MK5 haplodeficiency decreases collagen deposition and scar size during post-myocardial infarction wound repair

ERK3 is involved in regulating cardiac fibroblast function

ERK3/MAPK6 activates MAP kinase-activated protein kinase (MK)-5 in selected cell types. Male MK5 haplodeficient mice show reduced hypertrophy and attenuated increase in Col1a1 mRNA in response to increased cardiac afterload. In addition, MK5 deficiency impairs cardiac fibroblast function. This study determined the effect of reduced ERK3 on cardiac hypertrophy following transverse aortic constriction (TAC) and fibroblast biology in male mice. Three weeks post-surgery, ERK3, but not ERK4 or p38α, co-immunoprecipitated with MK5 from both sham and TAC heart lysates. The increase in left ventricular mass and myocyte diameter was lower in TAC-ERK3+/- than TAC-ERK3+/+ hearts, whereas ERK3 haploinsufficiency did not alter systolic or diastolic function. Furthermore, the TAC-induced increase in Col1a1 mRNA abundance was diminished in ERK3+/- hearts. ERK3 immunoreactivity was detected in atrial and ventricular fibroblasts but not myocytes. In both quiescent fibroblasts and "activated" myofibroblasts isolated from adult mouse heart, siRNA-mediated knockdown of ERK3 reduced the TGF-β-induced increase in Col1a1 mRNA. In addition, intracellular type 1 collagen immunoreactivity was reduced following ERK3 depletion in quiescent fibroblasts but not myofibroblasts. Finally, knocking down ERK3 impaired motility in both atrial and ventricular myofibroblasts. These results suggest that ERK3 plays an important role in multiple aspects of cardiac fibroblast biology.

Exosomes from miR-374a-5p-modified mesenchymal stem cells inhibit the progression of renal fibrosis by regulating MAPK6/MK5/YAP axis

Chronic kidney disease (CKD) in clinical is defined as a gradual loss of kidney function for more than 3 months. The pathologic course of CKD is characterized by extensive renal fibrosis; thus, preventing renal fibrosis is vital for the treatment of CKD. It has been reported that microRNA (miR)-374a-5p was under-expressed in renal venous blood samples from patients with CKD. In addition, it exhibited anti-apoptotic effects in renal tissues suggesting that miR-374a-5p may play an important role in CKD. However, it is not clear whether miR-374a-5p could be delivered to renal cells by exosomes and exerts anti-renal fibrosis effects. To mimic renal fibrosis in vitro, human renal tubular epithelial cell lines (HK-2 cells) were treated by transforming growth factor-β (TGF-β) 1. Reverse transcription-quantitative polymerase-chain reaction (RT-qPCR) or Western blot was carried out to evaluate the mechanism by which miR-374a-5p regulated the development of renal fibrosis. Next, exosomes were isolated using with ultracentrifugation method, and the relationship between miR-374a-5p and MAPK6 was evaluated using dual-Luciferase a reporter assay system. The results indicated TGF-β1 significantly down-regulated the expression of miR-374a-5p in HK-2 cells and miR-374a-5p agomir remarkably inhibited the progression of fibrosis in vitro. In addition, exosomal miR-374a-5p could be internalized by HK-2 cells and obviously enhanced the level of miR-374a-5p in HK-2 cells. Furthermore, exosomal miR-374a-5p prevented the progression of renal fibrosis in vivo by regulating MAPK6/MK5/YAP axis. In conclusion, exosomal miR-374a-5p inhibited the progression of renal fibrosis by regulating MAPK6/MK5/YAP axis.

TLK1-mediated MK5-S354 phosphorylation drives prostate cancer cell motility and may signify distinct pathologies

Metastases account for the majority of prostate cancer (PCa) deaths, and targeting them is a major goal of systemic therapy. We identified a novel interaction between two kinases: tousled‐like kinase 1 (TLK1) and MAP kinase‐activated protein kinase 5 (MK5) that promotes PCa spread. In PCa progression, TLK1–MK5 signalling appears to increase following antiandrogen treatment and in metastatic castration‐resistant prostate cancer (mCRPC) patients. Determinations of motility rates (2D and 3D) of different TLK1‐ and MK5‐perturbed cells, including knockout (KO) and knockdown (KD), as well as the use of specific inhibitors, showed the importance of these two proteins for in vitro dissemination. We established that TLK1 phosphorylates MK5 on three residues (S160, S354 and S386), resulting in MK5 activation, and additionally, mobility shifts of MK5 also supported its phosphorylation by TLK1 in transfected HEK 293 cells. Expression of MK5‐S354A or kinase‐dead MK5 in MK5‐depleted mouse embryonic fibroblast (MEF) cells failed to restore their motility compared with that of wild‐type (WT) MK5‐rescued MK5^−/− MEF cells. A pMK5‐S354 antiserum was used to establish this site as an authentic TLK1 target in androgen‐sensitive human prostate adenocarcinoma (LNCaP) cells, and was used in immunohistochemistry (IHC) studies of age‐related PCa sections from TRAMP (transgenic adenocarcinoma of the mouse prostate) mice and to probe a human tissue microarray (TMA), which revealed pMK5‐S354 level is correlated with disease progression (Gleason score and nodal metastases). In addition, The Cancer Genome Atlas (TCGA) analyses of PCa expression and genome‐wide association study (GWAS) relations identify TLK1 and MK5 as potential drivers of advanced PCa and as markers of mCRPC. Our work suggests that TLK1–MK5 signalling is functionally involved in driving PCa cell motility and clinical features of aggressiveness; hence, disruption of this axis may inhibit the metastatic spread of PCa.

