Organ memory: a key principle for understanding the pathophysiology of hypertension and other non-communicable diseases

Effects of maternal PM2.5 exposure during pregnancy on cardiovascular maldevelopment in rat offspring

BACKGROUND

Epidemiological studies suggest a link between maternal exposure to PM2.5 during pregnancy and a higher incidence of fetal cardiovascular abnormalities. However, experimental data on the underlying mechanisms remain scarce.

OBJECTIVE

This study aims to explore the effects of maternal PM2.5 exposure during pregnancy on fetal cardiovascular maldevelopment in a rat model.

METHODS

Twenty-eight pregnant rats were divided into control and PM2.5-exposed groups according the exposure doses (N = 7 per group). Rats were administered with PM2.5 suspensions corresponding to 0, 2.6, 5.5, and 11 μg/d, respectively, during gestation. On gestational day 21, neonatal hearts were collected, and levels of cardiac transcription factors (Tbx2, Tbx20, Hand2 and Gata6), MMP9, TN-C, VEGF-A, NF-κB, apoptotic markers (Bax/Bcl-2 ratio), catalase (CAT), and lipid metabolism indicators were measured.

RESULTS

In the 11 μg/d group, the mRNA levels of Tbx2, Tbx20, Hand2, Gata6, MMP9, TN-C and VEGF-A, the protein levels of Tbx2, Hand2, and TN-C, and blood CAT activity were significantly reduced (P < 0.05). Conversely, NF-κB, Bax/Bcl-2, and serum markers of dyslipidemia (TC, TG, LDH, LDL-C/HDL-C) were significantly elevated (P < 0.05). Additionally, TN-C and Hand2 mRNA levels were reduced in the 2.6 μg/d group, and LDH level was increased in the 5.5 μg/d group (P < 0.05).

CONCLUSIONS

Maternal PM2.5 exposure during pregnancy is associated with fetal cardiovascular maldevelopments, possibly through the changes of cardiac transcription factors, vascular dysfunction, oxidative stress, apoptosis, and abnormalities of lipid metabolism.

Intermittent Fasting Sustainably Improves Glucose Tolerance in Normal Weight Male Mice Through Histone Hyperacetylation

To explore the mechanism by which intermittent fasting (IF) exerts prolonged effects after discontinuation, we examined mice that had been subjected to 4 cycles of fasting for 72 hours and ad libitum feeding for 96 hours per week (72hIF), followed by 4 weeks of ad libitum feeding, focusing on expression of genes for lipid metabolism in the skeletal muscle and histone acetylation in the promoter region. The 72hIF regimen resulted in metabolic remodeling, characterized by enhanced lipid utilization and mitochondrial activation in the muscle. This long-term IF (72hIF) caused stronger metabolic effects than alternate day fasting (24hIF) wherein fasting and refeeding are repeated every 24 hours. Upregulation of lipid oxidation genes and an increase in oxygen utilization were sustained even at 4 weeks after discontinuation of 72hIF, associated with histone hyperacetylation of the promoter region of uncoupling protein 3 (Ucp3) and carnitine palmitoyl transferase 1b (Cpt1b) genes. An increase in leucine owing to fasting-induced muscle degradation was suggested to lead to the histone acetylation. These findings support the previously unappreciated notion that sustainable promotion of histone acetylation in lipid oxidation genes of the muscle and adipose tissues during and after IF may contribute to sustained metabolic effects of IF.

The link between immunity and hypertension in the kidney and heart

Hypertension is the primary cause of cardiovascular disease, which is a leading killer worldwide. Despite the prevalence of this non-communicable disease, still between 90% and 95% of cases are of unknown or multivariate cause ("essential hypertension"). Current therapeutic options focus primarily on lowering blood pressure through decreasing peripheral resistance or reducing fluid volume, but fewer than half of hypertensive patients can reach blood pressure control. Hence, identifying unknown mechanisms causing essential hypertension and designing new treatment accordingly are critically needed for improving public health. In recent years, the immune system has been increasingly implicated in contributing to a plethora of cardiovascular diseases. Many studies have demonstrated the critical role of the immune system in the pathogenesis of hypertension, particularly through pro-inflammatory mechanisms within the kidney and heart, which, eventually, drive a myriad of renal and cardiovascular diseases. However, the precise mechanisms and potential therapeutic targets remain largely unknown. Therefore, identifying which immune players are contributing to local inflammation and characterizing pro-inflammatory molecules and mechanisms involved will provide promising new therapeutic targets that could lower blood pressure and prevent progression from hypertension into renal or cardiac dysfunction.

Activation of the intestinal tissue renin-angiotensin system by transient sodium loading in salt-sensitive rats

BACKGROUND

The renal tissue renin-angiotensin system is known to be activated by salt loading in salt-sensitive rats; however, the response in other organs remains unclear.

METHOD

Spontaneously hypertensive rats were subjected to normal tap water or transient high-salt-concentration water from 6 to 14 weeks of age and were thereafter given normal tap water. From 18 to 20 weeks of age, rats given water with a high salt concentration were treated with an angiotensin II type 1 receptor blocker, valsartan.

