migraine ( P interaction =0.075).

Conclusions:

Patients with migraine are in general not at increased risk of DCI. Future studies should focus in particular on young SAH patients, in whom there might be an association between migraine history and development of DCI.

Spreading Depolarizations and Subarachnoid Hemorrhage

Cortical spreading depolarizations (SD) are strongly associated with worse tissue injury and clinical outcomes in the setting of aneurysmal subarachnoid hemorrhage (SAH). Animal studies have suggested a causal relationship, and new therapies to target SDs are starting to be tested in clinical studies. A recent set of single-center randomized trials assessed the effect of the phosphodiesterase inhibitor cilostazol in patients with SAH. Cilostazol led to improved functional outcomes and SD-related metrics in treated patients through a putative mechanism of improved cerebral blood flow. Another promising therapeutic approach includes attempts to block SDs with, for example, the NMDA receptor antagonist ketamine. SDs have emerged not only as a therapeutic target but also as a potentially useful biomarker for brain injury following SAH. Additional clinical and preclinical experimental work is greatly needed to assess the generalizability of existing therapeutic trials and to better delineate the relationship between SDs, SAH, and functional outcome.

Delayed Cerebral Ischemia After Subarachnoid Hemorrhage: Experimental-Clinical Disconnect and the Unmet Need

BACKGROUND

Delayed cerebral ischemia (DCI) is among the most dreaded complications following aneurysmal subarachnoid hemorrhage (SAH). Despite advances in neurocritical care, DCI remains a significant cause of morbidity and mortality, prolonged intensive care unit and hospital stay, and high healthcare costs. Large artery vasospasm has classically been thought to lead to DCI. However, recent failure of clinical trials targeting vasospasm to improve outcomes has underscored the disconnect between large artery vasospasm and DCI. Therefore, interest has shifted onto other potential mechanisms such as microvascular dysfunction and spreading depolarizations. Animal models can be instrumental in dissecting pathophysiology, but clinical relevance can be difficult to establish.

METHODS

Here, we performed a systematic review of the literature on animal models of SAH, focusing specifically on DCI and neurological deficits.

RESULTS

We find that dog, rabbit and rodent models do not consistently lead to DCI, although some degree of delayed vascular dysfunction is common. Primate models reliably recapitulate delayed neurological deficits and ischemic brain injury; however, ethical issues and cost limit their translational utility.

CONCLUSIONS

To facilitate translation, clinically relevant animal models that reproduce the pathophysiology and cardinal features of DCI after SAH are urgently needed.

Activation of Melanocortin 1 Receptor Attenuates Early Brain Injury in a Rat Model of Subarachnoid Hemorrhage viathe Suppression of Neuroinflammation through AMPK/TBK1/NF-κB Pathway in Rats

Neuroinflammation plays a vital role in early brain injury (EBI) following subarachnoid hemorrhage (SAH). The hypothesis of this study was that activation of melanocortin 1 receptor (MC1R) with BMS-470539 attenuates EBI by suppression of neuroinflammation after SAH. We utilized BMS-470539, MSG-606, and MRT-68601 to verify the neuroprotective effects of MC1R. We evaluated brain water content, short-term and long-term neurobehavior after SAH. Western blotting and immunofluorescence staining were utilized to assess the changes of protein levels. The results of western blotting suggested that the expressions of MC1R, phosphorylated-adenosine monophosphate-activated protein kinase (p-AMPK), and phosphorylated-TANK binding kinase 1 (p-TBK1) were increased and reached their peak points at 24 h following SAH. Moreover, BMS-470539 treatment notably attenuated neurological deficits caused by SAH, and also notably improved long-term spatial learning and memory abilities after SAH. The underlying mechanisms of the neuroprotection of BMS-470539 involved the suppression of microglia activation, promotion of CD206+ microglia transformation and reduction of neutrophil infiltration by increasing the levels of p-AMPK and p-TBK1 while decreasing the levels of NF-κB, IL-1β, and TNFα. The neuroprotective effects of BMS-470539 were significantly abolished by MSG-606 and MRT-68601. The activation of MC1R with BMS-470539 notably attenuates EBI after SAH by suppression of microglial activation and neutrophil infiltration via the AMPK/TBK1/NF-κB signaling pathway.