Guidelines for in vivo mouse models of myocardial infarction

Despite significant improvements in reperfusion strategies, acute coronary syndromes all too often culminate in a myocardial infarction (MI). The consequent MI can, in turn, lead to remodeling of the left ventricle (LV), the development of LV dysfunction, and ultimately progression to heart failure (HF). Accordingly, an improved understanding of the underlying mechanisms of MI remodeling and progression to HF is necessary. One common approach to examine MI pathology is with murine models that recapitulate components of the clinical context of acute coronary syndrome and subsequent MI. We evaluated the different approaches used to produce MI in mouse models and identified opportunities to consolidate methods, recognizing that reperfused and nonreperfused MI yield different responses. The overall goal in compiling this consensus statement is to unify best practices regarding mouse MI models to improve interpretation and allow comparative examination across studies and laboratories. These guidelines will help to establish rigor and reproducibility and provide increased potential for clinical translation.

MK2-Deficient Mice Are Bradycardic and Display Delayed Hypertrophic Remodeling in Response to a Chronic Increase in Afterload

Background

Mitogen‐activated protein kinase–activated protein kinase‐2 (MK2) is a protein serine/threonine kinase activated by p38α/β. Herein, we examine the cardiac phenotype of pan MK2‐null (MK2^−/−) mice.

Methods and Results

Survival curves for male MK2^+/+ and MK2^−/− mice did not differ (Mantel‐Cox test, P=0.580). At 12 weeks of age, MK2^−/− mice exhibited normal systolic function along with signs of possible early diastolic dysfunction; however, aging was not associated with an abnormal reduction in diastolic function. Both R‐R interval and P‐R segment durations were prolonged in MK2‐deficient mice. However, heart rates normalized when isolated hearts were perfused ex vivo in working mode. Ca²⁺ transients evoked by field stimulation or caffeine were similar in ventricular myocytes from MK2^+/+ and MK2^−/− mice. MK2^−/− mice had lower body temperature and an age‐dependent reduction in body weight. mRNA levels of key metabolic genes, including Ppargc1a, Acadm, Lipe, and Ucp3, were increased in hearts from MK2^−/− mice. For equivalent respiration rates, mitochondria from MK2^−/− hearts showed a significant decrease in Ca²⁺ sensitivity to mitochondrial permeability transition pore opening. Eight weeks of pressure overload increased left ventricular mass in MK2^+/+ and MK2^−/− mice; however, after 2 weeks the increase was significant in MK2^+/+ but not MK2^−/− mice. Finally, the pressure overload–induced decrease in systolic function was attenuated in MK2^−/− mice 2 weeks, but not 8 weeks, after constriction of the transverse aorta.

Conclusions

Collectively, these results implicate MK2 in (1) autonomic regulation of heart rate, (2) cardiac mitochondrial function, and (3) the early stages of myocardial remodeling in response to chronic pressure overload.

Biallelic truncating variants in MAPKAPK5 cause a new developmental disorder involving neurological, cardiac, and facial anomalies combined with synpolydactyly

PURPOSE

This study aimed to identify the genetic cause of a new multiple congenital anomalies syndrome observed in three individuals from two unrelated families.

METHODS

Clinical assessment was conducted prenatally and at different postnatal stages. Genetic studies included exome sequencing (ES) combined with single-nucleotide polymorphism (SNP) array based homozygosity mapping and trio ES. Dermal fibroblasts were used for functional assays.

RESULTS

A clinically recognizable syndrome characterized by severe developmental delay, variable brain anomalies, congenital heart defects, dysmorphic facial features, and a distinctive type of synpolydactyly with an additional hypoplastic digit between the fourth and fifth digits of hands and/or feet was identified. Additional features included eye abnormalities, hearing impairment, and electroencephalogram anomalies. ES detected different homozygous truncating variants in MAPKAPK5 in both families. Patient-derived cells showed no expression of MAPKAPK5 protein isoforms and reduced levels of the MAPKAPK5-interacting protein ERK3. F-actin recovery after latrunculin B treatment was found to be less efficient in patient-derived fibroblasts than in control cells, supporting a role of MAPKAPK5 in F-actin polymerization.

CONCLUSION

Our data indicate that loss-of-function variants in MAPKAPK5 result in a severe developmental disorder and reveal a major role of this gene in human brain, heart, and limb development.

Colchicine reduces lung injury in experimental acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) is characterized by intense dysregulated inflammation leading to acute lung injury (ALI) and respiratory failure. There are no effective pharmacologic therapies for ARDS. Colchicine is a low-cost, widely available drug, effective in the treatment of inflammatory conditions. We studied the effects of colchicine pre-treatment on oleic acid-induced ARDS in rats. Rats were treated with colchicine (1 mg/kg) or placebo for three days prior to intravenous oleic acid-induced ALI (150 mg/kg). Four hours later they were studied and compared to a sham group. Colchicine reduced the area of histological lung injury by 61%, reduced lung edema, and markedly improved oxygenation by increasing PaO2/FiO2 from 66 ± 13 mmHg (mean ± SEM) to 246 ± 45 mmHg compared to 380 ± 18 mmHg in sham animals. Colchicine also reduced PaCO2 and respiratory acidosis. Lung neutrophil recruitment, assessed by myeloperoxidase immunostaining, was greatly increased after injury from 1.16 ± 0.19% to 8.86 ± 0.66% and significantly reduced by colchicine to 5.95 ± 1.13%. Increased lung NETosis was also reduced by therapy. Circulating leukocytosis after ALI was not reduced by colchicine therapy, but neutrophils reactivity and CD4 and CD8 cell surface expression on lymphocyte populations were restored. Colchicine reduces ALI and respiratory failure in experimental ARDS in relation with reduced lung neutrophil recruitment and reduced circulating leukocyte activation. This study supports the clinical development of colchicine for the prevention of ARDS in conditions causing ALI.