RESULTS

Sustained blood pressure elevation by transient salt loading coincided with a persistent decrease in the fecal sodium content and sustained excess of the circulating volume in spontaneously hypertensive rats. Administration of valsartan sustainably reduced the blood pressure and normalized the fecal sodium levels. Notably, transient salt loading persistently induced the intestinal tissue renin-angiotensin system and enhanced sodium transporter expression exclusively in the small intestine of salt-sensitive rats, suggesting the potential connection of intestinal sodium absorption to salt sensitivity.

CONCLUSION

These results reveal the previously unappreciated contribution of the intestinal tissue renin-angiotensin system to sodium homeostasis and blood pressure regulation in the pathophysiology of salt-sensitive hypertension.

DNA repair factor KAT5 prevents ischemic acute kidney injury through glomerular filtration regulation

The “preconditioning effect” in AKI is a phenomenon in which an episode of ischemia-reperfusion results in tolerance to subsequent ischemia-reperfusion injury. However, its relationship between DNA damage repair has not been elucidated. Here, we show the role of KAT5 in the preconditioning effect. Preconditioning attenuated DNA damage in proximal tubular cells with elevated KAT5 expression. Ischemia-reperfusion (IR) injuries were exacerbated, and preconditioning effect vanished in proximal tubular-cell-specific KAT5 knockout mice. Investigation of tubuloglomerular feedback (TGF) by MALDI-IMS and urinary adenosine revealed that preconditioning caused attenuated TGF at least in part via KAT5. In addition, K-Cl cotransporter 3 (KCC3) expression decreased in damaged proximal tubular cells, which may be involved in accelerated TGF following IR. Furthermore, KAT5 induced KCC3 expression by maintaining chromatin accessibility and binding to the KCC3 promoter. These results suggest a novel mechanism of the preconditioning effect mediated by the promotion of DNA repair and attenuation of TGF through KAT5.

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KAT5-mediated DNA damage repair acts against ischemia-reperfusion (IR) injuries

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K-Cl cotransporter3 (KCC3) expression is decreased in damaged proximal tubular cells

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Decreased KCC3 may lead to AKI via acceleration of tubuloglomerular feedback

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KAT5 induces KCC3 expression through an epigenetic mechanism

Transient Dexamethasone Loading Induces Prolonged Hyperglycemia in Male Mice With Histone Acetylation in Dpp-4 Promoter

Glucocorticoid causes hyperglycemia, which is common in patients with or without diabetes. Prolonged hyperglycemia can be experienced even after the discontinuation of glucocorticoid use. In the present study, we examined the time course of blood glucose level in hospital patients who received transient glucocorticoid treatment. In addition, the mechanism of prolonged hyperglycemia was investigated by using dexamethasone (Dexa)-treated mice and cultured cells. The blood glucose level in glucose tolerance tests, level of insulin and glucagon-like peptide 1 (GLP-1), and the activity of dipeptidyl peptidase 4 (DPP-4) were examined during and after Dexa loading in mice, with histone acetylation level of the promoter region. Mice showed prolonged hyperglycemia during and after transient Dexa loading accompanied by persistently lower blood GLP-1 level and higher activity of DPP-4. The expression level of Dpp-4 was increased in the mononuclear cells and the promoter region of Dpp-4 was hyperacetylated during and after the transient Dexa treatment. In vitro experiments also indicated development of histone hyperacetylation in the Dpp-4 promoter region during and after Dexa treatment. The upregulation of Dpp-4 in cultured cells was significantly inhibited by a histone acetyltransferase inhibitor. Moreover, the histone hyperacetylation induced by Dexa was reversible by treatment with a sirtuin histone deacetylase activator, nicotinamide mononucleotide. We identified persistent reduction in blood GLP-1 level with hyperglycemia during and after Dexa treatment in mice, associated with histone hyperacetylation of promoter region of Dpp-4. The results unveil a novel mechanism of glucocorticoid-induced hyperglycemia, and suggest therapeutic intervention through epigenetic modification of Dpp-4.

Pre-emptive medicine for hypertension and its prospects

Pre-emptive medicine is a novel medical concept proposed in Japan that aims to precisely predict the onset and progression of diseases and to provide therapeutic interventions during early stages, before symptoms appear. The concept of pre-emptive medicine considers the time-course of a disease in each individual and seeks medical interventions to prevent disease progression. Suitable and promising targets for pre-emptive medicine are non-communicable diseases, including hypertension. Recent advances in genomic analysis, information technology, and artificial intelligence should make this medical concept feasible in the near future. In this review, we focused on pre-emptive medicine for hypertension, referring to concrete plans for the future direction of this research. The ultimate goal of pre-emptive medicine is to completely prevent the onset and progression of hypertension by precisely predicting the elevation of blood pressure and performing interventions to avoid it. The diagnostic processes of hypertension, from the standpoint of pre-emptive medicine, should include the detection of abnormal blood pressure regulation as the earliest manifestation of the disease, the depiction of the present status of hypertension in an individual ("nowcasting"), and a prediction of the future trajectory of the disease ("forecasting"). Novel therapeutic strategies for hypertension, from the standpoint of pre-emptive medicine, should aim for the regression of hypertension through early treatments and the remission of hypertension through intermittent intensive therapies. An efficient modification of lifestyle and therapies, according to the progression of hypertension, should be required. If pre-emptive medicine for hypertension becomes established, it would greatly contribute to the extension of a healthy lifespan, which cannot yet be satisfactorily achieved.