Systematic review and meta-analysis of experimental studies evaluating the organ protective effects of histone deacetylase inhibitors

The clinical efficacy of organ protection interventions are limited by the redundancy of cellular activation mechanisms. Interventions that target epigenetic mechanisms overcome this by eliciting genome wide changes in transcription and signaling. We aimed to review preclinical studies evaluating the organ protection effects of histone deacetylase inhibitors (HDACi) with a view to informing the design of early phase clinical trials. A systematic literature search was performed. Methodological quality was assessed against prespecified criteria. The primary outcome was mortality, with secondary outcomes assessing mechanisms. Prespecified analyses evaluated the effects of likely moderators on heterogeneity. The analysis included 101 experimental studies in rodents (n = 92) and swine (n = 9), exposed to diverse injuries, including: ischemia (n = 72), infection (n = 7), and trauma (n = 22). There were a total of 448 comparisons due to the evaluation of multiple independent interventions within single studies. Sodium valproate (VPA) was the most commonly evaluated HDACi (50 studies, 203 comparisons). All of the studies were judged to have significant methodological limitations. HDACi reduced mortality in experimental models of organ injury (risk ratio = 0.52, 95% confidence interval 0.40-0.68, p < 0.001) without heterogeneity. HDACi administration resulted in myocardial, brain and kidney protection across diverse species and injuries that was attributable to increases in prosurvival cell signaling, and reductions in inflammation and programmed cell death. Heterogeneity in the analyses of secondary outcomes was explained by differences in species, type of injury, HDACi class (Class I better), drug (trichostatin better), and time of administration (at least 6 hours prior to injury better). These findings highlight a potential novel application for HDACi in clinical settings characterized by acute organ injury.

Early Inflammatory Response in the Brain and Anesthesia Recovery Time Evaluation After Experimental Subarachnoid Hemorrhage

The main objective was to evaluate, whether the subarachnoid hemorrhage (SAH)-associated early inflammatory response has focal or global character, i.e., whether areas distant to hematoma may be affected by an early inflammatory response. The second objective was to evaluate the association of anesthesia recovery time for basic reflexes/neurological functions with severity of SAH. SAH was induced in rats using an endovascular perforation model. Anesthesia recovery time was evaluated for pain reaction recovery time (spinal level), spontaneous ventilation recovery time (brain stem level), and consciousness recovery time (neocortical level). mRNA expressions of TNFα, IL-1β, IL-6, ICAM-1, and VCAM-1 in areas adjacent and distant to hematoma were evaluated between 2 and 8 h after SAH. Serum levels of TNFα, IL-1β, and IL-6 were assessed at 4 and 8 h after SAH. Anesthesia recovery time of all selected parameters was associated with severity of SAH. The consciousness recovery time test had the best predictive value, while the spontaneous ventilation recovery time test was able to bring information in the shortest time. The mRNA expressions of pro-inflammatory cytokines were significantly increased in severe SAH groups in both adjacent and distant areas. The inflammatory response in mild/moderate SAH groups was less strong, peaking at 4 h after SAH. Serum levels of pro-inflammatory cytokines were ambiguous. Anesthesia recovery time may be useful for bleeding severity prediction in the SAH model; however, further validation is needed. Severe subarachnoid hemorrhage is associated with the strong early inflammatory response, which has a global character, while mild subarachnoid hemorrhage is accompanied by a weaker inflammation.

Blixt F, Edvinsson L, Ansar S. Acute mitogen-activated protein kinase 1/2 inhibition improves functional recovery and vascular changes after ischaemic stroke in rat-monitored by 9.4 T magnetic resonance imaging

AIM

The aim was to evaluate the beneficial effect of early mitogen-activated protein kinase (MEK)1/2 inhibition administered at a clinical relevant time-point using the transient middle cerebral artery occlusion model and a dedicated rodent magnetic resonance imaging system (9.4T) to monitor cerebrovascular changes non-invasively for 2 weeks.

METHOD

Transient middle cerebral artery occlusion was induced in male rats for two hours followed by reperfusion. The specific MEK1/2 inhibitor U0126 was administered ip at 6 and 24 hours post-reperfusion. Neurological functions were evaluated by 6- and 28-point tests. 9.4 T magnetic resonance imaging was used to monitor morphological infarct changes at day 2, 8 and 14 after stroke and to evaluate cerebral perfusion at day 14. Immunohistochemistry evaluation of Ki67 was performed 14 days post-stroke.

RESULTS

U0126 improved long-term behavioural outcome and significantly reduced infarct size. In addition, cerebral perfusion in U0126-treated animals was improved compared to the vehicle group. Immunohistochemistry showed a significant increase in Ki67⁺ cells in U0126-treated animals compared to the vehicle group.

CONCLUSION

Early MEK1/2 inhibition improves long-term functional outcome, promotes recovery processes after stroke and most importantly provides a realistic time window for therapy.